Power control of a stalling motor
AssigneeCanadian General Electric Company Limited
InventorsRonald C. Trussler, Stanley V. Reiten, William A. Wyeth
Life of this patent
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Abstract
A control system, for a motor which may be subjected to stalling loads, provides a non-linear increase in motor current during stalling conditions to maintain rated horsepower. When the maximum transient overload current is reached, this current is maintained to keep the motor torque at a maximum until the motor is stalled. This provides maximum motor torque down to a stalled condition and resists stalling. A limit controller determines the maximum time a particular overload motor current can be maintained and when this time has passed the motor current is reduced to rated current. If the motor should stall completely a further reduction in motor current is made automatically.
Claims10
A control system for controlling a motor which may be subjected to stalling conditions, comprising
- a motor having a rated current for continuous operation and a maximum transient overload current limit,
- a controllable source of electrical power connected to said motor,
- reference means for determining a current reference for said motor and providing a first signal representing said current reference,
- sensing means for sensing motor current and providing a second signal representing the sensed current,
- means for receiving said first and second signals and providing a control signal representing their difference,
- control means connected to said power source and responsive to said control signal for determining the output of the source, and
- means for detecting a stalling condition of said motor connected to said reference means for altering said first signal during stalling conditions to require a controlled non-linear increase in motor current over said rated current to maintain motor power at its rated output as motor speed decreases until the motor current reaches said maximum transient overload current and then maintaining said maximum overload current.
A control system for controlling a motor which may be subjected to stalling condition, comprising
- a motor having a rated current and power for continuous operation and a maximum transient overload current limit,
- a generator connected to said motor to supply electrical power thereto,
- excitation means connected to said generator for providing controllable excitation thereto to control the generator output and thereby control the motor,
- a system reference control for receiving a first signal representing a required operation of said motor and providing a second signal derived from said first signal and representing a desired motor voltage,
- a voltage sensor connected to said motor for sensing the voltage across said motor and providing a third signal representing the sensed voltage,
- means receiving said second and third signals and providing a fourth signal representing the difference,
- voltage control and current reference means receiving said fourth signal and providing a fifth signal derived from said fourth signal and representing a desired motor current,
- a current sensor connected to said motor for sensing the motor current and providing a sixth signal representing the sensed current,
- means receiving said fifth and sixth signals and providing a seventh signal representing the difference,
- means responsive to said seventh signal controlling said excitation means in accordance with said seventh signal,
- said voltage control and current reference means providing a linear relationship between said fourth and fifth signals when said motor is operating at less than rated current and providing a non-linear relationship when said motor is operating at more than rated current to maintain rated power as the motor speed decreases until the motor current reaches said maximum transient overload current.
A control system for controlling a motor which may be subjected to stalling conditions, comprising
- a motor having a rated current and rated power for continuous operation at a rated speed and having a maximum transient overload current limit,
- a controllable source of electrical power connected to said motor,
- reference means for determining a desired magnitude of motor current, said reference means including means effective when the motor is subjected to a stalling load and the speed of the motor is consequently decreasing below said rated speed for increasing the desired magnitude of motor current above said rated current as a non-linear function of the difference between the actual motor speed and the rated motor speed until said desired current magnitude reaches said maximum transient overload limit whereupon said desired current magnitude is maintained at said maximum limit, and
- control means responsive to the desired magnitude of current for controlling said power source, said control means being effective during a stalling condition of the motor to cause said power source to provide increasing current to the motor so as to maintain rated motor power as motor speed decreases until the motor current reaches said maximum transient overload current limit and then to provide maximum overload current.
Dependencies are inferred from the claim text.