Note: Descriptions are shown in the official language in which they were submitted.
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- 1 - Case 2747
IIQUID COOLING SYSTEM_FOR ELECTRICAL APPARATUS
This invention relates to a liquid c~oling
system for electrical apparatus and in paxti~ular it
relates to an improved system for preventing or
minimizin~ problems involving leakage and including a
syqtem mOnitGr-
Apparatus is well known for liquid cooling ofthyristors or diodes. The following patents, referred
to by way oE example only, are representative:
Canadian Patent NoO 732,688 - COLALACO - issued
April 19, 1966; Canadian Patent Mo. 931,626 - BEASLEY
et al - issued August 7, 1973; Canadian Patent No.
950,96~ - NYFFELER et al - issued July 9, 1974; United
States Patent ~o. 4,178,630 - OLSSON issued
December llv 1979.
All the patents referred to above describe
apparatus or systems for removing heat from arrays of
thyristors, diodes, or similar semiconducting
devices. They do not particularly direct the~selves
to leakage of the cooling liquid, the occ~rrence of
air locks in the circulating system, or cavitation.
The leakage of the cooling liquid in high voltage,
high current converters or similar equipment could be
disastrous, causing damage to the semiconducting
devices and system failure. Air locks can affect the
efficiency of cooling, and while not likely to cause
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damage as abruptly as a leak, can damage the
semiconducting devices. Cavitation can also affect
the cooling efficiency~
The present invention prevents or reduces
damage by leakage, air locks or cavitation and
provides a monitor system which activates an alarm
when conditions of cooling are affected.
It is therefore a feature of this invention
to provide an improved system for the liquid cooling
of semiconductive devices.
It is a further feature of the invention to
provide an improved liquid cooling system for
semiconductive devices which provide an alarm or
shutdown with unacceptable conditions in the system.
Accordingly there is provided a liquid
cooling system for semiconductor apparatus comprising,
a reservoir for containing a cooling liquid, a lower
header communicating with said reservoir at a lower
portion thereof, an upper header communicating with
said reservoir at an upper portion thereof, said lower
header sloping upwardly in a direction away from said
reservoir, and said upper header sloping upwardly in a
direction towards said reservoir to reduce the
occurrence of vapour locks, a plurality of arms
exterlding between and communicating with said lower
and upper headers and having means for conducting heat
from said semiconductor apparatus, a liquid pump for
circulating cooling liquid from said reservoir through
said lower header, said arms, and said upper header to
said reservoir, and a vacuum pump connected with said
rPservoir above the level of cooling liquid therein to
reduce the pressure in sai.d reservoir, said headers
and said arms, whereby any leaks will result in air
entering rather than liquid escaping~
The invention will be described with
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reference to the single figure schematic diagram
showing a sectional view of a cooling system according
to the invention.
Referring to the drawing, a reservoir 10
which includes a heat exchanger 11 is connected with a
lower header 12 and an upper header 14. Arms 15
interconnect ~he lower and upper headers 12 and 14~
These arms 15 are in heat conducting engagement with
or in some form of cooling arrangement with electrical
apparatus (not shown3 which is the source of heat.
The electrical apparatus could be semiconducting
devices. A dielectric cooling liquid 16 fills the
lower header 12, the arms 15, the upper header 14 and
the reservoir 10 towards the tGp as shown. A pump 17
circulates the cooling liquid in the direction
indicated by arrows 18 and 18A.
The lower header 12 is sloped upwardly in a
direction away from reservoir 10, and the upper header
~; 14 is sloped upwardly towards reservoir 10. This is
to prevent air locks which could affect the cooling.
- The slope shown in the dra~ing is exaggerated for ease
of illustrationO It should be reali~ed that it is
acceptable to have the headers perfectly level, that
is with zero slope, and no air locks would occur. The
important thing is that there should not be any
portion sloping in the opposite direction to that
shown, and this can be achieved using level headers.
