General Electric Canada, Inc.

General Electric Company

James H Dymond

Raymond K J Ong

Raymond David Findlay

Gerald Burt Kliman

Robert Henry Rehder

John M Young

Bernard John Moore

Dale Derr

Nick N Saidi

James Victor Kay

A method for shorting rotor windings in a wound rotor induction machine is disclosed. The method includes the steps of monitoring rotor current for a frequency indicative of a desired steady-state operating condition and electronically shorting the rotor windings when the monitored rotor current frequency reaches a defined threshold indicative of the desired steady-state operating condition.

Electronic shorting of wound rotor windings

Rogowski coil method of determination of bearing lubrication in dynamoelectric machines

Some dynamoelectric machines develop shaft E.M.F.'s during operation which lead to circulation currents in the shaft of the machine. The shaft current will attempt to flow through the bearings of the machine, unless some action is taken to prevent or limit said current flow. This invention minimizes the circulation of rotor shaft currents by providing a return path for the shaft current through an insulated conductor located in the center of the shaft of the machine. The insulated conductor is electrically attached to the shaft at the ends of the conductor. The conductor may extend the length of the shaft.

Minimizing shaft currents in dynamoelectric machines

Rotor temperature in induction motors is estimated without the need for any direct temperature sensors, by using only computer calculations based on data readily available in the motor control center. Thus for any given motor, it is generally possible to predetermine a relationship between rotor temperature and rotor resistance, so that by determining rotor resistance, rotor temperature can be calculated. Rotor resistance, in turn, can be calculated from measured information relating motor slip and motor torque. Any of several methods can be employed for determining torque and slip. Temperature estimation can be obtained by use of equivalent circuit methods, and additional relationships can be obtained from a simplified equivalent circuit.

Sensorless estimation of rotor temperature in induction motors

A rotor for an induction motor of the squirrel cage type wherein the rotor bars are exposed to a resilient anti-sparking compound in the rotor slots of the machine. The rotor bars are provided with a longitudinal slot to permit the insertion of the anti-sparking compound after assembly of the squirrel cage rotor. Alternatively, the laminations may be shaped to produce a longitudinal groove in the rotor bar slot to permit the insertion of the anti-sparking compound in the groove so produced. Of course, both the rotor bar and the rotor slot may both be provided with complimentary slots adjacent one another in which the anti-sparking compound may be injected.

Spark suppression of induction type rotors of dynamoelectric machines

A dynamoelectric machine has a stator with a stator core and a plurality of spaced apart radially extending ventilation ducts. A rotor mounted for rotation within the stator has a shaft with a plurality of salient poles. Each salient pole has a winding on it and each pole with its winding constitutes a pole member. Adjacent pole members define between them an interpolar space. Cooling air enters each interpolar space from each end when the machine is operating, moves generally axially as portions of the air change direction to move radially outwards through the air gap separating the rotor and stator and then through the ventilation ducts. The air flow, in a radial outward direction, tends to be less at the ends of the rotor and through the ventilation ducts adjacent the ends of the stator. The invention places a baffle at each end of each interpolar space. The baffle is in a generally radial plane and has an outward edge adjacent the outer limit of the interpolar space as defined by the tips of the poles, and an inward edge spaced from the bottom of the interpolar space. The baffle improves the air flow radially outwards adjacent the ends of the rotor and the stator.

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Peterborough, Canada

James H Dymond