SECTION - 3
COOLER CONTROL AND
CONTROL CABINET
SECTION - 3.1
LIST OF REFERENCE DRAWINGS
DRAWINGS
1. Diagram of cooler control gear - 34606200054
2. General arrangement of cooler control cabinet - 34606200055
3. Connection diagram of manual drive for off-ckt. tap switch - 44950000241
SECTION - 3.2
CONTROL OF COOLING EQUIPMENT
Drg.: 34606200054 (sht. 01 to 16) - Diagram of cooler control gear
The cooling gear consists of 14 fans and 4 pumps arranged in 2-60% banks. Each 60%
bank consists of 7 fans (5 running and 2 standby) and 2 pumps ( 1 running and 1
standby). Each fan and pump is controlled by their individual contactor and thermal
overload relays.
The system has two supply sources with changeover facility. The fan and pump motor
can be started either from local cooler control cabinet or automatically through W.T.I.
contacts. Each of these mode of operations are described below:
AUTOMATIC SUPPLY CHANGEOVER CIRCUIT:
Auxiliary power supplies from two independent sources of 415 V, 3 phase, 4 wire, 50 Hz
AC supply shall be provided by the purchaser at cooler control cabinet and connected to
the respective terminals as per cooler control schematic drawing. These two incoming
feeders are arranged inside the cooler control cabinet for feeding the supply to power
circuit and control circuit of cooling motor. Electrical interlocking has been provided to
ensure that only one of the two supply feeders is connected to the supply bus wires at a
time. Each supply is provided with a individual fuse switch unit (Q31/Q32). In addition a
supply selector switch (S31) is provided with positions "SUPPLY-A PREFERRED" &
"SUPPLY-B PREFERRED" to choose any one of the two supplies "A" or "B" as
"PREFERRED SUPPLY".
Select "SUPPLY-A" or "SUPPLY-B" as "PREFERRED SOURCE" by means of supply
selector switch (S31). Say "SUPPLY-A" is selected as preferred source. Fuse switch unit
(Q31) of the preferred source is closed first and then the fuse switch unit (Q32) is closed.
Both the fuse switch units (Q31 & Q32) are normally kept closed. Immediately after
closing the fuse switch units (Q31 & Q32), relay (K33 & K34) are energised and in turn
energises respective time delay relay (K51 & K52), by closing a N.O. contact (K33/K34)
in the respective timer circuit. Since SUPPLY-A is selected as preferred source, closing
of the N.O. contact (K33) also energises the main contactor (K31) and "SUPPLY-A" is
thus connected to the supply bus wires. Energisation of contactor (K31) also opens a N.C.
contact in the circuit of contactor (K32) provided for electrical interlocking thus
preventing the alternate SUPPLY-B (Standby) from getting connected to the supply bus
wires at the same time. Another N.C. contact of time delay relay (K51) also opens and
serves as an back up to prevent energisation of contactor (K32).
If the "PREFERRED SUPPLY-A" fail, time delay relay (K51) and main contactor
(K31) gets de energised. The N.C. contact of contactor (K31) instantaneously closes in
the circuit of contactor (K32). N.C. contact of timer (K51) also closes after a set time
delay (5 sec.) thus energising contactor (K32) and standby supply is now connected to
supply bus wires to feed power and control circuit.
As soon as the "PREFERRED SUPPLY-A" revives (comes back to life), the timer (K51)
will energise and will instantaneously open its N.C. contact in the circuit of contactor
(K32) and thus contactor (K32) shall de energise. Subsequently contactor (K31) is
energised and "SUPPLY-A" is again connected to the supply bus wires.
3.2.1.0 MANUAL CONTROL:
For manual control from the cooler control cabinet, cooler control selector "S41" is
selected to "MANUAL" position.
3.2.1.1 CONTROL OF FANS AND PUMPS:
Each of the running fan & pump motor can now be started by energising their individual
contactors (K1..& K21...etc.) by selecting the respective fan & pump control switches
(S1.. & S21....etc.) to "SERVICE" position.
3.2.2.0 AUTOMATIC CONTROL:
For automatic control of fan and pump motors, cooler control selector "S41" is selected
to " AUTO" position.
3.2.2.1 AUTOMATIC CONTROL OF FANS:
The winding temperature indicator contact P1(5,6) closes at preset temperature to
energise auxiliary contactor (K53), which in turn closes its N.O. contact to start all the
running fans selected to "SERVICE" position.
3.2.2.2 AUTOMATIC CONTROL OF PUMPS:
With the further rise in temperature second WTI contact P1(7,8) closes to energise the
auxiliary contactor (K54), which in turn closes its N.O. contact to start pump of bank-A
instantaneously and pump of bank-B with a time delay of 20 seconds selected to
"SERVICE" position.
3.2.2.3 CONTROL OF STANDBY FAN MOTORS:
Any fan motors are selected to "STANDBY" positions by means of fan control switches
S1 to S14. In the event of failure of running fan motor, the auxiliary contactor (K41) &
(K42) gets energised due to closing of N.C. contact of the running fan motor contactor
and closes its N.O. contact K41 & K42 in the standby fan motor contactor circuit to start
the standby fan motors automatically.
