Note: Descriptions are shown in the official language in which they were submitted.
1310~88
20365--2904
OPERATI~NAL HET~OD AND CONTRQL SWITCHING APPARATUS FOR
MONITORING THE STARTING-CY~LE CIRCUIT ~F ELECTRIC HIGH-VOLTAGE
HOTORS WITH ASYNCHRONOUS ST~RT-UP
BACKGROUND OF THE INVENTION
The present invention relates to an operational
method for electric motors, whereby the rotational speed of the
rotor and the power input are calculated and the temperature-
rise values are stored. These temperature-rise val~es
represent the relative temperature-rise condition of the motor,
when the motor is operated under diverse rotational speeds and
load conditions. A temperature~rise value is assigned to each
designated operating mode and, based on the rotational speed of
the rotor and the power input, it is periodically determined,
in which of the designated operating modes the motor is
currently running.
In the case of a known method, operating modes are
configured for each steady-state operating condition of the
motor. These operating modes are defined by the rotational
speed and the power consumption of the motor. Temperature-rise
values are assigned to these operating modes and are then
compiled, together with the operating mode of the motor and,
consequently, the elements of the temperature-rise condition
matrix are determined, for example, from the value pairs, which
are rotational speed and moment of rotation. By evaluating the
signals of a sensor, operating as a tachometer, and the
operating angle of the electronic controlling system, provided
to adjust the power input of the motor, the rotational speed
and power consumption or moment of rotation are determined.
Each operating mode, defined by the rotational speed
and the operating angle, is assigned a temperature-rise value,
1 310688 20365-2904
calculated empirically, which is stored in a first storage
unit. Thereby, the stored temperature-rise values range from
positive to negative values. Positive temperature-rise values
are stipulated, if the temperature of the motor rises in an
operating mode, while negative temperature-rise values are
assigned to operating modes with falling temperatures. The
value zero is designated for constant motor temperatures. In
the known procedure, a monitoring device periodically compares
the temperature-rise condition matrix stored in the first
storage unit with the actual operating mode, on the basis of a
processor unit, and the appropriate temperature-rise values are
input in a second storage unit and added to an accumulated
total value. When a predetermined upper limit value for the
storage unit is exceeded, it is assumed that the motor is
overloaded, based on the actual operating condition. On the
other hand, one assumes normal operating conditions, when the
storage unit is below a predetermined lower limit.
The known operating procedure i5 especially intended
for machine-tool motors and their overload protection, whereby
very small motorsr especially universal motors, are used. As a
rule, these motors have a power supply controlled by electronic
components. The known operating procedure can be integrated in
its control engineering plan without entailing additional
expenditure, since an electronic load regulation is provided.
Furthermore, the operation of machine tools, for example, hand
drills and the like, is accompanied by constantly changing
stress with variable driving tor~ues. These require, however,
only a modest driving power, so although an expensive automatic
control is necessary, it can be realized with relatively low-
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1 I cap~clty componentS.2 ji As a rule, small universal motors are used in these
3 ll types of low-capacity machine tools, whereby the injected
4 ~I current is carried over the stator, as well as over the rotor,
1¦ so that the current flowing in the rotor equals the injected
6 1¦ current. Therefore, the rotor current can be immediately
7 1I determined by measuring the stator current. The spectrum of
8 ll operating modes of this type of universal motor ranges, in the
g l case of small hand machine tools, from standstill over start-
0 1 1 Up! to full load, idling, running down, etc., whereby very
~ diversified combinations of rotational speed and rotor current
12 l ¦ can also occur. The temperature rise in such a motor during
13 1 ¦ start-up operation is hardly different than during an operation
14 ¦ ¦ in a stalled state. Furthermore, there are no special rotor
,ll parts, which are stressed or endangered by starting operations
16 l¦ alone.
17 'l on the other hand, when large high-capacity, high-
18 ¦¦ voltage electric motors are used, for example, to drive wood-
19 ¦¦ proces~ing machines (refiners), compressors, ventilators, pumps
i I or mills, it is not practical to regulate the supply power with
21 'I electronic means in most cases. This is due to the fact that
22 ~ the expenditure would be too high, as a result of the large
23 1 1 amount of power required to operate these motors. Therefore,
24 ¦ I these types of large motors are usually designed as high-
I voltage asynchronous or synchronous motors.
26 ¦' Such large electric high-voltage motors are generally
27 ,~ started up asynchronously from the mains. Either a special
28 ~ starting windingJ such as, for example, a cage winding may
29 ~ serve for this purpose, or certain parts of the available rotor
winding, for example, the upper part of the tapered deep-bar
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l ll cages in a tapered deep-bar cage rotor winding or the top bar
2 ll of a double-cage rotor winding, can be stressed during start-
3 ~l up. In addition, however, the rotor body itself or parts of it ¦
4 l, can be used to carry the induced currents, which occur during
ll asynchronous start-up, without a distinct rotor winding or
6 1! specific rotor winding part being present. For this purpose,
7 ~l for example, non-laminated subsections of the rotor body, which
8 ll allow eddy currents to form, when there is an asynchronous
9 ~¦ start-up inside the rotor, can be useful. In these types of
l¦ slipringless high-voltaqe motors, the rotor starting losses,
~ which are in proportion to the starting torque, are virtually
12 ll completely converted inside the rotor starting windings or
l3 ll rotor winding parts, respectively, in the rotor body or in the
14 ¦I rotor body parts. Contrary to the slipring motors, the
li conversion of the starting losses does not take place in the
16 1 external starting resistors. Instead, it occurs mainly inside
17 1 the rotor itself, which is why the previously mentioned,
18 1 affected parts heat up a great deal during start-up.