In other words, the headers can slope in the
directions shown over a range of zero degrees to
whatever the design will convenientl~ accommodate~ As
a precaution against errors shifting during
construction or assembly, it is preferred to have a
slight slope on the headers in the dir~ction shown.
; The heat exchanger 11 has an inlet 20 and an
outlet 21 which are connected to a source of water and
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a waste or disposal for the water, respectively ~not
shown).
A sigh-t glass 22 is connected to the wall of
reservoir 10 to display the level of the cooling
liquid~ A level sensor 23 is connected by a conductor
24 to a monitor 25~ The monitor 25 gives an alarm or
shuts the equipment down, as desired, if the level
sensed is beyond predetermined limitsO
; A vacuum pump 26 i 5 connected to the top of
reservoir 10 above the level of the cooling liquid in
the system. Preferably a check valve 27 is connected
between the pump 26 and reservoir 10 to maintain a
reduced pressure in the reservoir should a fault
develop in the pump or when the pump is not running.
The vacuum pump 26 provides a reduced pressure in the
system so that small leaks do not result in the escape
of the cooling liquid, but rather permit the entry of
air. As was previously mentioned, the eacape of
liquids could be quite damaging in apparatus using
large semiconductoxs.
The presence of a leak will permit air to be
drawn into the system and this will call for increased
running of the vacuum pump. A conductor 28 connects
the vacuum pump 26 with monitor 25 and carries a
signal representing the running time of vacuum pump
26r Monitor 25 monitors the running time and if it
exceeds a predetermined level (prolonged running
indicates a leak) then monitor 25 triggers an alarm or
shuts down the system, or both.
A sight glass 30 is connected with reservoir
10 and the level of liquid in sight glass 30 indicates
the degree or amount of reduced pressure. A level
sensor 31 is mounted adjacent sight glass 30 and is
connected to monitor 25 by a conductor 32. If the
level departs from a predetermined level, indicating a
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leak, then monitor 25 triggers an alarm or shuts down
the system.
A level sensor 33 may, if desired, be mounted
adjacent sight glass 30 to sense the level of liquid
indicati~g a large 105s of vacuuril, that is indicating
a large increase in pressure. Sensor 33 is connected
by a conductor 34 to monitor 25. If the level rises
in sight glass 30 to level sensor 33 indicating an
abrupt loss of vacuum, then monitor 25 triggers an
alarm or shuts down the system. It will be apparent
that sight glass 30 could be replaced by other
pressure indicating devices which can trigger an alarm
at a preset level.
In summary, the monitor gives an alarm or
shuts down the system when a leak is indicated by
increased running time of the vacuum pump, an abrupt
loss of vacuum or departure from a normal liquid
level. Outward leakage of liquid is prevented except
in unusual circumstances by the reduced pressure, and
the design including sloping passageways avoids air
locks and reduces cavitation.
In another form of the invention thexe is no
requirement for vacuum pumps 26. It is necessary to
provide a reduced pressure or a negative pressure only
~5 in the circulating &ystem, that is in the lower and
upper headers 12 and 14 and in arms 15. This is the
region where outward leakage of liquid is dangerous.
The reservoir need not have a reduced or negative
pressure in it~ If a circulating pump 17 is used
which has sufficient capacity, it can provide the
required reduced pressure in the circulating system.
For example, a circulating pump 17 may have a drop
across it which is of the order of 7 psi. The
reservoir 11 may be assumed to be at atmospheric
pressure, or a relative standard or zero pressure.
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The upper header 14 on the other side of the pump 17
would have a reduced pressure of 7 psi compared to the
reservoir. l'his reduced pressure of 7 psi would rise
in the circulating system at points upstream until it
becomes zero again at the reservoirO This has been
found to be adequate and is a less expensive
arrangement. The sight glass 30 or equivalent
pressure gauge would, of course, have to be moved from
the reservoir 11 where it is shown in the drawings to
a point in the circulating system, for example in
header 14.
It is believed the operation of the equipment
will be understood from the preceding description.
