Electronic relay to protect motors and thyristors against symmetric overload, phase unbalance and short-circuit
First Claim
1. Electronic relay to protect motors an thyristors against symmetric overload, phase unbalance and short-circuit, of the type that is applied to motors by means of its contacts, producing the automatic disconnection of the motor under certain circumstances and that has a feed source provided with a one-phase transformer, rectifying bridge, filter condenser and regulator that provides a stabilized voltage;
- characterized in that it has some pickups where one-phase signals are generated, connected to some diodes, connected to some capacitors and to a zener diode for the purpose of obtaining rectified, filtered and limited signals, with a voltage level proportional to the line intensity of the protected motor;
including a multiple microswitch which connected to some resistors permits the presetting of said voltage level and nominal triggering intensity of a relay, also including a R-C network that can be timed in various scales comprised of resistors a capacitor and another multiple microswitch that allows adjustment of the triggering time constant and that applied to that voltage level at the non-inverting input of an operational amplifier whose inverting input is at a reference voltage, so that upon the non-inverting input reaching said reference voltage, due to a symmetric overload, the output of the operational amplifier passes to logic state 1, sending a positive signal to gate of a thyristor, which enters into conduction and depolarizes the base of a transistor making it pass from saturation to cut, whereby relay connected to the collector of transistor is triggered, changing the state of its contacts and causing disconnection of the protected motor and lighting up of a LED connected by means of a resistor to the collector of the transistor.
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Accused Products
Abstract
A protective electronic relay is disclosed of the type which includes a feed source with a one-phase transformer, rectifying bridge, filter condenser and voltage regulator. Pickups are provided where one-phase signals are generated, connected to some diodes, connected to some capacitors and to a zener diode for the purpose of obtaining rectified, filtered and limited signals with a voltage level proportional to the line intensity of the protected motor. A multiple microswitch connected to some resistors permits presetting of the voltage level and nominal triggering intensity of a relay. An R-C network that can be timed in various scales comprised of resistors a capacitor and another multiple microswitch allows adjustment of the triggering time constant and is applied to that voltage level at the non-inverting input of an operational amplifier whose inverting input is at a reference voltage. Upon the non-inverting input of the operational amplifier reaching the reference voltage, due to a symmetric overload, the output of the operational amplifier passes to logic state 1. This sends a positive signal to the gate of a thyristor, driving it into conduction and depolarizing the base of a transistor making it pass from saturation to cut-off. As a result a relay connected to the collector of the transistor is triggered, changing the state of its contacts and causing disconnection of the protected motor.
21 Citations
20 Claims
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1. Electronic relay to protect motors an thyristors against symmetric overload, phase unbalance and short-circuit, of the type that is applied to motors by means of its contacts, producing the automatic disconnection of the motor under certain circumstances and that has a feed source provided with a one-phase transformer, rectifying bridge, filter condenser and regulator that provides a stabilized voltage;
- characterized in that it has some pickups where one-phase signals are generated, connected to some diodes, connected to some capacitors and to a zener diode for the purpose of obtaining rectified, filtered and limited signals, with a voltage level proportional to the line intensity of the protected motor;
including a multiple microswitch which connected to some resistors permits the presetting of said voltage level and nominal triggering intensity of a relay, also including a R-C network that can be timed in various scales comprised of resistors a capacitor and another multiple microswitch that allows adjustment of the triggering time constant and that applied to that voltage level at the non-inverting input of an operational amplifier whose inverting input is at a reference voltage, so that upon the non-inverting input reaching said reference voltage, due to a symmetric overload, the output of the operational amplifier passes to logic state 1, sending a positive signal to gate of a thyristor, which enters into conduction and depolarizes the base of a transistor making it pass from saturation to cut, whereby relay connected to the collector of transistor is triggered, changing the state of its contacts and causing disconnection of the protected motor and lighting up of a LED connected by means of a resistor to the collector of the transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
- characterized in that it has some pickups where one-phase signals are generated, connected to some diodes, connected to some capacitors and to a zener diode for the purpose of obtaining rectified, filtered and limited signals, with a voltage level proportional to the line intensity of the protected motor;
Specification