l9 ¦~ In comparison with a small machine-tool motor, the
l start-up of a large high-voltage motor does not represent a
21 ¦ ¦ normal operating condition. It is a transient process, as set
22 ll forth in the British standards for electric machines, British
23 1~1 Standard 5000, Part 16, 1981, Art. 10, paragraph 1. For the
24 ll most part, this transient process only stresses the rotor parts
ll in the high-voltage motor, which are affected during
26 ¦ asynchronous start-up. Therefore, the total thermal load
27 capacity of the high-voltage motor in starting operations is
28 determined by the load capacity of these parts.
29 llA control switching operation to monitor the
operating temperature of an electromotor, especially a
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13101;8~
1 ¦¦ machine-tool universal motor, is also known from
2 ~l E-Bl OO 33 161. However, this control switching operation only ¦
3 1~ consid~ers actually occurring operating conditions, which have
4 '¦ been asæigned empirically calculated temperature-rise values.
'll Specific details on circuit construction are not provided
- 6 1 ¦ concerning the special stresses that a large high-voltage motor
7 ~l is subject to during the transient asynchronous start-up
8 ll process, and the thereby occurring, time-dependent heating or
g ¦I cooling of the rotor parts, affected during start-up; nor does
I the known control switching operation go into details
concerning the conditions, under which such a large high-
12 I voltage motor is operated. Furthermore, the known control
13 ~ switching operation cannot consider the interests of plant
14 1¦ management, especially relative to the frequency and marginal
,¦ conditions of starting operations, because said control
16 ¦ I switching operation is conceived on the basis of an
17 1 ¦ electronically regulated power input for a small machine-tool
18 ¦ I universal ~otor.
19 I Contrary to a small machine-tool universal motor, in
1 asynchronous starting operations of a large high-voltage motor,
21 1 the conditions, under which the start-up itself takes place,
22 ¦ I must be particularly considered. This is due to the fact that
23 ¦~ the rotational speed and current characteristics have the most
24 ll important effect on the loading of the parts affected during
'¦ start-up and determine their thermal stress.
26 ,l The operating procedure for such electric high-
27 l~ voltage motors must, therefore, consider that the power supply
28 ll can only be switched on or off, thus there is no externally-
29 ll commutated automatic control of the motor power. For physical
reasons, the therral loading capacity of the starting winding
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13101~88
1 ~ Of such a high-voltage motor is time-limited. As far as
2 1 conditions during asynchronous start-up are concerned, there is !
3 ¦ I a danger of thermally overloading parts affected during start- ¦
up. This is especially true in large high-voltage motors,
'j since the parts cannot be designed for constant starting loads.
6 jl Also, the machines to be driven often have a very high
7 ,I counter-torque or can even stall if the motor blocks. This
a ~1 I means that the current flow in the starting windings can last a
9 1, long time on a different level.
1~ SUMMARY OF THE INVENTION
11 ll An object of the present invention is to provide an
12 ,¦ operational method for large electric higb-voltage motors,
13 ll especially for those with an asynchronous automatic start-up,
14 il which, using simple means, detects the starting conditions,
ll even in the case of a complicated start-up or a stalled motor,
16 1l and which insures an overload protection of the rotor parts
17 ¦1 affected during asynchronous start-up. Thus, the start-up rate ,
18 ll of occurrence is orientated to the individual thermal loading
19 ¦I capacity of these parts and is limitsd by it. In addition, one
Ij should be able to determine the operating state of the high-
21 ~¦ voltage motor by acquiring as-few-as-possible, easily
22 ¦¦ accessible variables. Also, installing this protective feature
23 ~ should not restrict the availability of this important capital
24 1 item.
I The above and other objects of the invention are
26 ~i achieved by an operational method for an electric motor,
27 I whereby the rotational speed of the rotor and the power input
28 1 are calculated and the temperature-rise values are stored.
29 ,I These temperature-rise values represent the relative
temperature-rise condition of the motor, when the motor is
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1 jl operated under diverse rotational speeds and load conditions.
