Automatic transfer control device and frequency monitor

Details Automatic transfer control device and frequency monitor Automatic transfer control device and frequency monitor

1976-07-19

1978-05-16

Schaefer, Robert K.

Electrical transmission or interconnection systems

Plural supply circuits or sources

Connecting or disconnecting

307 64, 307 80, 307 81, H02J 100, H02J 300

Patent

active

040900908

ABSTRACT:
An automatic transfer control device for generating signals to cause associated circuit interrupters to selectively energize an electrical distribution system from either of a pair of electrical power sources. The device includes an over- and under-frequency monitoring circuit to determine if the power source frequency is within preset limits. The frequency monitoring circuit includes a zero-crossing detector which activates a clock oscillator, the output pulses of which are accumulated by a counter for one half cycle. The number of pulses occurring during the half cycle is compared with a limit value stored in a read-only memory. An alarm signal is activated if the number of pulses accumulated is out of limits. The address inputs of the read-only memory are connected to the alarm signal generator and to a flip-flop toggled by the zero-crossing detector so that any of four limit values are selectively accessed for input to the comparator: high limit, low limit, return-to-normal after high alarm, and return-to-normal after low alarm. A strobe circuit is provided to only momentarily energize the read-only memory, thereby reducing power consumption.

REFERENCES:
patent: 3337742 (1967-08-01), Baehr et al.
patent: 3529215 (1970-09-01), Xavier et al.
patent: 3748533 (1973-07-01), South
patent: 3990007 (1976-11-01), Hohhof
patent: 3993984 (1976-11-01), Penrod

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