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Description of operation and hardware
What this chapter contains
This chapter describes the operation of a synchronization application, shows a
connection diagram and presents the RSYC unit.
Intended use of the RSYC unit
A drive equipped with the RSYC unit is designed for applications in which a large
fixed-speed motor must be started to a weak supply line. Drive starts the motor
smoothly (no high starting current as with the direct on line start) simultaneously
generating a high torque. When the nominal speed (frequency) is reached, RSYC
unit verifies the status of the supply line and the drive output and controls the
switch-over contactors that shift the connection of motor from the drive to supply
line.
Operation
The RSYC unit monitors two voltage signals, one measured from the supply line
and other from the drive output. The signals indicate the phase shift and frequency.
The unit output signal (BUFOUT, 0 ...10 V) indicates the synchronization status for
the drive. When the BUFOUT signal reaches 5 volts, the supply line and the drive
output voltages are synchronic, i.e. the phasing and frequency are the same.
The drive control program constantly corrects the drive frequency reference (set to
50 Hz) on basis of the BUFOUT signal by using the Trim function. When the
synchronizing conditions are reached, i.e. the drive output and the supply line
phasing's match and the frequencies are equal:
BUFOUT signal reaches 5 volts indicating "synchronic" status for the drive
•
application program.
RSYC unit gives a control pulse for the contactor control circuitry.
•
Drive control logic switches the inverter modulation (IGBT control pulses) off.
•
Contactor control circuit opens contactor K1, disconnecting the motor from drive.
•
Contactor control circuit closes contactor K2, connecting the motor to the supply
•
line.
Description of operation and hardware
9
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