2 1l A temperature-rise value is assigned to each designated
3 ¦ operating mode and, based on the rotational speed of the rotor
4 ,l and the power input, it is periodically determined, in which of ¦
5 1 ¦ the designated operating modes the motor is currently running,
6 1 ¦ whereby, to protect asynchronously starting high-voltage
7 1 ¦ motors, with a conversion of the starting losses, mainly inside
8 ll the rotor, from overloading during start-up or, in a stalled
g ¦¦ state, to determine the through-rating in the rotor, only the
,! stator winding current is measured. The number and the
11 I duration of the starting operations of the high-voltage motor
12 1l are monitored and the dynamic heating and cooling of the rotor
13 j parts affected during start-up, during the starting operations,
14 1 the different operating conditions, slowing operations and
1 stoppageæ are each represented by specific discrete value
16 1~ combinations, which take into account the time lapse of all
17 ll these transient and steady-state operating conditions and
18 Ij stoppages, as well as the thereby occurring stator current and
19 1I the rotational speed of the rotor. These value combinations
~ are in the form of temperature-rise condition matrices of the
21 1 1 affected rotor parts and operational condition matrices of the
22 ~ high-voltage motor. From these are derived heating and cooling
23 1l values of the affected rotor parts. They are added with
24 1l opposite signs to an accumulated total value, stored and
l¦ registered. This total value determines how many starting
26 l~ operations are still possible, and that with a specific first
27 value of the accumulated total value, the motor is switched off
28 l and that any switching-on is prevented by an inhibiting
29 ~ll function, as long as the accumulated total value has not
~ reached a specific second value.
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l 1l Using an operational method of the type mentioned in
2 1¦ the beginning, the objective is solved, according to the
3 Il invention, by measuring only the stator winding current to
4 ¦I determine the through-rating in the rotor. This is done to
! ! protect asynchronously starting high-voltage motors, with a
6 ~¦ conversion of the starting losses, mainly inside the rotor,
7 I from overloading during start-up, or in a stalled state, only
8 ¦ I the stator windin~ current is measured, to determine the
g !~ through-rating in the rotor. The nu~ber and the duration of
¦ the starting operations of the high-voltage motor are monitored
ll I and the dynamic heating and cooling of the rotor parts affected
12 during start-up, during the starting operations, the different
13 I operating conditions, slowing operations and stoppages are each
14 represented ~y specific discrete value combinations, which take
1 into account the time lapse of all these transient and steady-
16 I state operating conditions and stoppages, as well as the
17 ¦ I thereby occurring stator current and the rotational speed of
18 1~ the rotor. These value combinations are in the form of
l9 ¦I temparature-rise condition matrices of the high-voltage motor.
¦~ From these are derived heating and cooling values of the
21 ll affected rotor parts. They are added with opposite signs to an
22 ¦1 accumulated total value, stored and registered~ This total
23 I value determines how many starting operations are still
24 1 possible, and that with a specific first value of the
¦ ¦ accumulated total value the motor is switched off, and that any
26 I switching-on is prevented by an inhibiting function, as long as
27 ll the accumulated total va ue has not reached a specific second
28 I value.
29 This procedure makes it possible to consider a
,I theoretical temperature-rise model for the time-dependent,
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131OD88
1 1, dynamic heating and cooling of the parts affected during
2 1I start-up in the rotor of a large high-voltage motor for all
3 jl steady-state and transient operating conditions and, above all, I
4 1I for the transient operation of the asynchronous start-up. For
il this purpose, the number and the duration of the starting
6 ¦ ¦ operations, the thereby occurring currents in the stator, as
7 ll well as the rotational speed of the rotor are registered and,
8 ¦j based on these transient operations, as well as the occurring
g l¦ operating conditions, such as idling, rated operation, slowing
~¦ down, stalling, standstill, or also data pertaining to known
11 ll operating conditions, they are entered into the theoretical ¦-
12 ll temperature-rise model, and criteria are derived to form
13 ¦ discrete heating and cooling values of the rotor parts affected
14 ll during start-up. Thereby, it is also considered, that the
I heating and cooling values correspond to time-dependent heating
16 ¦1 and cooling Punctions, which are determined by the theoretical
17 ¦! temperature-rise model. This means that the fact, whether the
18 I high-voltage motor runs or stands still during heat
19 ¦ dissipation, is also fully entered into the operating
procedure.
21 ll Altogether, all the input data that the operating
22 ¦ 1~ procedure requires are the rotational speed, the stator current
23 1~ and the time duration (or the starting operations or the
24 ¦ steady-state operating conditions, the slowing operations and
I the stoppages), in order to continuously determine therefrom,
26 with the help of the theoretical temperature-rise model, the
27 ll temperature-rise condition of the rotor parts affected during
28 start-up. It i5 not necessary to measure the energy converted
29 1 in these parts. In large high-voltage motors, this would
require temperature ~ensors or current-measuring devices in the
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131~S88
1 ¦ normally not accessible rotor parts, which are affected during
2 ¦ start-up. The measured values of these sensor~ or devices
3 I would have to be passed along from the rotating rotor over
4 I sliprings or other transmitting means to stationary parts, for
,l example, in order to be able to measure the current flowing
6 ,1 into them and, thereby, to be able to be close to their
7 I converted power loss. Thus, an additional constructional
8 l, expense is avoided in the monitoring of the temperature-rise
g li condition of the rotor parts of the high-voltage motor affected
1~ during start-up.
