FIELD OF INVENTION
The invention relates to a method of cooling for two unrelated heat sources through
integration of three different fluids flowing in separate circuits.
BACKGROUND OF THE INVENTION & PRIOR ARTS
BHEL, Bhopal is a leading manufacturer of Large & Medium size rotating
electrical machines for Power, Industrial and other specialized applications. BHEL also
manufactures inverters and control panels for controlled supply and operation of these
machines. These machines and controllers are supplied together as integrated unit for
some typical applications. Both machines and controllers are potential heat sources and
have to be provided with cooling arrangements to take away the generated heat to
achieve designed performance. Various types of cooling arrangement such as air to air,
air to water etc. are utilized for this purpose. The source of generation of the cooling
fluids may also vary on case to case basis.
The controllers and machines in general are provided with separate cooling
arrangement, which do not have any connection with each other. However many a times,
due to system and space constraints and to save on number of components and energy,
an integrated cooling may be used for both heat sources. One such scheme is presented
through this patent which combines cooling of a rotating machine and the controller
where three different fluids integrated in a single cooling unit have been utilized.

As per the background art research, the system presented here has never
been utilized earlier anywhere. The innovation presented here is system specific and has
evolved from the particular constraints experienced at the time of proposing solution for
desired system of a machine operated through controller for a specific application.
OBJECTS OF THE INVENTION
The prime object of the invention is to develop an integrated scheme of
cooling two unrelated heat sources utilizing three separate fluids.
Another object of the invention is to introduce associated control system to
check the operation of the complicated cooling system for its smooth running.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows the boundary condition of system.
Figure 2 shows the schematic flow diagram.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
1) Heat generating sources

The system consists of mainly two heat sources both of which require coolers for
their successful operation.
a) Machine : The Permanent Magnet synchronous machine (HX-1004) is a IP23,
horizontal machine with a forced ventilation unit at its non-drive end to supply
sufficient air for cooling the heat generated due to losses taking place in
rotating machine. The hot air after passing through machine goes out from
drive end into an air to water cooler (HX-1002). The water available for cooling
in air to water cooler is from sea water pipeline. The hot air after getting cooled
in air-water cooler is brought back to ambient temperature and released into
surrounding atmosphere.
b) Controller : The IGBT based controller gives control supply and operative
signals to machine. The IGBT stack (HX-1001) has to be cooled with help of
demineralized water as normal water is not suitable for this purpose. The
demineralized water is in limited quantity and can not be replaced very easily.
Therefore it is required that the limited quantity of DM water used for the
purpose has to be recirculated after cooling through sea water pipeline which
is also being used to cool the hot air of the machine as stated in (a) above.
2) Fluids for cooling the system
This section explains the availability of various fluids for cooling the above stated
heat generating sources.

a) Sea water is abundantly available through seawater inlet pump (004) at 20 deg
C. The sea water can be used to cool the equipment and then the hot sea water
can be discharged back to sea.
b) The forced ventilation unit (005) mounted on the machine supplies air at
ambient temperature for cooling of machine components.
c) Demineralized water in limited quantity is available from separate source (006),
which can be recirculated, for cooling of the IGBT stack (HX-1001).
3) Coolers
This section explains the coolers which have been used for making the integrated
cooling scheme for machine and controller.
a) Air-water cooler (A/W) (001)
This is double circuit cooler with sea water in tubes and hot air from machine
around the tubes. The sea water in tubes cools the hot air.
b) Water to water cooler (W/W) (002)
This is another double circuit cooler with demineralized water in the tubes and
sea water from another circuit, around them. The sea water cools the hot
demineralized water coming from IGBT stack
4) Expansion tank with level gauge (003)
An expansion tank (003) has been provided in the DM water circuit to take care of
the increase in volume of water after getting heated from IGBT stack. Also
expansion tank acts as refilling source for demineralized water.

