MAGNETIC CIRCUIT OPENING AND CLOSING MOTOR STARTING SWITCH IN RESPONSE TO HEAT VARYING MACNETIC PERMEANCE

• US 3,566,225 A
• Filed: 09/26/1968
• Issued: 02/23/1971
• Est. Priority Date: 10/07/1967
• Status: Expired due to Term

• Current Assignee: Poulsen Erik Kurt
• Original Assignee: Poulsen Erik Kurt
• Inventors: POULSEN ERIK KURT
• Application Number:
  US04/762,757
• Time in Patent Office: 880 Days
• US Class Current: 318/792
• CPC Class Codes: H02K 17/30 Structural association of asynchronous induction motors with auxiliary electric devices influencing the characteristics of the motor or controlling the motor, e.g. with impedances or switches
• CPC Class Codes: H02P 1/42 for starting an individual single-phase induction motor H02P27/04 takes precedence

Abstract

A synchronous motor and a starting circuit therefore in which a switch in series with the motor winding determines the starting period during which the starting winding is electrically energized. The switch has a leaf-spring movable contact tending toward opening the starting circuit kept in a circuit-closing position by a magnetic system which has a ferromagnetic member therein rendered nonmagnetic by heat applied by a PTC-resistor in series with the motor starting winding so that the ferromagnetic member releases a magnet on the movable contact closing the switch and the motor starting period is thus determined.

Claims

1. A starting circuit for a single-phase asynchronous motor having a main winding and a starting winding, said starting circuit comprising means for electrically energizing said starting winding and said main winding, a switch in series with said starting winding for keeping said starting circuit closed and said starting winding in circuit during a predetermined starting period and subsequently opening said starting circuit to electrically disconnect said starting winding upon completion of said starting period, a movable contact on said switch, a magnetic system comprising a permanent magnet releasably closing said switCh mounted on said movable contact, said movable contact being magnetically actuated by said magnet to a switch-closing position and automatically operable to a switch-opening position when magnetic system attraction of said magnet is reduced sufficiently to allow said contact to open said switch, a stationary magnetizable member cooperating with said magnet to define a magnetic circuit for causing said magnet to close said switch, and means to reduce the permeance of said magnetizable member thereby to reduce magnetic attraction by said magnetic system to cause said magnet to effect release of said movable contact and determine said starting period.

2. A starting circuit for a single-phase asynchronous motor according to claim 1, in which said magnetizable member comprises a ferrite.

3. A starting circuit for a single-phase asynchronous motor according to claim 1, in which said means to reduce the permeance of said member comprises means electrically energized heating said member.

4. A starting circuit for a single-phase asynchronous motor according to claim 3, in which said means electrically energized comprise a positive temperature coefficient resistor in series with said main winding and in parallel with the starting winding heating said member above the Curie point thereof.