11 l The steady-state and transient operating conditions,
12 ¦I which occur, are catalogued in the form of operating condition
13 ,I matxices, which are made up of the elements stator current and
14 1i rotor rotational speed or stator current and conduction
l interval. They also contain the transient operations,
16 ¦ I especially the starting operations. With the help o~ the
17 ll theoretical temperature-rise model, temperature-rise condition
18 1 ll matrices are formed for the rotor parts affected during start- i
19 1¦ up, which contain the elements stator current, rotor rotational
l, speed and conduction interval, as well. Moreover, they contain
21 ,I the heating and cooling values resulting from the theoretical
22 ll temperature-rise model, which correspond to the time-dependent
23 ,I heating and cooling functions. During start-up, operation and
24 1I standstill, and also in the case of a stalled high-voltage
ll motor, values are selected from the operating condition
26 i matrices, based on the actual operating condition data, and are
27 1 ¦ each assigned to the elements of the temperature-rise condition
28 ll matrix. In this way, specific heating or cooling values are
29 l selected. This selection process for heating and cooling
values takes place periodically.
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1 1l The heating values, which are derived periodically,
2 ' are continuously added with a negative sign and the cooling
3 l' values with a positive sign, to an accumulated total value.
4 ;I Thus an actual, discrete value, which is inversely proportional
5 ll to the temperature-rise condition of the rotor parts affected
6 ll during start-up, is constantly present.
7 1 Based on the end result of the accumulated total
~ 1I value, an estimation can be made of the total possible starting
9 ! operations, which are still available without overloading: for
ll one start-up, for example, a specific measure of discrete
11 ¦I values is provided, which rapidly lowers the level of the
12 11 accumulated total value. During those operating conditions or
13 l! stoppages, in which the starting windings cool down, the
14 I I discrete values, which are inversely proportional to the
li cooling, are graded in finer steps. This slowly raises the
16 j ¦ level of the accumulated total value up to a previously
17 ¦ established maximum value, which, at the same time, indirectly
18 1~ establishes the maximum number of starting operations. If the
19 l! accumulated total value indicates a level, which is less than
1I the required measure for a start-up, then one will realize that
21 11 ! no additional start-up can be performed. A start-up only makes
22 ll sense, if the level of the accumulated total value is
23 1 sufficient, after the rotor parts affected during start-up,
24 l¦ have cooled down.
25 l l Among other factors, the procedure also considers
26 j I that a very effective cooling takes place during the no-load
27 l operation of the high-voltage motor, so that the accumulated
28 l total value rises again very quickly. As a result, one can
29 read off from the indicated level of the accumulated total
30 I value, if it is possible to initiate a renewed start-up under
, ~ .
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1 ¦ load conditions.
2 ¦ In addition, a minimum value is defined for the
3 ¦' accumulated total value, at which a break in the stator current
4 ,l is released. An interlocking device ensures that a renewed
~I start-up can only take place, if the accumulated total value
6 1 I shows a sufficiently high level. It can be advantageous to
7 ! ~ select elements of the operating condition matrices from the
8 ll last slow-down operation and, from these elements, to
g 1l predetermine and also display temperature-rise values for the
ll next start-up. This provides the plant management with some
~ flexibility, which is especially advantageous for controlling
12 ll the driving mechanisms of large wood-processing machines
13 1 ¦ (refiners). Based on the indicated level of the accumulated
14 1I total value and the additional display of the change in this
l~ level to be expected at the next start-up, the plant personnel
16 I can decide which type of further speration is still possible
17 ! and which one offers the greatest efficiency, without, however,
18 1 endangering the high-voltage motor. In this way, for example,
l9 1 by quickly unloading the refiner after an unsuccessful heavy
ll I starting, a start-up without load can be implemented with a
21 lll subsequent highly cooling no-load operation, so that the high-
22 ll voltage motor cools down very quickly and is ready for a new
23 ¦! start-up under load. In this way, one can avoid operating
24 ~I stoppages, which can result from long cool-down phases of the
2S ll high-voltage motor and can lead to long down-times, especially
26 l in wood-processing processes in paper factories.
27 I f It can also be advantageous, if the accumulated total
28 ,ll value is displayed in natural, whole numbers. This type of
29 ¦ representation of the accumulated total value makes it easily
1 possible for the plant personnel to follow the actual
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1 l~ temperature-rise condition of the rotor parts affected during
2 ¦I start-up and, consequently, the operating readiness of the
3 ll ! high-voltage motor, and to set-up plant management accordingly.
4 i Moreover, it can be advantageous, if additional
~j threshold values of the stator current and of the rotor's
6 1I rotational speed are defined, which act as a criterion to
7 1 I release transformed functions and are superimposed on the
8 il accumulated total value. In this way, additional criteria,
g 1l which provide additional information for plant management, are
1I formed, under consideration of the temperature-rise condition
11 1 of the high-voltage motor, based on specific values of the
12 ~I stator current and of the rotor's rotational speed. For
13 ¦¦ example, when the motor is at a standstill (rotor rotational
14 l ¦ speed = O), and there is a full stator current at the same
1 ! time, one can recognize that the motor is apparently stalled,
16 ¦¦ so that it is necessary to discontinue the start-up, although
17 ¦ the heating of the rotor parts affected during start-up would
18 not yet make this necessary. The necessity of discontinuing
19 the start-up would not be recognizable solely by evaluating the
1l level of the accumulated total value.
