131, 8th Main, 3rd Phase

Peenya Industrial Area

BANGALORE-560 058
Ph: 080-28393703, 41170448
Fax: 080-41170447
E-mail: sanelecblr@airtelmail.in
 INDEX
1) GENERAL INFORMATION
2) TECHINICAL SPECIFICATION
3) FEATURE PROVIDED
4) INTERCONNECTION DIAGRAM
5) OPERATION
6) PARALLELOPERATION AMG GENERATORS
7) STATIC TEST PROCEDURE
8) TROUBLE SHOOTING CHART
VOLTAGE REGULATOR
MODEL: SES-12
GENERAL INFORMATION
This AVR is a compact, medium power Full wave
rectified AVR designed to give excellent performance
with both LT & HT generators upto 10MVA.
This AVR is capable of building up the voltage
with a very low residual voltage say from 1.5V to 2V
AC at power input terminals.
This AVR has built in settable protective
features for under speed and over excitation.
TECHNICAL SPECIFICATION
 POWER INPUT
VOLTAGE : 240 V AC
FREQUENCY : 50/60Hz
BURDEN : 2.5kVA

 SENSING INPUT
VOLTAGE : 110V AC, 3Ø
FREQUENCY : 50/60Hz
BURDEN : 5VA
 OUTPUT
DC VOLTS : Max 200 V DC
DC AMPS : 15AMPS DC(Max)

 DROOP : 10% max. for 5A/1A

(derived through line CT)
from ‘Y’ Ph.

 VOLTAGE : ± 0.5% at Regulator

REGULATION sensing terminals.

 VOLTAGE DRIFT : <± 1% for 40ºC change in

ambient.
 UNDER SPEED : Settable between 40 Hz to
PROTECTION(FRO) 55Hz.

 BUILD-UP (at power : 1.5V AC (typical)

input terminals) 2.5V AC (guaranteed)

 VOLTAGE VARIATION: ± 10% (Typ) with 10K pot.

 RESPONSE : Response time abt 70ms

 RECOVERY : Closed loop voltage
recovery at m/c terminals
betw 0.5 to 2 sec
depending on size of ACG.
 ACCESSORY INPUT : ± 4.5V DC will change
terminal voltage by ± 15%
(approx.). The accessory
input must be isolate.

 EXCITATION CURRENT: Inverse Time delayed settable

LIMIT betw 2A to 12A.

 TEMP. OPERATION : -20ºC to +60ºC

 FEATURES PROVIDED
The main Features are as follows:

1) V-Trim : Voltage Adjustment

2) FRO : Frequency Roll off
3) STAB : Oscillation control
4) O-Exc : Over Excitation Limit
5) ACC : Accessory Input
6) QDC : Droop
V-TRIM: Using this pot, voltage can be adjusted within
± 10% of rated voltage. Clockwise increases
the setting and anti-clockwise decrease the
setting.
FRO : Using this pot, we can set the frequency at
which the voltage starts dropping. Clockwise
decreases the setting and anti-clockwise
increases the setting.
STAB : Using this pot, we can control the oscillation.
Clockwise leads the voltage stable and
anticlockwise leads the voltage to oscillation. Too
many clockwise will leads to more damping.
O-Exc : Using this pot we can fix the band of
excitation current at which the voltage starts
dropping. Clockwise increases the setting
and anti-clockwise decreases the setting.
ACC : Set to change the terminal voltage by ±15%
for ± 4.5VDC input.
QDC : Set to produce 4% droop(16V) for 5Amps
input current from ’V’ phase.
INTERCONNECTION DIAGRAM
 OPERATION
After connecting the AVR as per the Interconnection
diagram and after attaining the machine at full speed,
Switch ‘ON’ the AVR and voltage will build-up upto rated
voltage.
Note:
Before switching ‘ON’ the AVR keep V-Trim pot in middle
position.
Droop CT to be shorted for Solo operation.
 After voltage build-up trim the voltage using V-
Trim pot upto the rated voltage. Adjust the stability pot
provided inside the unit to get good response and recovery
time i.e., turn STAB pot anticlockwise till voltage starts
hunting and again turn clockwise till voltage stops hunting.
From this point turn slightly more clockwise to avoid
hunting on load and load removal.
Check all the parameters at No-Load conditions and
when found O.K. load the machine upto rated kVA. Check
all the parameters at Full Load condition.
 PARALLEL OPERATION
AMONG GENERATORS
During parallel operation the generator sets active &
reactive loads according to the droop characteristics in the
prime mover. So, it is required to share the loads in
proportion to their individual ratings.
 ALTERNATOR kVAR
SHARING
Just as equality of droop characteristics decides KW
sharing in engine (governors), equality of KVAR sharing is
decided by voltage droops provided.
 PARALLEL OPERATION
1. PRE PARALLEL OPERATION
2. PARALLEL PROCEDURE.
3. PARALLELING PROBLEMS.
4. PARALLEL OPERATION
THROUGH ACCESSORY INPUT.
1. PRE PARALLEL OPERATION
 It is essential that the paralleling droop signal from the CT
bears proper phase relationship with respect to the sensing
input.
 Verify that 110V sensing is derived across U & V Phases
only through (PT) or directly (415V) and the droop CT
installed in W Phase only.
 The droop CT should be in excess of 5VA rating and wound
for CL 1.0 accuracy.

