Alternating current motor protection system
AssigneeCarrier Corporation
InventorVirgil E. Eisenhauer
Life of this patent
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Abstract
A system for protecting a three-phase motor is disclosed. The system includes a signal conditioning circuit which senses the magnitude of current flowing through each motor phase and generates a single-line, three-phase voltage output signal having each of its phases corresponding to a single motor current phase. This three-phase voltage output signal is efficiently utilized by a microcomputer system to detect motor current overload and motor current imbalance. The microcomputer system instructs a motor controller to shut down the motor in response to a motor current overload or motor current imbalance.
Claims7
A system for protecting a three-phase alternating current motor from current overload and from current imbalance comprising:
- means for sensing the current magnitude of each phase of the alternating current supplied to the motor;
- signal conditioning means for generating a three-phase electrical output signal in response to the current magnitudes sensed by the current sensing means, the magnitude of the first, second and third phase of said output signal being proportional to the magnitude of the first, second and third phase, respectively, of the alternating current;
- signal processing means for monitoring the magnitude of each phase of the output signal to determine the absolute magnitude of each phase of the alternating current and to determine the relative magnitude of each phase of the alternating current relative to the magnitude of each of the other phases of the alternating current;
- and
- means for terminating the operation of the motor when the absolute magnitude of a current phase exceeds a preselected value or when the relative magnitude of a current phase exceeds a preselected value.
Dependencies are inferred from the claim text.