21 An especially advantageous further embodiment of the
22 invention relates to a control switching operation to implement
23 ~I the previously mentioned operational method concerning an
24 ¦~ asynchronously starting electric high-voltage motor, with a
1¦ conversion of the starting losses, mainly inside the rotor, to
26 ll protect it from overloading during the asynchronous start-up or
27 ¦ I in the stalled state. The control switching operation
28 ~ comprises a rotational-speed sensor to determine the rotational
29 ! speed of the high-voltage motor and to generate a first input
ll signal, proportional to the rotational speed. It also
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1310S~8
1 1¦ comprises a first digital storage means to store operating
2 j~ condition matrices of the high-voltage motor and temperature-
3 ~l rise condition matrices of its rotor parts affected during
4 ,¦ start-up. In addition, it contains a digital processing unit
ll to read in, process and output digital signals, as well as to
6 ll select the appropriate heating and cooling values for the rotor i
7 1 I parts affected during start-up, according to the actual
8 11 operating condition of the high-voltage motor from the first
g l¦ digital storage means, as well as a second digital storage
!~ means to store the accumulated total value, made up of heating
11 1l and cooling values, corresponding to the temperature-rise
12 ¦~ condition of the rotor parts affected during start-up.
13 I Furthermore, according to the invention, the control
14 'I switching operation is characterized by a measuring device,
I which determines the stator current and generates a digital
16 '¦ current signal proportional to this, and a counter, both of
17 jj which are connected to the processor unit. The counter is
18 '! started or stopped or set back, in accordance with the actual
19 l¦ operating condition data of the high-voltage motor, derived
li fro~ the digital rotational speed and current signals. The
21 l¦ operating condition matrices and temperature-rise condition
22 Ij matrices for the first digital storage means contain value
23 ~I combinations of the stator current, rotational speed and
24 ¦I counter status. Also, the processor unit forms value
1, combinations, based on the actual digital stator current
26 l~~ signals and digital rotational speed signals supplied to it,
27 ll and also based on the counter content fed to it. The processor
28 1 unit also selects corresponding value combinations of the
29 . operating condition or temperature-rise condition matrices from
the first digital storage means which is connected to it. From
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1 ~! these, the processor unit derives discrete heating and cooling
2 ll values and reads them into the second digital storage means,
3 ~l' which is connected to the processor unit. Means are provided
4 ll to discontinue the start-up and to automatically control the
1I starting sequence. These means are connected to the processor
6 ¦¦ unit and to a switching device to interrupt the stator circuit
7 l! of the high-voltage motor. The breaking operation and the
8 1l automatic starting sequence control result, hereby, according
9 ~¦ to the contents of the second digital storage means. Also, the
~¦ position of the switching device is signalled back to the
~ processor unit by signalling devices. First display devices
12 !, are provided, which are linked over the processor unit with the
13 ll second digital storage means.
14 ll BREIF DESCRIPTION OF THE DRAWINGS
1 In the following, the invention will be described in If
16 ll greater detail, based on a simplified exemplified embodiment,
17 ll represented in FIGS. 1 to 3 of the drawing, which depicts the
18 ¦~ start-up monitoring of large electric high-voltage motors.
19 l~ With reference to the drawings,
ll1 EIG. 1 illustrates a simplified example of an
21 l! operating condition matrix;
22 l' FIG. 2 is a graphic representation of a start-up
23 ll example of the operational method, in the form of an
2 4 ¦ I operational sequence chart; and
~I FIG. 3 illustrates a simplified block diagram for a
26 1l control switching operation to implement the operational
27 ~ method.
28 li DETAILED DESCRIPTION:
29 ~I Generally, electric high-voltage motors are started
l~ asynchronously from the mains. In the case of slipringless
1,
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1 'I high-voltage motors, a special starting winding, such as, for
2 ll example, a cage-winding, serves for this purpose. Certain
3 ll parts of the available rotor winding, for example, the upper
4 ll part of the tapered deep-bar cages in the case of a tapered
l' deep-bar cage winding or the top bar of a double-cage winding,
6 1 I can also be stressed during an asynchronous start-up. It is
7 ~ also possible, however~, that non-laminated parti~ of the rotor
8 1 I body, or the rotor body itself, can be used to guide currents
g l¦ in the rotor, which occur during start-up, in which the rotor
1I power loss, which is proportional to the starting torque, is
11 I converted.
12 l l This asynchronous start-up leads to a very intense
13 l¦ heating of the parts of the rotor affected during start-up.