3.2.2.4 CONTROL OF STANDBY PUMP MOTORS:
Any pump motors are selected to "STANDBY" positions by means of pump control
switches S21 to S24. In the event of failure of running pump motor, the auxiliary
contactor (K43) and (K44) gets energised due to closing of N.C. contact of the running
pump motor contactor and closes its N.O. contact K43 and K44 in the standby pump
motor contactor circuit to start the standby pump motors automatically.
3.2.3.0 ALARM AND INDICATION CIRCUIT:
3.2.3.1 " FAN ON" INDICATION:
One N.O. contact of each fan motor contactor has been wired upto terminal block to give
" fan on" indication.
3.2.3.2 " PUMP ON " INDICATION:
One N.O. contact of each pump motor contactor has been wired upto terminal block to
give " Pump on" indication.
3.2.3.3 " COOLER CONTROL ON MANUAL/AUTO " INDICATION :
One pole of cooler control selector S41 has been wired upto terminal block to give
"Cooler Control on manual or Cooler Control on auto” indication .
3.2.3.4 "FAN FAIL BANK-A/B " ALARM:
One N.O. contact of each auxiliary contactor K41 & K42 have been wired upto terminal
block to give "fan fail Bank-A/B" alarm.
3.2.3.5 "PUMP FAIL BANK-A/B " ALARM:
One N.C. contact of each contactor(K21 to K24) through a suitable interlock have been
wired upto terminal block to give "Pump fail Bank-A/B" alarm.
3.2.3.6 " 415V AC SUPPLY-A / SUPPLY-B FAIL" ALARM:
N.C. contact of each contactor K51 & K52 have been wired upto terminal block to give
" 415V AC supply-A / supply-B fail" alarm.
3.2.3.7 "CONTROL SUPPLY FAIL" ALARM:
N.C. contact of no volt contactor K35 has been wired upto terminal block to give "control
supply fail" alarm.
3.2.3.8 "415 V AC SUPPLY AUTOCHANGEOVER" ALARM :
N.O. contacts of air break contactors (K31 & K32) through a suitable interlock have been
wired in parallel and terminated upto terminal block to give "415 V AC SUPPLY AUTO
CHANGEOVER" alarm.
3.2.4.0 TRANSFORMER ALARM CONTACTS:
The following transformer alarm initiating contacts are provided and terminated at the
cooler control cabinet:
i) OTI alarm P10(1,2)
ii) WTI alarm P1(1,2)
iii) Buchholz alarm F51(A1,A2)
iv) Low oil level alarm P5(1,2)
v) Oil flow low alarm P11 to P14(1,2)
3.2.4.1 TRANSFORMER TRIP CONTACTS:
1) The following transformer trip initiating contacts are provided and terminated at the
cooler control cabinet:
i) OTI trip P10(3,4)
ii) WTI trip P1(3,4)
iii) Buchholz trip F51(T1,T2)
iv) PRV trip F53 & F54(3,4)
v) Sudden pressure relay trip F52 (1 ,2)
2) The additional safety switch is provided inside manual drive of off-circuit tap switch
as a back up protection to safe guard the transformer in case the operator inadvertently
operates the off circuit tap switch when the transformer is on load. Hand interlock switch
(HIS) contacts 1N.O. & 1N.C. and cam operated switch (84S-2) contacts 1N.O. have
been wired upto terminal block of manual drive of off-ckt. tap switch (refer drg no
449500000241). These contacts are to be wired beyond manual drive in tripping circuit of
the circuit breaker, so that when the handle is inserted and tap switch is operated the
contacts HIS(NO-NO) and 84S-2(NO-NO) closes and trips the circuit breaker.
3.2.5.0 HEATER & ILLUMINATION LAMP CIRCUIT:
A 240 volts, 50 Hz, 1 phase AC supply is fed to the heater and illumination lamp circuit
through a circuit breaker (F36). In the cooler control cabinet four heaters (E1 to E4) have
been provided for preventing moisture condensation and controlled by thermostat switch
(B11). Two fluorescent tubes (E11&E12) have been provided in the cooler control
cabinet and controlled by door switches (S51 to S54). One 240 volts, 1 phase 50 Hz,
A.C. supply 3 pin plug and socket (X55) is also provided in the cooler control cabinet.
SECTION - 3.3
COOLER CONTROL CABINET
Drg. no. : 34606200055 (sht.01 to 04) - General arrangement of cooler control cabinet
The cooler control cabinet is a weather proof steel housing and is floor mounted. The
cabinet is provided with heaters for prevention of moisture condensation.
The following equipments are mounted inside the cooler control cabinet:
A. TEMPERATURE INDICATORS
i) Winding temperature indicator (P1)
ii) Oil temperature indicator (P10)
B. COOLER CONTROL GEAR
All control equipments for supply and cooler control in line with schematic diagram of
cooler control gear drg. no. 34606200055.
C. SUNDRIES
i) Heaters (E1 to E4), heater switch (S36) and
heater circuit breaker (F36)
ii) Thermostat (B11) for controlling heaters (E1 to E4)
iii) Fluorescent tubes (E11 & E12)
iv) Door switches (S51 to S54)
v) Plug & socket (X55)
vi) Terminal block rows (X1 to X5, X7 & X9)
