A device for measuring energy delivered by a motor to a load is adapted to be connected to the motor which is coupled to the load and connected to a power source through first and second power supply lines. The device includes a line voltage sensing circuit for sensing the voltage across the power supply lines, a line current sensing circuit for sensing the current flowing through the motor and a pulse width modulator which modulates the sensed voltage to produce a pulse width modulated first electrical signal. The device also includes a first switch, responsive to the pulse width modulated first electrical signal which modulates an output of the line current sensing circuit to produce a power waveform and an integrator which integrates the power waveform to produce an output signal indicative of the energy delivered by the motor to the load. The device further includes a switch controller which compares the output signal to a first reference signal to detect the existence of an overload condition and which compares the output signal to a second reference signal to detect the existence of an underload condition. The switch controller opens a second switch to disconnect the motor from the power source in response to either an overload condition or an underload condition.

Electronic motor load sensing device

An apparatus and method for controlling a motor used for rotating a drill stem is disclosed. Silicon control rectifier based system regulates the power to the motor. A control unit coupled to the SCR regulator and the motor monitors the motor input current, voltage and speed levels. If during operation the motor current exceeds a predetermined value and at the same time the motor voltage or speed falls below a predetermined value, the control unit activates an alarm condition and causes the SCR regulator to controllably ramp down the current supply to the motor and then reduces the motor speed reference.

Apparatus and method for controlling a motor

Control circuit system wherein low level signals are delivered through small (miniature) gauge control conductors to remote control circuit breakers to control connection of load devices to load bus through use of solid state circuitry. Such control may be used between the flight station of an aircraft and the various load centers remote therefrom, in an automobile or in an industrial or utility system. The circuitry is also responsive to faults in the load circuits, and current limiting warning lights (CLWL's) located in the power supply of the control conductors may limit current and indicate the status of faults in the control and/or remote power circuits. A large number of CLWL's for the different circuits may be arranged in a matrix at a control station and means with corresponding load identifying indicia are provided to facilitate changes and correlation of lighted CLWL's with respect to the controlled load switching device. The load switching devices may be associated in a plurality of priority groups and means provided to disconnect all the devices in a group simultaneously either manually or sequentially in reverse order of group priority upon increasing power system failures or in response to other control logic.

Electric power system control utilizing low level signals and miniature gage wiring

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.

Alternating current motor protection system

A circuit for supplying a progressively increasing amount of power to a plural phase motor during rotor acceleration employs a relaxation oscillator to vary the effective conduction angle for each applied line voltage phase. Circuitry is provided to restore an oscillator timing capacitor to a reference condition at a like point during each power phase cycle such that each phase supplies essentially the same monotonically increasing motor accelerating energy. In accordance with varying aspects of the present invention, overload and undervoltage protective circuits remove power from the motor responsive to abnormal operating conditions.

P Zanini

Papers

Motor control circuit