14 lI This heating is not accessible to a direct measurement,
15 1 I however, as a result of the present operational method, it can
16 be considered. The starting point of the operational method is
17 I the operational condition matrix shown in FIG. 1. It
18 ¦1 illustrates combinations of the measured stator current Il,
19 1I rotor rotational speed n and time duration t of the starting
1 operations; steady-state operating conditions, slowing
21 ~ operations, and stoppages. Furthermore, some threshold values
22 ~ for the stator current I1, and the rotor rotational speed n are
23 ~ still defined, which are drawn upon as additional criteria to
24 ll assess each operational or starting, slowing or standstill
25 1I condition, at hand, and which facilitates the selection of an
26 l assigned temperature-rise value, which is used to form the
27 l accumulated total value. A limit speed nO, which corresponds
28 1I to approximately 10% of the nominal rotational speed of the
29 I high-voltage motor, and the nominal current IN are definded as
'~ additional values.
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1 ll The following combinations result from the
2 ll operational condition matrix shown in FIG. 1: If the stator
3 ! ' current Il = 0 and the rotational speed n is less than the
4 ~l limit speed nO, then there is a stoppage. On the other hand,
li if the rotational speed n is greater than or equal to the limit !
6 1 ¦ speed nO and the stator current Il = 0, then the high-voltage
7 1~ motor is in slowing operation. If the stator current Il is
8 ,¦ greater than 0 and less than 1.2 times the nominal current IN,
g ¦I then, in the case of an actual rotational speed n, which is
l¦ less than the limit speed nO, then the high-voltage motor is
~ starting up with too low a switching error, a cut-off is
12 1 I provided, as soon as the conduction interval exceeds a
13 ¦ I predetermined value t1. If, on the other hand, the rotational
14 1I speed n is greater than or equal to the limit speed nO, then
15 !' the normal operating condition exists, so that it is not
16 1~ necessary to interrupt the operation as a result of a possible
17 ¦ overheating of the starting windin~ or starting winding parts.
18 l I For the case that the stator current Il is greater
19 1I than or equal to 1.2 times the nominal current IN and, at the
¦¦ same time, the rotational speed n is less than the limit speed
21 ~I nO, then it i5 obvious that ther~ has been a switching-on with
22 ! I a stalled rotor, so that a cut-off must follow, if the
23 ¦I conduction interval exceeds a predetermined second value t2.
24 ~¦ If, on the other hand, the rotational speed n is greater than
~ the limit speed nO, then, in the case of such an increased
26 ~I stator current Il = 1.2 IN, there is a start-up under severe
27 l operating conditions, so that , if after exceeding a third
28 !I predetermined time t3, an increased stator current Il = 1.2 IN
29 'I continues, the start-up operation must be interrupted.
1 In the case of the operational method, accordin~ to
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1 l~ the invention, the times t1, t2 and t3 are variable values.
2 ll These values are determined from the logical evaluation of the
3 1 I stator current I, after a stipulated time to. Furthermore,
4 I based on the knowledge of the theoretical temperature-rise
model of the rotor parts affected during start-up, time-
6 1I dependent heating or cooling functions are established for each
7 1, operating condition of the high-voltage motor.
8 1 I By combining the elements of the operating condition
g 1¦ matrix, depicted as an example in FIG. 1, with the calculated,
l~ time-dependent heating or cooling functions of the affected
11 11 rotor parts, a temperature-rise condition matrix, not shown
12 ¦ I here, is set up. With this matrix, discrete heating or cooling ¦
13 ~¦ values are defined, which consider the time dependency of the
14 ll ~ temperature-rise condition of the rotor parts affected during
11 start-up.
16 ~l Thus a chronological sequence of heating or cooling
17 ¦I values is assigned to each steady-state and, above all, to each
18 , transient operating condition of the high-voltage motor, which
19 ~ enables the dynamic thermal characteristic of the rotor parts
1 affected during start-up to be determined.
21 ¦ Based on the operating condition matrix, heating or
22 1 cooling values can thus be selected from the temperature-rise
23 jI condition matrices and added to an accumulated total value and
24 ¦I stored. In the continuation of the operational method, the
'I temperature-rise condition, valid at any one time, of the rotor '
26 l~ parts of the motor affected during start-up is represented by a
27 11 display of the accumulated total value. This representative
28 l`, value is presented in the form of natural numbers and extends
29 ~ to the temperature-rise condition of the rotor parts affected
during start-up. It is also constantly dynamically determined
Il
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i' .
,
ll
1 1 during the changeover from one operating condition to the
, other, whereby transient transition conditions and, thereby,
3 ¦ especially the start-up, are also considered.
