Speed limiting circuit for universal type series or compound electric motor
OwnerTai-Her Yanginventor
Life of this patent
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Abstract
A device for limiting the maximum and/or minimum speed of universal series- or compound-type electric motors. The device includes a first impedance element for limiting the maximum speed of the motor under light load (high speed) conditions to a predetermined value, and a second impedance element for limiting the minimum speed of the motor under high load (low speed) conditions. The limited maximum and minimum speeds of the motor give it operating characteristics which are similar to a shunt motor. Various impedance elements are provided to accommodate
Claims4
A high/low speed limiting circuit for series excitation and compound excitation motors, comprising:
- a low speed limiter shunt device coupled in parallel across a field winding of one of said motors, said shunt device being triggered when a voltage across said field winding exceeds a predetermined first value to shunt current around said field winding to an armature winding of said motor;
- and
- a high speed limiter shunt device coupled in parallel across an armature winding of one of said motors, said shunt device being triggered when a voltage across said armature winding exceeds a predetermined second value to shunt current around said armature winding of said motor;
- whereby when a load applied to said motor causes said field winding voltage to exceed said predetermined first value, said low speed limiter shunt device reduces field current to limit a minimum speed of said motor, and when a substantially no-load condition on said motor causes said armature winding voltage to exceed said predetermined second value, said high speed limiter shunt device maintains field magnetization to limit a maximum speed of said motor.
An adjustable high/low speed limiting circuit for a series excitation motor, comprising:
- a plurality of series-connected zener diodes coupled in parallel across a series-connected field winding and armature of said motor, said diodes having a first plurality of tap leads coupled therebetween;
- a second plurality of tap leads connected at successive intervals along said field winding of said motor;
- and
- a switch device for selectively connecting each first tap leads with a corresponding second tap lead, said switch device being triggered when a voltage across said field winding exceeds a predetermined first value to shunt current around said field winding to an armature winding of said motor, and said switch device being triggered when a voltage across said armature winding exceeds a predetermined second value to shunt current around said armature winding of said motor;
- whereby when a load applied to said motor causes said field winding voltage to exceed said predetermined first value, said switch device reduces field current to limit a minimum speed of said motor, and when a substantially no-load condition on said motor causes said armature winding voltage to exceed said predetermined second value, said switch device maintains field magnetization to limit a maximum speed of said motor.
Dependencies are inferred from the claim text.