Load protection circuit
First Claim
1. A load protector for disconnecting an electrical load from electrical power lines in the event of power line voltage abnormality comprising:
- input terminal means adapted for connection to electrical power lines;
load terminal means adapted for connection to said load;
fault detector means coupled to said input terminal means for producing a voltage-abnormality-indicating condition responsively to the presence of a power line voltage having an amplitude beyond a given value and for producing a normal-voltage-indicating condition responsively to the presence of a power line voltage having an amplitude not beyond said given value;
control switching means operable to a first state supplying electrical power from said input terminal means to said load terminal means and operable to a second state interrupting said supplying of electrical power from said input terminal means to said load terminal means, said control switching means further including means responsive to said fault detector means for actuating said control switching means to said second state responsively to the presence of said voltage-abnormality-indicating condition and to said first state responsively to the presence of said normal-voltage-indicating condition;
power supply means for supplying electrical operating power to said control switching means and said fault detector means, said power supply means including means for continuously providing said operating power from electrical power delivered to said load terminal means in said first state and a timing secondary power supply means powered from electrical power delivered to said input terminal means for providing said operating power from electrical power delivered to said input terminals in said second state and at periodic intervals only and including means for preventing actuation of said control switching means to said first state thereof except during said periodic intervals.
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Accused Products
Abstract
A battery operated standby inverter power supply uses an electromechanical relay switching network to connect and disconnect line power between input and output terminals. An overcurrent relay pulser rapidly opens the switching system relay contacts upon transition to battery mode, and a breakover diode network accelerates field collapse in the relay coil attendant to reversion of the relay to its normally closed condition attendant to each battery to line transition. A fault detector establishes acceptable line voltage thresholds, the exceeding of either of which triggers operation from line to battery mode. These triggering thresholds are automatically pulled closer together during initial system startup. During system startup and attendant to each battery-to-line transition, the fault detector is momentarily latched to indicate acceptable line voltage conditions, thereby removing its susceptibility to transient retriggering. During start-up mode a low-current transformerless power supply connected to the power line input terminals charges a storage capacitor sufficiently to power the fault detector through a single interrogation cycle, to actuate the switching circuitry to line mode operation if proper line voltage conditions are sensed. Collapse of this capacitor voltage during this operation terminates the interrogation cycle, a new cycle begins when the capacitor has been suitably charged. An overload detector senses the load current in line mode and prevents actuation to battery mode if the load connected to the power supply output exceeds the rated current value of the inverter.
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Citations
10 Claims
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1. A load protector for disconnecting an electrical load from electrical power lines in the event of power line voltage abnormality comprising:
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input terminal means adapted for connection to electrical power lines; load terminal means adapted for connection to said load; fault detector means coupled to said input terminal means for producing a voltage-abnormality-indicating condition responsively to the presence of a power line voltage having an amplitude beyond a given value and for producing a normal-voltage-indicating condition responsively to the presence of a power line voltage having an amplitude not beyond said given value; control switching means operable to a first state supplying electrical power from said input terminal means to said load terminal means and operable to a second state interrupting said supplying of electrical power from said input terminal means to said load terminal means, said control switching means further including means responsive to said fault detector means for actuating said control switching means to said second state responsively to the presence of said voltage-abnormality-indicating condition and to said first state responsively to the presence of said normal-voltage-indicating condition; power supply means for supplying electrical operating power to said control switching means and said fault detector means, said power supply means including means for continuously providing said operating power from electrical power delivered to said load terminal means in said first state and a timing secondary power supply means powered from electrical power delivered to said input terminal means for providing said operating power from electrical power delivered to said input terminals in said second state and at periodic intervals only and including means for preventing actuation of said control switching means to said first state thereof except during said periodic intervals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification