Winco AS440 - Manual (Page 4)

FITTING AND OPERATING
©2006 4 TD_AS440 AVR_03.09_04_GB
STABILITY ADJUSTMENT
The AVR includes a stability or damping circuit to provide
good steady state and transient performance of the
generator.
A switch is provided to change the response of the
stability circuit to suit different frame size generators and
applications. The table shows the options available.
The slow response settings may prove helpful in
reducing lamp flicker.
The correct setting of the Stability adjustment 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).
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.
The UFRO adjustment is preset and sealed and only
requires the selection of 50/60Hz using the jumper link.
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.
DROOP ADJUSTMENT
Generators intended for parallel operation are fitted with
a quadrature droop C.T. which provides a power factor
dependent 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 analogue input (A1 A2) is provided to connect to a
Power Factor Controller or other devices. It is designed to
accept dc signals up to +/- 5 volts.
WARNING! Any devices connected to this input must
be fully floating and galvanically isolated from ground,
with an insulation capability of 500 Vac. Failure to
observe this could result in equipment damage.
The dc signal applied to this input adds to the AVR sensing
circuit. A1 is connected to the AVR 0 volts. Positive on A2
increases excitation. Negative on A2 decreases excitation.
The TRIM control allows the user to adjust the sensitivity of
the input. With TRIM fully anti-clockwise the externally
applied signal has no effect. Clockwise it has maximum
effect.
Normal setting is fully clockwise when used with a Power
Factor Controller.
OVER EXCITATION (EXC TRIP) ADJUSTMENT
The adjustment is set and sealed in the works and should
not be altered.
An over excitation condition is indicated on the common
LED which also indicates under speed running.
The generator must be stopped to reset an over excitation
condition.
ISOLATING THE EXCITATION CIRCUIT
In some applications it is desirable to isolate the excitation
circuit. There are two different ways of doing this
depending on the AVR connection to the generator stator.
The modifications mentioned below must be done with the
generator at rest.
If the AVR is fitted with a link across the 2 way terminal
block Z2 & 8, then the AVR power circuit is connected to
the main stator winding. In this case a switch with a
Nominal rating of 240vac 10 Amps can be connected
across the AVR terminals Z2 & 8 after removing the link.
When the switch is open, the excitation circuit is
isolated. The link should be kept for future use if required.
If the AVR has a wire connected to terminal Z2 (wire
labeled Z2), then the AVR power circuit is connected to an
auxiliary winding. In this case a switch with a nominal
rating of 240vac 10 Amps can be connected in series with
the wire Z2.
When the switch is open, the excitation circuit is isolated
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