Water pump protector

• US 4,420,787 A
• Filed: 12/03/1981
• Issued: 12/13/1983
• Est. Priority Date: 12/03/1981
• Status: Expired due to Term

• Current Assignee: Spring Valley Associates, Inc.
• Original Assignee: Spring Valley Associates, Inc.
• Inventors: Tibbits, John L., Springer, Lamar D., Sellers, John W. Jr.
• Primary Examiner(s): EISENZOPF, REINHARD
• Application Number:
  US06/327,269
• Time in Patent Office: 740 Days
• Field of Search: 361/79, 361/85, 361/30, 417/45, 318/455, 318/474, 318/479, 318/805, 318/806
• US Class Current: 361/79
• CPC Class Codes: H02H 7/0827 responsive to underload or no-load, e.g. pump-off control circuits for pump motors

Abstract

A water pump protector which includes electrical circuitry through which an electric motor is energized. The electric motor operates a water pump. The circuitry senses the phase angle between the voltage and the current applied to the electric motor. When the phase angle indicates that the motor is operating without a load, the circuitry deenergizes the electric motor. Thus, the water pump is protected against damage which may occur when the water pump is operated without pumping water.

Claims

1. Protective circuitry for a liquid pump which is operated by an electric motor which is connected to a source of alternating current energy through a pair of electric conductors and switch means, comprising:

voltage divider means joined to the electric conductors,

a first operational amplifier, the first operational amplifier having a pair of input terminals and an output terminal,

means joining the input terminals of the first operational amplifier to the voltage divider means to provide a voltage representing the voltage between the electric conductors and in phase therewith,

a second operational amplifier, the second operational amplifier having a pair of input terminals and an output terminal,

means joining the input terminals of the second operational amplifier to at least one of the electric conductors to provide voltage representing the current flow through the electric conductor and in phase with the current flow through the electric conductor,

an exclusive-OR-gate provided with a pair of input terminals and an output terminal,

means joining the output terminals of the operational amplifiers to the input terminals of the exclusive-OR-gate,

a third operational amplifier, the third operational amplifier being provided with a pair of input terminals and an output terminal,

means joining the output terminal of the exclusive-OR-gate to one of the input terminals of the third operational amplifier,

means joining the other input terminal of the third operational amplifier to one of the electric conductors,

a fourth operational amplifier, the fourth operational amplifier having a pair of input terminals and an output terminal,

means joining the output terminal of the third operational amplifier to one of the input terminals of the fourth operational amplifier, and means joining said one input terminal of the fourth operational amplifier to the output terminal thereof,

means joining the other input terminal of the fourth operational amplifier to a source of direct current voltage,

a transistor provided with a base, a collector and an emitter,

means joining the output terminal of the fourth operational amplifier to the base of the transistor,

an electrical actuator member for operation of the switch means,

means joining the collector of the transistor to the electrical actuator member,

means joining the emitter of the transistor to a source of direct current voltage,

the first and second operational amplifiers providing representative voltages to the exclusive-OR-gate in accordance with the voltage applied to the electric conductors and the current through said one conductor, the exclusive-OR-gate detecting the time sequence between said voltage at the output terminal of the first operational amplifier with respect to the voltage at the output terminal of the second operational amplifier, the exclusive-OR-gate emitting an average output voltage in accordance with the total time period that both of the operational amplifiers are emitting a voltage, the third operational amplifier emitting an output voltage when the average output voltage of the exclusive-OR-gate exceeds a given magnitude, the fourth operational amplifier emitting an output current to the base of the transistor when the output voltage of the third operational amplifier exceeds a given magnitude, the transistor emitting a current sufficient to energize the electric actuator member, the electric actuator member thus operating the switch means to deenergize the electric motor to protect the pump which is operated by the electric motor.

2. The protective circuitry of claim 1 in which the means joining the output terminal of the exclusive-OR-gate to the third operational amplifier includes electrical filter means.

3. The protective circuitry of claim 1 in which the means joining said other input terminal of the third operational amplifier to one of the electric conductors includes means for generating a variable reference voltage.

4. The protective circuitry of claim 1 in which the means joining the input terminals of the second operational amplifier to at least one of the electric conductors includes resistance means.

5. A protective circuit for a liquid pump which is operated by an electric motor comprising:

alternating circuit electric circuit means for connection to a source of electrical energy and for energization of the electric motor,

sensing means for deenergization of the electric motor including first sensing means sensing the alternating current voltage applied to the electric circuit means and providing a constant direct current voltage during each half cycle that the voltage applied to the electric circuit means has a given potential, second sensing means sensing the alternating current flow in the electric circuit means and providing a constant direct current voltage during each half cycle that alternating current flow is in a given direction,

phase detector means,

means joining the first and second sensing means to the phase detector means, the phase detector means providing a direct current voltage output during the time that both the first sensing means and the second sensing means produce a direct current voltage,

voltage level detector means,

means joining the voltage level detector means to the phase detector means and to the alternating current electric circuit means and providing a direct current potential during the time that the average direct current voltage output of the phase detector means exceeds a potential applied to the voltage level detector means from the electric circuit means,

and connection means joining the voltage level detector means to the means for deenergization of the electric motor for deenergization of the electric motor when the average current voltage output of the phase detector means provides a direct current potential in excess of a given magnitude.

6. The protective circuit of claim 5 in which the connection means includes latch means providing a substantially constant current output after energization thereof and amplifier means for amplifying the output current of the latch means for flow of current to the means for deenergization of the electric motor.