Automatic revolution rate limit monitor for prime movers - has fail-safe circuit for checking pulse integral counter resetting

摘要

The method of automatically monitoring a revolution rate limit for many types of machine, esp. prime movers, involves a digital pulse transducer and a device measuring the time between successive rotation pulses. The circuit involved, is proof against component failure giving very accurate and reliable monitoring. All conceivable component failures tending to block the limit value signal are automatically detected and signalled or cause the unit to assume a safe condition. This is achieved by converting short circuits into open circuits using breakers and open circuits into disconnect signals using quiescent current signals. The absence of count pulses or the incorrect condition of a counter also cause disconnect signals. An alarm signal is generated if the counter is not reset to zero by the time measurement. The alarm is suppressed if the fault condition occurs simultaneously in redundant channels under critical conditions.