Overexcitation Shutdown

Overexcitation detection provides a single-pole solid-state

contact closure across terminals A1 and A2. should the

regulator output voltage exceed 65 Vdc ±2 Vdc for a

sufficient time. For voltage above 105 Vdc ±5 Vdc, there is

a second (shorter) inverse time curve. The total inverse

time delay curve is shown in Figure 2.

After the overexcitation solid-state contact has been

made, the regulator overexcitation circuit can be reset by

decreasing the supply voltage on terminals 3 and 4 to less

than 6 Vac for a minimum of 2 seconds. This may be

accomplished by stopping the prime mover or interrupting

the regulator input by means of a reset switch. In cases

where the generator is operating in parallel mode, it may

not be desirable to allow the regulator alone to shut down

which may cause the generator to be motored. However,

continuous operation at output currents greater than the

continuous rating after the overexcitation contact has been

made may result in failure of the ac supply fuse or may

eventually cause regulator failure. If this kind of operation

will take place, an alternative external means should be

employed to protect the system.

A1 and A2 are optically isolated and floating. Any supply,

12 to 250 Vac or dc may be used, provided that current is

limited to 150 mA. Use of a dc supply to terminals A1 and

A2 will cause the solid-state device to latch after tripping.

In this case, the supply must also be removed to unlatch

the device.