STABILITY ADJUSTMENT
The AVR includes a stability or damping circuit to provide
good steady state and transient performance of the generator.
The correct setting can be found by running the generator at
no load and slowly turning the stability control anti-clockwise
until the generator voltage starts to become unstable.
The optimum or critically damped position is slightly clockwise
from this point (i.e. where the machine volts are stable but
close to the unstable region).
FREQUENCY SELECTION
The "jumper" selection lead should be correctly linked for the
nominal operating frequency of the generator (see diagram).
UNDER FREQUENCY ROLL OFF (UFRO) ADJUSTMENT
The AVR incorporates an underspeed protection circuit which
gives a volts/Hz characteristic when the generator speed falls
below a presettable threshold known as the "knee" point.
The red Light Emitting Diode (LED) gives indication that the
UFRO circuit is operating, and turning the UFRO control
clockwise lowers the frequency setting of the "knee" point and
extinguishes the LED.
For optimum setting, the LED should illuminate as the
frequency falls just below nominal, i.e. 47Hz on a 50Hz
system or 57Hz on a 60Hz system.
If the red LED is illuminated and no output voltage is present,
refer to Over Voltage protection adjustment.
DIP ADJUSTMENT
The 'DIP' adjustment allows some control over the generator
voltage dip upon the application of load.
This feature is mostly used when the generator is coupled to
turbo-charged engines with limited block load acceptance,
and operates only when the speed is below the UFRO knee
point.
The circuit works by increasing the volts/Hz slope to give
greater voltage roll off in proportion to speed.
With the 'DIP' control fully anti-clockwise the generator
voltage characteristics will follow the normal V/Hz line as the
frequency falls below nominal.
Turning the 'DIP' control more clockwise provides greater
voltage dip allowing easier engine recovery.
DROOP ADJUSTMENT
Generators intended for parallel operation are fitted with a
quadrature droop C.T. which provides a power factor
correction signal for the AVR. The C.T. is connected to S1, S2
on the AVR.
The DROOP adjustment is normally preset in the works to
give 5% voltage droop at full load zero power factor.
Clockwise increases the amount of C.T. signal injected into
the AVR and increases the droop with lagging power factor
(cos Ø).
With the control fully anti-clockwise there is no droop.
TRIM ADJUSTMENT
An auxiliary input is provided to connect to the Power Factor
controller. It is designed to accept dc signals up to +/- 5 volts.
The dc signal on this input (A1,A2) adds to or subtracts from
the AVR sensing circuit, depending on polarity.
The Trim control allows the user to adjust the sensitivity of the
AVR to the PF controller output.
With Trim fully anti-clockwise the PF controller has no effect.
Clockwise it has maximum effect. Normal setting is fully
clockwise.
OVER VOLTAGE (OVER V) ADJUSTMENT
A miniature circuit breaker is supplied for this feature. It may
be fitted in the generator or supplied loose for fitting in the
control panel.
The AVR includes over voltage protection circuitry to remove
generator excitation in the event of a short circuit power
device or loss of sensing input.
Separate terminals are provided for the over voltage circuit
E1, E0 which connect to the generator windings
independently of the AVR sensing terminals. (Typical E1, E0
voltage = 240 Vac).
Provision is made for the connection of the circuit breaker to
break terminals K1, K2, interrupting the power supply to the
exciter field. The addition of this circuit breaker (and leads B0
and B1) causes the AVR power supply to be interrupted
automatically in the event of an over voltage.
The OVER V adjustment is normally set and sealed at the
factory but can be reset on retrofit AVRs. Clockwise increases
the tripping voltage.
When the circuit breaker is supplied loose,
the AVR is fitted with a link on terminals
K1-K2 to enable operation of the AVR.
When connecting the circuit breaker this
link must be removed.
In the event of operation of the circuit breaker, indicated by
loss of generator output voltage, manual resetting is required.
When in the "tripped" state the circuit breaker switch lever
shows "OFF". To reset move the switch lever to the position
showing "ON".
When fitted in the generator, access to the breaker is gained
by removal of the AVR access cover.
Terminals which are live with the
generating set running are exposed when
the AVR access cover is removed.
Resetting of the circuit breaker must be
carried out with the generating set
stationary, and engine starting circuits
disabled.
The circuit breaker is mounted on the AVR mounting bracket
either to the left or to the right of the AVR depending upon
AVR position. After resetting the circuit breaker replace the
AVR access cover before restarting the generating set.
Should resetting of the circuit breaker not restore the
generator to normal operation, refer to the Service section in
the generator Instruction Manual.
Caution !
TD_SX421.GB_09.02_01
PO Box 17 • Barnack Road • Stamford • Lincolnshire • PE9 2NB
Tel: 00 44 (0)1780 484000 • Fax: 00 44 (0)1780 484100
Website: www.newage-avkseg.com
© 2002 Newage International Limited.
Reprinted with permission of N.I. only.
Printed in England.