5) Interconnected Piping And Associated Acceossories
Piping, bends, reducers, flanges, gaskets, bolting, valves, and pressure
instrumentation are in accordance with the engineering practice and standards.
6) Boundary conditions
This section explains the various boundary conditions in which the system had to
be designed.
a) The machine is air cooled.
b) The LCP is DM water cooled which is limited in quantity and has to be
recirculated
c) Sea water at 45 bar is available in unlimited quantity which can be used to cool
both the hot air from machine and DM water from LCP.
d) The sea water should not mix with DM water circuit as saline water will damage
the LCP stack.
e) The sea water pressure of 45 bar is not allowed to be transmitted to DM water
line as the LCP stack is not suitable for such high pressure.
7) The complete system
The complete system comprising of the components as outlined above is depicted
in the line diagram-1 and the 3D model of diagram-2.
The FV unit throws air over motor components and this air after getting hot, flows
through shell side of the A/W cooler where it gets cooled through sea water flowing

through tubes. The cooled air is discharged back to atmosphere at the same
temperature at which it entered the machine.
The sea water enters the tubes of the A/W cooler and cools the hot air from
machine. After cooling hot air from machine, sea water enters the tubes of W/W
cooler for cooling the DM water flowing over the tubes. After exiting from W/W
cooler the hot sea water is discharged back to sea.
The DM water flows in a closed circuit with help of a motor-pump unit. The DM
water takes away the heat generated in the LCP stack and gets cooled through
sea water.
8) Control Circuitry
Various control measures have been provided to meet the requirements of the
system.
a) A salinity meter is provided in the closed DM water circuit. Whenever there is
possibility of mixing of sea water with DM water due to some leakage
developing in the tubes of W/W cooler, the salinity meter senses the salinity of
the DM water circuit and gives audio visual alarm after the set value of salinity
in DM water circuit is exceeded.
b) A pressure transmitter has been provided in the DM water circuit which senses
the increase in pressure of the DM water line and after a set value operates
the solenoid valves provided before and after W/W cooler to isolate the DM
water line from the system. Thus any increase of pressure in the DM water line
due to leakage of W/W cooler tubes can be avoided.

c) A differential pressure gauge is provided across the motor-pump unit which
measures difference of pressure across two ends of motor-pump to take care
of any irregularity in supply of DM water pipeline so that motor-pump unit can
be tripped instantly.
9) Typical Operating Parameters Of The System
One set of typical values for the complete system as described above are given
below. The values can be verified from standard engineering calculations of
thermal transfer and pressure drop etc.
a) Sea water inlet temperature to A/W cooler – 30 deg C
b) Sea water temperature at outlet of A/W cooler – 35.43 deg C
c) Sea water maximum pressure – 45 bar
d) LPM of sea water – 66 LPM
e) Air temperature at inlet to RPM – 35 deg C
f) Air temperature at inlet to A/W cooler – 60 deg C
g) Air flow rate through A/W cooler – 60 m3/min.
h) Loss dissipated through A/W cooler – 25 kW
i) Sea water inlet temperature to W/W cooler – 35.43 deg C
j) Sea water temperature at outlet of W/W cooler – 39.1 deg C
k) DM water temperature at inlet to LCP stack – 47 deg C
l) DM water temperature at outlet of LCP stack – 43.1 deg C
m) LPM of DM water – 50 LPM
n) Loss dissipated through W/W cooler – 17 kW

WE CLAIM
1. A method of cooling two different heat sources, namely, synchronous machine (HX-
1004) and IGBT Stack (HX-1001) for the controller, using three different cooling
media, namely; air, sea water and demineralized water comprising;
- forced ventilation unit (005) for supplying air at ambient temperature;
- sea water inlet pump (004) for supplying sea water at 20oC;
- separate demineralized water source (006) supplying DM water;
wherein, the sea water cools first the hot air from machine in A/W cooler and
afterwards cools demineralized water (DM) in (W/W) cooler before being
discharged back to sea.
2. A system to implement the method of claim 1, wherein air to water (AW) cooler
(001), water to water (WW) cooler (002), expansion tank (003) are configured along
with piping, bends, reducers, flanges, gaskets, bolting, valves and instrumentation
to maintain boundary conditions as synchronous machine (HX-1004) is air cooled;
IGBT stack (HX-1001) is demineralized water (DM) cooled;
sea water at 45 bar used to cool both hot air from synchronous machine (HX-1004)
and DM water from IGBT stack (HX-1001)
wherein double circuit line for Air to water (A/W) cooler and water to water (W/W)
cooler do not allow sea water to mix with DM water from IGBT stack (HX-1001) and
hot air from synchronous machine (HX-1004).

3. The method as claimed in claim 1, wherein control of the whole system is provided
through:
- salinity meter in closed DM water circuit to indicate mixing of sea water with DM
water giving an audio visual alarm in case it exceeds the set limit;
- pressure transmitter in DM water circuit to sense increase in pressure of DM
water, operating solenoid valve to isolate DM water line from the system
- differential pressure gauge across motor-pump unit to measure pressure
difference across two ends to check any irregularity in supply of DM water pipeline
and tripping the motor-pump unit.