Electricity: electrical systems and devices – Safety and protection of systems and devices – Motor protective condition responsive circuits
Patent
1977-03-07
1979-04-24
Moose, Jr., Harry E.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Motor protective condition responsive circuits
361 92, H02H 709
Patent
active
041515757
ABSTRACT:
An electrical device is connected to the magnetic starter of an electrical motor to protect the motor windings from a loss of power on one or more input lines of a three phase power source. The device includes two transformers each being connected across two input lines and having one input line in common with each other. The transformer secondaries are each connected in a relay circuit so that a voltage on the secondary of each transformer above a predetermined value will actuate the relay in its respective circuit. The contacts of both relays are connected in series with each other and with the magnetic starter of the electrical motor so as to actuate the magnetic starter when both relays are closed. When the voltage on any of the three input lines drops substantially below a normal operating level, one or both of these relays will open, immediately turning off the magnetic starter and shutting down the motor to prevent damage to the motor windings. The transformer primary windings are connected through a terminal strip to the power source to enable series or parallel connections to accommodate both 240 volt and 480 volt power lines.
REFERENCES:
patent: 1809827 (1931-06-01), Bower
patent: 3413535 (1968-11-01), Hubby
patent: 3711747 (1973-01-01), Sahara et al.
patent: 4060841 (1977-11-01), Allen
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