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| Illustration 1 | g01332287 |
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Typical Example of a Series Boost Module | |
A series boost module is an option. Series boost allows the self-excited generators to stay on the line (approximately 10 seconds) when there is a short in the generating circuits or in the load circuits.
Therefore, circuit breakers in the load distribution system have the opportunity to trip in sequence. When circuit breakers trip in sequence, there is less chance for a total loss of power of the entire electrical system.
Series boost consists of the series boost module and current transformers (CT).
Voltage sensing and power are applied to the series boost module from the voltage regulator sensing terminals 22 and 24.
When the sensed voltage is within normal limits, an electrical signal is sent to the gate of a triac which is located in the series boost module. This triac short circuits the current transformer. This prevents any series boost during normal operation.
If there is a short circuit in the system that causes the voltage at the regulator sensing terminals to drop to a low value, the control signal to the gate of the triac will be turned off. Current from the current transformer will be rectified. This current will be applied directly to the exciter stator. This field current will be enough to give at least three times full load current into a short circuit. After approximately ten seconds, a timer within the series boost module will again cause a control signal to be applied to the gate of the triac. The triac will short circuit the current transformer. Current flow to the exciter stator will be zero, until the short circuit is corrected.
Note: A PM generator will provide a similar short circuit current characteristic.