4 1I FIG. 2 depicts an example of the operational sequence
ll of a high-voltage motor, whereby its rotor parts affected
6 ! I during start-up are protected according to the operational
7 1I method of the invention. On the abscissa, the time t is
8 1 represented in hours, and on the ordinate, the accumulated
g Ij total value is displayed in the negative direction with numbers i
j~ from 30 to 0. Assuming an operation lasts several hours, the
ll !I rotor of the high-voltage motor constantly heats up, so that
12 ¦I the starting winding also shows a definite temperature-rise
13 ¦I value, corresponding to the constant temperature-rise condition
14 1~ in the steady-state operating condition l. This value is 20.
il At the four-hour mark, as represented, the motor is switched
16 11 off and slows down in a short time, until it reaches
17 1 standstill. The starting winding cools off, thereby, in
18 ¦ accordance with its standstill cooling function 2, and after
19 1 approximately 2.5 hours, a value of 25 is obtained for the
1 accumulated total value. If a new start-up is initiated now,
21 after 6.5 hours, and a rotor is stalled, then this is
22 ¦¦ determined by analyzing the operating condition, this means by
23 1 I comparing the actual operating condition data to the stored
24 ¦ I operating condition matrices. The starting operation is then
~ immediately interrupted. The indicated accumulated total value
26 1I diminishes after that by the value lO to 15. A heavy starting
27 ll follows, and after its successful completion, the indicated
28 value of the accumulated total value falls to zero.
29 ' Since the motor runs subsequently in a normal,
li steady-state operating condition, for the time-being, a delay
1, 1 ,.
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~ 131(~8
1 l! time 3 is considered for the temperature distribution within
2 ! I the rotor, and the accumulated total value is kept constant.
3 ll After approximately one hour of operating time, cooling values,
4 jl corresponding to the operational cooling function 4, are
I supplied to the accumulated total value, so that its display
6 1I rises again relatively quickly.
7 l If, after a total of 8 hours, the motor is switched
8 ll Off and slows down and then comes to a standstill, then the
g ll display of the accumulated total value only rises slowly, in
11 accordance with the standstill cooling function 2.
11 li If the accumulated total value reaches a sufficient
12 ¦ level again, then renewed start-ups can be performed. Thereby,
13 ll the operating cooling function 4 and also the standstill
14 ! ~ cooling function 2, as well as the constant temperature-rise
5 ¦I condition in the steady-state operating condition 1, are
16 ~I considered. When the motor is completely cooled off, as shown
17 1 in the operational sequence chart in Fig. 2, a total of three
18 1 normal start-ups are possible, one after the other, at the 22-
19 ¦ hour mark. These start-ups can be effected without causing the
¦ rotor parts affected during start-up to be overloaded or, on
21 i the other hand, without improperly restricting the availability
22 ! 1 of the high-voltage motor.
23 ll As depicted in the operational sequence chart in Fig.
24 ll 2, a simple control is provided for the temperature-rise
¦I condition of the rotor parts of the high-voltage motor affected
26 ll during start-up. This control results from operating condition
27 1l data consisting of a stator current I1, rotor rotational speed
28 l n, as well as the times t for the various starting, operating
29 ll and standstill conditions, in combination with the heating and
~ cooling functions 2.4, valid at any one time, acquired from the
' I
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1 I theoretical temperature-rise model of the rotor winding. This
2 I makes it possible to have a safe, but also flexible, plant
3 'l management, that will be able to make decisions with foresight,
4 1 in order to achieve the best-possible availability of the
ll high-voltage motor. This enables a method of operation to be
6 sustained, in which, after a failed start-up at 5.5 hours, for
7 1l example, one can quickly transfer over to the normal operating
~ ll condition with a good cooling function, by immediately
g ll executing a second start-up of the high-voltage motor.
ll The previously described exemplified embodiment of
the operational method for a large high-voltage motor can be
12 1, accomplished with the control switching operation depicted,
13 ll greatly simplified, in FIG. 3, in the form of a block diagram.
14 j For this purpose, a sensor working as a tachometer 31
l~ is provided on the high-voltage motor 30 and a stator current
16 ll measuring device 33 is provided in the stator ci~cuit 32 of the
17 1 I high-voltage motor 3~; both transmit their data to a processor
18 ¦1 unit 34. A time standard or clock 35 is also provided to
19 ll standardize a counter 35, which is connected bidirectionally to i
, the processor unit 34 and is reset, started, ~topped and tested
21 il by the processor unit. In a ~irst digital storage 37, which is
22 ll connected to the processor unit 34, operating condition
23 1 I matrices 39, 40 are stored, which consist of v~rious single
24 li data collections and contain a stator current/time - operating
¦~ condition matrix 39 and a stator current/rotational speed -
26 ll operating condition matrix 40. In addition, a temperature-rise
27 1¦ condition matrix 41, dependent on the stator current Il,
28 , rotational speed n and time t parameters, is stored in the
29 1, first digital storage 37. This matrix is formed on the basis
of the occurring start-up, operating, slowing and standstill
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1 ll conditions of the high-voltage motor 30, in accordance with the
2 I operating condition matrices 39, 40. The temperature-rise
3 ll condition matrix 41 contains the dynamic, time-dependent
4 ll temperature-rise behavior of the rotor parts of the high-
ll voltage motor 30 affected during start-up, in the form of
6 ll temperature-rise and cooling values or heating and cooling
7 ¦¦ functions 2.4, assigned to the elements of the operating
8 ll condition matrices 39~ 40 (see FIG. 2).
