US 5,149,998 AGranted

Eddy current drive dynamic braking system for heat reduction

AssigneeEaton Corporation

InventorJohn H. Wolcott

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Abstract

A dynamic braking means for a variable speed dynamoelectric eddy current drive consists of an ac motor (4) rotationally coupled through a shaft (6) to an inductor drum assembly (13) of an eddy current coupling (3), where an annular field coil 12 generates an electromagnetic field which couples the inductor drum assembly to a pole assembly (10) which is rotationally coupled to an output shaft (16) which drives an inertial load (20). Upon command to stop and brake, a controller (30) signals a motor switch (26) to disconnect the ac motor from the ac source and connect it to a dc source, causing a braking torque to be produced. Concurrently, the controller signals a coupling switch (28) to go to an open position momentarily until the motor decelerates to approximately zero speed, whereupon the coupling switch is again closed, coupling the inertial load to the motor, thereby providing a braking action. The major portion of dissipated kinetic energy is thus shifted from motor to coupler, which has a higher heat capacity.

Claims8

Dependent claims

A dynamoelectric machine braking system for reduced drive motor heating comprising:

a dc power source for supplying dc electrical power;
an ac power source for supplying ac electrical power;
an ac electric drive motor having a motor output shaft and a motor coil electrically connected to said ac power source;
an eddy current coupling comprising, a rotor member rotatable about an axis of rotation, an inductor means drivingly attached to said motor output shaft and rotatable about said axis of rotation relative to said rotor member, a coupling coil means connected to said ac power source for producing an electromagnetic field thereby electromagnetically coupling said rotor member and said inductor means, an output shaft having a first end connected to said rotor member and a second end connectable to an inertial load whose motion is to be braked;
motor switch means for connecting said motor to said ac power source and for connecting said motor to said dc power source;
and
control means for controlling the state of said motor switch means and for directing said ac power source to said coupling coil means when the amplitude of said ac power source directed to said coupling coil means is reduced to substantially zero thereby decoupling said rotor member from said inductor drum and when said control means directs said motor switch means to connect said motor coil to said dc power source until the rotational speed of said motor is substantially reduced in value, and wherein said control means increases the amplitude of said ac power source to said coil means to electromagnetically recouple said rotor member to said inductor drum thereby effectuating a braking action on said inertial load while dissipating an increased quantity of heat in said eddy current coupling.

4 more elements

Dependencies are inferred from the claim text.