Winco AS480 - Manual (Page 4)

© Cummins 2008 4 TD_AS480 AVR_04.08_02_GB
ADJUSTMENT OF AVR CONTROLS
VOLTAGE ADJUSTMENT
The generator output voltage is set at the factory but can
be altered by adjustment of the VOLTS control on the AVR
board or by the external hand trimmer if fitted. Before
adjusting the generator output voltage , note the following
warnings.
WARNING! Do not increase the voltage above the
rated generator voltage shown on the rating plate
mounted on the generator case.
WARNING! Do not ground any of the external hand
trimmer terminals. Failure to observe this could cause
equipment damage.
To adjust the generator output voltage, proceed as follows:
1. Before running the generator set, turn the [VOLTS]
control fully anti-clockwise. Turn the [STABILITY] control
to its midway position and the external hand trimmer (if
fitted) to its midway position.
2. Connect a suitable voltmeter (0-300Vac) across Line
and Neutral of the generator.
3. Start the generator set, and run on no load at nominal
frequency e.g. 50Hz (or 60Hz).
4. If the red Light Emitting Diode (LED) is illuminated, refer
to the section on Under-Frequency-Roll-Off adjustment.
5. Carefully turn the [VOLTS] control clockwise until the
required voltage is reached.
6. If instability is present at rated voltage, refer to the
section on Stability adjustment.7. Voltage adjustment is
now completed.
STABILITY ADJUSTMENT
The AVR includes an optimised stability circuit to provide
good steady state and transient performance of the
generator. Links are provided to change the response of
the stability circuit to suit different frame size generators
and applications. A slow response setting is more
appropriate on small generator sets and will 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 position for the
control is slightly clockwise from this point (i.e. where the
machine volts are stable but close to the unstable region).
UNDER-FREQUENCY-ROLL-OFF ADJUSTMENT:
(UFRO)
The AVR incorporates an under-speed protection
circuit which produces a volts/Hz characteristic when
the generator frequency falls below a preset threshold
- known as the "knee" point. The red Light Emitting
Diode (LED) gives indication that the UFRO circuit is
operating in the low frequency region.
The UFRO adjustment is preset and sealed and only
requires the selection of 50Hz or 60Hz operation
using the jumper link.
For normal operation, the LED should illuminate as
the frequency falls just below 95% of nominal.
i.e. 47Hz on 50Hz systems or 57Hz on 60Hz systems.
DROOP ADJUSTMENT
Generators intended for parallel operation should be
fitted with a quadrature droop C.T. The C.T. is
connected to S1, S2 on the AVR and provides a
power factor dependent signal for the AVR voltage
sensing circuit. This allows the control of generator
reactive current when two or more generators are
operated in parallel.
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 amount of
voltage droop. With the control fully anti-clockwise
there is no droop.
OVER EXCITATION TRIP
The over-excitation trip level is set at the works at
65Vdc and cannot be altered. An over excitation
condition is indicated on the LED (which also indicates
under speed running).
The over-excitation is allowed to exist for
approximately eight seconds to prevent nuisance
tripping and to support normal transients and short-
term overloads. The generator voltage falls to low
levels when the trip is activated. The generator must
be stopped to reset an over-excitation shutdown
condition.
EXCITATION BOOST SYSTEM
There are no user adjustments on the EBS
module just connect the unit and it is ready for
use.