Motor fault detector with optical isolation

Details Motor fault detector with optical isolation Motor fault detector with optical isolation

1987-01-08

1990-12-18

Shoop, Jr., William M.

Electricity: electrical systems and devices

Safety and protection of systems and devices

Motor protective condition responsive circuits

361173, H02H 310

Patent

active

049790692

ABSTRACT:
A motor protection apparatus with a current monitor, the current monitor sensing the presence of current in at least one phase of an electric motor. An ammeter is responsive to the monitor, the ammeter indicating the level of current present in the motor phase. A variable resistor is interposed the monitor and the ammeter, allowing the ammeter to selectively indicate start current and run current present within the motor phase. An optical isolator is responsive to the ammeter for indicating readings of the ammeter at predetermined values. A relay is responsive to the optical isolator, for controlling the presence or absence of input voltage to the motor. The motor protection device senses fault conditions in both the start mode and run mode of the motor, and initiates appropriate responses thereto. The motor is thereby protected from permanent damage by the early detection of fault conditions. The device operates on electric motors having one or more phases, including three phase motors, as well as D.C. motors.

REFERENCES:
patent: 3579217 (1971-05-01), Casey et al.
patent: 3612882 (1971-10-01), Sheppard
patent: 3688157 (1972-08-01), Spears
patent: 3878439 (1975-04-01), Crozier
patent: 4065804 (1977-12-01), Rostad
patent: 4251846 (1981-02-01), Pearson et al.
patent: 4498077 (1985-02-01), Richardson
patent: 4602484 (1986-07-01), Bendikson

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