Start/Stop (FS+, FS–)

A contact closure at this input initiates sampling of the synchronizing voltage (to determine phase

rotation) and calculation of the pulse generation time delay. Opening this contact input terminates the

firing pulses.

Terminal Voltage Limiter Enable (VTLIM+, VTLIM–)

The terminal voltage limiter is enabled when contact closure is sensed at this input. When enabled, the

terminal limiter will prevent the generator voltage from exceeding the limiter reference level.

Outputs

The following paragraphs describe the function of the IFM-150 outputs.

Firing Pulses

These outputs supply firing pulses to the gate trigger inputs of the Rectifier Chassis. The firing pulse

terminals used depend on the model of IFM-150. Installation illustrates typical firing pulse output

connections for single-phase and three-phase rectifier chassis applications.

Watchdog Relay (WTCHDG1. WTCHDG2)

The Watchdog Relay output closes to indicate a software execution problem within the IFM-150 or a loss

of power supply. This output remains closed for several seconds after the application of control power.

Alarm Relay (ALRM1. ALRM2)

The Alarm Relay output closes when the monitored synchronizing transformer frequency decreases

below the programmable level of the BESTCOMS Safe Mode Frequency setting. The output opens when

the frequency increases to 1 hertz above the Safe Mode Frequency setting. This output is disabled when

the Start/Stop contact input (FS+, FS–) is open.

Terminal Voltage Limiter Active Relay (LIMACTV1. LIMACTV2)

The normally-open Terminal Voltage Limiter Active Relay output closes when the terminal voltage limiter

activates due to high generator voltage. When the generator voltage decreases below the limiter

reference level, the terminal voltage limiter deactivates and the Terminal Voltage Limiter Active Relay

output opens.