With engine starting controls set on automatic, the generator paralleling switchgear stands by, awaiting a signal from automatic transfer switches to automatically start and synchronize two or more engine-generators when power fails.

Receiving the signal, the switchgear initiates multiple engine-generator start up. The first generator to achieve 90 percent of rated voltage and frequency connects to the emergency bus. Interlocks permit only one generator to connect in the event of simultaneous generator availability. When the first generator connects to the bus, a signal initiates connection of the priority one loads to the emergency bus.

The remaining engine-generators activate their synchronizers in each Digital Generator Paralleling Controller in the switchgear by automatically synchronizing the on-coming generators) with the bus.

When synchronized, the switchgear parallels the on-coming generators) to the bus. Once each generator is added to the bus, the switchgear signals automatic transfer switches to connect the associated priority loads to the emergency bus.

If a generator fails while operating in the automatic mode, the 4000 Series disconnects it from the bus and shuts it down. The switchgear signals the associated priority loads to shed.

The switchgear activates audible and visual alarms to indicate the condition. A control push-button permits operators to over-ride the load shed circuits.

If a bus overloads, causing an under-frequency condition, the switchgear automatically resets the manual override to prevent sustained bus overloading.

When the switchgear is set on load demand operation, it automatically manages the number of generators online, based on total power requirements.

The switchgear compares the actual load of the total generator bus to the running reserve capacity of total generators.

Depending on pre-determined kW set-points and time delays, the switchgear starts, synchronizes and soft loads generators on line. It also takes low priority engine-generators) off-line. It will soft unload the engine, open the circuit breaker and initiate the cool down sequence.

If a bus under frequency or kW overload occurs while engine(s) are cooling down, the running units actively synchronize and parallel to the bus.

If engines are not running, the control system immediately gives the rested engine(s) start signals and parallels them to the bus.

If a bus under frequency or kW overload occurs while generators are on line, the associated loads are shed, the condition is alarmed and a manual reset is required.

When the automatic transfer switches signal that commercial power has been restored and the transfer switches have retransferred loads to the normal source, the switchgear simultaneously opens the generator circuit breakers.

The engines then run for a no-load, user-defined cool-down period. The control system stands poised for the next power failure or regular system test.