Basler Electric PRS-250 Veri-Sync Relay

The CBS 212A Current Boost System assists Basler SSR-series voltage

regulators during generator overload conditions and supplies the exciter

field during generator short-circuits. When used with three wire or 4-wire

generators, the CBS 212A supports sustained single-phase and multiple

-phase, line-to-line faults.

In addition, the CBS 212A permits four-wire generators to support A-phase

and B-phase line-to neutral faults.

The CBS 212A assembly consists of a Current Boost Module and two

current transformers (CTs). The Current Boost Module is designed for

behind-the-panel mounting.

An Operating Point Adjustment control and Operating Point Indication LED

are located on the front panel of the Current Boost Module.

An Output Limit Adjustment control is located on the bottom panel of the

Current Boost Module.

Special power CTs connect to two phases of the generator output and

provide current to the Current Boost Module. The Installation chapter

provides details about CT selection.

Current Boost Module

The Current Boost Module rectifies the ac current received from the CTs

and provides dc current boost to the generator exciter field.

During normal generator operation, power from the generator output

provides sufficient exciter field power and the CBS 212A remains dormant.

During normal operation, the CTs are effectively shorted by the internal

SCRs of the CBS 212A. Normal generator operation is indicated by the

Operating Point Indication LED being lit.

If the generator output voltage decreases below the operating-point setting,

the CBS 212A detects the voltage drop, turns off the Operating Point Indication

LED, and removes the SCR “short-circuit” from the CTs.

The CBS 212A then provides full current boost to the generator exciter until

the voltage returns to a level just above the operating point setting.

The Controls and Indicators and Installation chapters provide information

about setting the Operating Point Adjustment.

An adjustable voltage limiting circuit prevents the Current Boost Module

output from exceeding the specified percentage of the nominal output

voltage (60. 120. or 220 Vdc). The Output Limit Select Jumpers are used

to select the nominal output voltage (60. 120. or 220 Vdc) and the Output

Limit Adjustment is used to set the desired percentage of the nominal output

voltage. The Output Limit Adjustment is adjustable over a range of 50 to

100 percent of the jumper-selected nominal output voltage.