 The variable droop resistor or potentiometer mounted

inside the AVR is set to give about 4% droop for 5A input or
1A input.
 Before attempting to parallel operate 2 or more gensets it
is recommended that the following tests be performed:
1. Run the set on no load and adjust the voltage to normal
rated value.
2. Verify that the paralleling CT secondary is not shorted.
3. Apply 25% to 100% load to the set at UNITY PF. The
generator output should change less than +/-1%.
4. If the generator output changes more than 1% check the
paralleling CT connection and the phase in which it is
installed.
5. Apply 25% to 100% load at 0.8pf. Voltage should drop from
4 to 6% with rated load. If the voltage rises instead of
drooping reverse the CT sensing leads.
During the above tests verify that the voltage and the
speed do not drift or oscillate erratically.
 PARALLEL PROCEDURE
The oncoming generator voltage phase sequence must be the
same as that of the bus to which it is to be paralleled.
1. Adjust the voltage of the oncoming generator (the
generator to be paralleled) to match the bus voltage.
2. Adjust the oncoming prime mover speed so that its
frequency is slightly faster than the load bus.
3. Observing the Synchroscope, close the oncoming
generator circuit breaker when the generator is in phase
with that of the bus ( slightly less than 12 ‘O’ clock
position of synchroscope allowing for circuit breaker
closure time).
4. Immediately after closing the breaker, observe the line ammeter.
It should be well within the rated current reading. If not
immediately reopen the circuit breaker and completely review
the connections.
5. If operation is normal after paralleling adjust prime mover speed
control so that the generator takes no load, thereby avoiding
the possibility of the reverse power relay tripping the
generator from the bus.
6. Adjust voltage & speed so that the generator is taking its
share of KW & KVAR.
7. If, two or more generators using the same type AVRs are on a
common bus vary the bus load and make voltage, speed and
parallel droop compensation adjustments as necessary to
obtain the most optimum sharing.
 PARALLELING PROBLEMS
 If after paralleling with the bus, improper operation results,
try first to determine which control system is faulty the
voltage or the speed control.
 A high ammeter reading or circuit breakers opening may
occur in either case. Immediately after closing the on
coming generator circuit breaker observe KVAR & KW
readings.
 A large KVAR reading (positive or negative) indicates
faulty voltage regulating system.
 An unbalanced KW reading may indicate a faulty speed
regulating system.
 By and large, all paralleling problems are caused by
incorrect system interconnections
 If the KVAR drifts upward upon paralleling then the
CT is not in circuit or connected reverse.
 If KVAR drifts downwards when the machine is
paralleled to the bus (KW varied from 0 to 100%) by
more than 10%, the paralleling CT is in wrong
phase.
 PARALLEL OPERATION
THROUGH ACCESSORY INPUT
 Applying a DC voltage of ±4.5V at the Accessory input will
vary the terminal voltage approximately by 15%.
 The Accessory input to the regulator must be wired with
the Autosynchroniser/PLC controls in such a way as to
result stable operation.
Before parallel operation, the accessory input could be used
for voltage matching purposes and after parallel operation
for sharing or balancing KVARs. It is important to take care
of the polarity of accessory input such that the desired
result is achieved. Reverse polarity condition will lead to
runaway conditions.
 The accessory input should always be used in
conjunction with the droop circuit. The droop circuit
ensures proper stability of parallel operation while the
accessory input maintains the desired KVARs on a closed
loop basis.
 STATIC TEST PROCEDURE
1) Connect the AVR as shown in the diagram.
2) Ensure that the variac is in minimum position.
3) Switch ‘ON’ the 415V, 3phase supply to the variac.
4) Keep V-Trim pot in minimum position.
5) Switch ‘ON’ the AVR switch and slowly vary the variac.
6) The lamp starts glowing slowly, further increase the
voltage till it co-incides the set value and the lamp goes off.
7) Turn V-Trim pot fully clockwise again the lamp will glow
slowly.
8) Increase the voltage through variac, the lamp should
remain ‘ON’.
8) Measure the voltage at terminals 1 and 2 and keep the
voltage at 110V.
9) Turn FRO pot provided in the PCB anticlockwise
slowly then the lamp should go off and turning
clockwise the lamp should again glow.
10) It is difficult to see stability effect in static test, so
it has to be carried out only in closed looped.

If the unit behaves as above said procedure

then the unit is said to be healthy.