2301A 9907-018 WOODWARD

This section describes the general theory of operation of the two versions of the 

SPM-A Synchronizer. Figure 1-1 shows the SPM-A Synchronizer with voltage 

matching. Figure 1-2 shows a typical synchronizer system block diagram. Figure 

1-3 shows a functional block diagram of the synchronizer. 

Synchronizer Inputs 

The SPM-A Synchronizer checks the phase angle and frequency of the bus and 

an off-line generator which is to be paralleled. The voltage inputs from the bus 

and generator are first applied to separate signal conditioner circuits. Each signal 

conditioner is a filter which changes the shape of the voltage input signals so 

they can be accurately measured. A phase offset potentiometer in the signal 

conditioner circuit is adjusted to compensate for phase errors. (This adjustment is 

factory set with identical bus and generator inputs. It should be readjusted only 

where a phase offset has been caused through the line transformers of the 

installation.) The signal conditioners also amplify the bus and generator signals 

and apply them to the phase detector. 

Operating Modes 

A user-installed mode switch (single-pole, four-position) controls the relay driver. 

The switch must be wired to synchronizer contacts 10 through 13 (see the plant 

wiring drawing). The four positions are OFF, RUN, CHECK, and PERMISSIVE. 

When the switch is OFF, the synchronizer is out of operation. 

The RUN mode allows normal synchronizer operation and breaker closure 

signals. The speed bias circuit continues to operate to maintain synchronization 

for one second to allow time for the breaker closure signal. When one second 

has elapsed, the lockout circuit activates to disable the synchronizer. The lockout 

circuit is reset automatically when the relative phase angle exceeds the window 

limit after the generator is disconnected from the bus. 

The CHECK mode allows normal synchronizing and voltage matching, but does 

not permit a breaker closure signal.