Modular oscillator for parallel operation - uses pulse width modulated tower transistor modules with power control, synchronisation, and isolation to allow redundant operation

摘要

The modular oscillator allows parallel operation of oscillators without the master/slave arrangement, thus giving a truly redundant system. The oscillator modules are 1kVA pulse width modulated transistor bridge output types, switched at 20kHz to give a smooth 50Hz sine wave output. Each oscillator has a contractor (13) in its output line and includes current, voltage, and frequency feedback control to ensure even load sharing. A synchronisation circuit provides the input signals to the frequency control circuit in each oscillator module. A 25.6kHz quartz crystal controlled clock provides the timing for all oscillator modules. Faulty modules are detected by over - or under - voltage output, by detection of power inflow rather than outflow, and by overcurrent detection. When a fault is detected the supervisory circuit operates the contactor in the output of the faulty module, isolating it from the oscillator output.