9 , The processor unit 34 selects the time-dependent
1 heating and coolinq values from the temperature-rise condition
11 ¦ matrix 41 by comparinq the actual operating condition data on
12 1! rotational speed 31, stator current 33 and time measurements,
13 acquired by the counter 36, to the data in the operating
14 lj condition matrices 39, 40.
l l A second digital storage 42 is connected to the
16 1 I processor unit 34. The heating and cooling values ~rom the
17 1l processor unit 34 are read into and stored in the storage
18 1 means, whereby the accumulated total value is formed. since
.~ the heating and cooling values of the rotor parts of the high-
~ voltage motor 30 affected during start-up are each added with
21 1~ an inverted sign in the digital storage 42, its contents
22 ~I correspond exactly to the actual temperature-rise condition of
23 ¦ these rotor parts of the high-voltage motor 30, affected during
24 ll start-up. The contents of the digital storage 42 are converted
ll by the processor unit 34 into numerical values of natural
26 I numbers and presented by means of a first display device 43,
27 ~l which is connected to the processor 34. A second display
28 device 44, supplied by the processor unit 34, is also provided,
29 l~ so that the actual operating condition of the high-voltage
I motor 30 can be monitored with the display of the acquired
.
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1 ¦¦ values Il and n.
2 1 ¦ A third display device 45 is connected to the
3 I processor unit. It displays the change in the accumulated
4 jl total value, which is to be expected with the next start-up and ¦
¦l is predetermined on the basis of the last slowing operation
6 ¦I from the operating condition matrices 39, 40 and the
7 1~l temperature-rise condition matrix 41. In this way, the plant
8 1 I personnel can very easily read off, which temperature-rise
g ¦¦ value the parts of the rotor affected during start-up would
¦¦ have after the next start-up. They could then alleviate the
starting conditions of these parts using appropriate preventive ¦
12 I measures, for example by relieving the high-voltage motor 30.
13 ! In addition, start-ng interruption device 46 and
4 1 ¦ automatic starting sequence control device 47, are connected to ¦
5 ! I the processor unit 34 and controlled by it, according to the
16 ¦~ temperature-rise condition of the rotor parts of the high-
17 ¦¦ voltage motor 30 affected during start-up, thus according to
18 1 the me~ory contents of the second digital storage 42. In
19 ¦ addition, the switching arrangement 48 is connected by a
1 signalling circuit 49 with the processor unit 34. A fourth f
21 ¦ display device 50, which is connected to the processor unit 34
22 !1 as well, indicates the position of the switching arrangement 48
23 l! and, in addition, makes it easier for plant personnel to
24 ¦I monitor the operating condition of the high-voltage motor 30.
ll The accumulated total value, stored in the second
26 j¦ digital storage ~2, represents the temperature-rise condition
27 ll of the rotor parts of the high-voltage motor 30 affected during
28 1I start-up. On this basis, when the value falls below a
29 1 I previously established threshold value, the processor unit 34
I initiates the device 46 to interrupt the start-up, whereupon
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1 ' the switching arrangement 48 interrupts the stator current I1.
2 1 Since the accumulated total value and, therewith, the contents
3 1 of the second digital storage 42 and the operating condition
4 1 l analysis, i.e., the comparison between the actual operating
5 ll I condition data Il, n and t with the data stored in the first
6 11 digital storage 37, also considers, above all, starting
7 ll operations, the interruption of the stator circuit 32 is also
8 l~ provided, already before a starting operation. Thereby, the
g ll parts are protected, which are stressed the most during
lll asynchronous starting operations, namely the starting winding,
~ starting winding parts or the rotor body, or parts of it.
12 1~ Moreover, the automatic starting sequence control device 47
13 ¦ I ensures that a renewed start-up is only possible, if, according
14 I to the contents of the second digital storage 42 (accumulated
15 l, I total value), the temperature-rise condition of the rotor parts
16 Ij affected during start-up is sufficient.
17 j~ Consequently, the high-voltage motor is automatically
18 ~I protected, on the one hand, from overloading during the
19 ll asynchronous start-up, although only the stator current and the
l¦ rotor rotational speed are measured as motor-specific
21 l~ variables. on the other hand, by visualizing the actual and
22 ji the expected temperature-rise condition, as well as the actual
23 ,1 operating condition, an instrument is created for the plant
24 1 I personnel, which permits a flexible plant management, within
11 the bounds of the permissible temperature-rise of the rotor
26 ;~ parts affected during start-up. Thus the number and duration
27 l of shutdowns are considerably reduced, in the case of the
28 ~ high-voltage motor 30, because the execution of start-ups of
29 ll the high-voltage motor 30 is oriented to the rotor parts, which
' are thereby stressed the most.
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i~ 1310~88
1 1¦ In the foregoing specification, the invention has
2 1 ! been described with reference to a specific exemplary
3 11 embodiment thereof. It will, however, be evident that various
4 I modifications and changes may be made thereunto without
I`j departing from the broader spirit and scope of the invention as j
6 ¦j set forth in the appended claims. The specification and
7 ! ¦ drawings are, accordingly, to be regarded in an illustrative
8 ¦I rather than in a restrictive sense.
10 Ij
12
14
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16
17 ¦!`
18 1~ j
19 ~I 1
20 1!
21 1l
22 i1
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24
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l l l
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