TP-6862 6/14 61Section 9 Paralleling Generator Sets
2. Passive Control (Used in Droop Paralleling).
The voltage regulators are connected in droop or
cross current compensation. There is no active
control from the controller.
9.2 Paralleling Considerations
9.2.1 Generator Requirements
Alternator and Connections
Units to be paralleled must have the same frequency,
the same number of phases, the same voltage, and the
same phase rotation. The latter merely means that the
voltages across the terminals must reach their
maximum and minimum values in the same order.
Otherwise, the magnetic forces would try to turn the
rotors in opposite directions.
The pitch of the paralleled alternators needs to be the
same or excessive circulating currents may occur.
Motorized Paralleling Circuit Breaker
The Decision-Makerr 3500 controller provides control
of a single motor-operator breaker to selectively close
on or off the bus. For motorized paralleling breakers,
there are two options:
D On the generator set, pre-wired from the factory.
D Remotely mounted. Customer needs to wire to
status, trip, close, charge motor, and bus sensing.
See the wiring diagram in the operation manual for
more information.
Speed Control (Required for Paralleling Done Via
Remote Speed and Voltage Bias Method)
The Decision-Makerr 3500 controller will accept an
input from the paralleling controller. This is the way the
paralleling controller adjusts the frequency and controls
the power output of the generator set.
The Decision-Makerr 3500 controller has the ability to
accept a remote speed adjust input of:
D 0.5 -- 4.5 volts ±5% (values supplied outside of this
range will default the setting to nominal)
Note: Some engines may limit this speed adjust to no
more than approx. +3.5%.
Voltage Regulator
The voltage regulator is integral to the Decision-Makerr
3500 controller and is capable of accepting remote input
for voltage adjustment. It adjusts to:
D 0.5 -- 4.5 volts ±10% (values supplied outside of this
range will default the setting to nominal)
Generator Set Protection
A reverse power relay senses the direction of power
flow. Each generator’s Decision-Makerr 3500
controller contains a reverse power relay. If any unit in
the system has a malfunction such as a loss of fuel
causing current to flow into the generator, the reverse
power relay will sense the reverse power and
disconnect the unit from the system. If reverse power
relays are not used, units still running will drive the unit
that has stopped as a motor.
9.2.2 Paralleling Controller—PGEN
Starting and Stopping Generator Set
The Decision-Makerr 3500 controller has supervisory
control over paralleling. There are several methods that
can be used to start and stop the generator set (consult
the operation manual for more detail):
D CAN gauge
D Modbusr
D Kohler SiteTecht software
D AUTO--RUN/AUTO--OFF button
D RUN button
D Contacts 3 and 4 for remote signal
Frequency and Real (kW) Power
Depending on the state of the paralleling motorized
breaker, the Decision-Makerr 3500 controls the
frequency or kW output of the generator set by sending a
signal to the engine governor over J1939 (CAN).
D Motorized Paralleling Breaker Open. The
generator set speed (frequency) will vary with this
signal. This would be the case while synchronizing.
D Motorized Paralleling Breaker Closed. If the
generator set parallel motorized breaker is closed
and the generator set is operating in parallel with
another power source, this signal will control the kW
load provided by the generator.
Modbusr is a registered trademark of Schneider Electric.
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