EP0223599A2 - Relais thermique à action retardée avec bimétal double - Google Patents

Relais thermique à action retardée avec bimétal double Download PDF

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Publication number
EP0223599A2
EP0223599A2 EP86309014A EP86309014A EP0223599A2 EP 0223599 A2 EP0223599 A2 EP 0223599A2 EP 86309014 A EP86309014 A EP 86309014A EP 86309014 A EP86309014 A EP 86309014A EP 0223599 A2 EP0223599 A2 EP 0223599A2
Authority
EP
European Patent Office
Prior art keywords
bimetallic
thermal relay
strips
delayed action
action thermal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP86309014A
Other languages
German (de)
English (en)
Inventor
Ciro Calenda
Giuseppe Notaro
Fabrizio Rotulo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Texas Instruments Inc
Original Assignee
Texas Instruments Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Texas Instruments Inc filed Critical Texas Instruments Inc
Publication of EP0223599A2 publication Critical patent/EP0223599A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H61/00—Electrothermal relays
    • H01H61/002—Structural combination of a time delay electrothermal relay with an electrothermal protective relay, e.g. a start relay
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H5/00—Snap-action arrangements, i.e. in which during a single opening operation or a single closing operation energy is first stored and then released to produce or assist the contact movement
    • H01H5/02—Energy stored by the attraction or repulsion of magnetic parts
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/02—Details
    • H01H37/64—Contacts
    • H01H37/66—Magnetic reinforcement of contact pressure; Magnet causing snap action

Definitions

  • the present invention relates to a bimetallic relay, with normally closed contacts, particularly suitable for use as a starting relay for single-phase induction motors, of the kind used in compressors for refrigerators and the like. More particularly the invention concerns a fast release relay, with double bimetal, relatively insensitive to the variations of ambient temperature.
  • a single-phase induction or asynchronous motor requires special devices for overcoming the obstacle of starting, especially under load, in order then to go into normal running operation. That problem of starting has been resolved with various devices, one of which provides the use of a supplementary winding, more particularly called a starting winding, which is deenergized or excluded from use in the motor after the motor is started. To obtain this result, one uses a relay connected in series with the starting winding with normally closed contacts which open after a certain delay.
  • delayed relays or delay relays generally coming under two basic types: - electromechanical or gravity relays; and - thermal relays with PTC (positive temperature coefficient) resistive heaters.
  • the general object of the present invention is to make a relay which has the advantages of both above-mentioned types but without having their respective limitations. Besides the fact of being able to have the normally closed contacts, so as to make possible their use with motors of the PSC (Permanent Start Capacitor) type, the other characteristics to be realized in the relay of the present invention are the following: - low energy consumption; - maximum independence of the operating characteristics from variations of the ambient temperature; - reasonably short reset times; - high reliability, in the range of millions of cycles; - resistance to vibrations; - small number of parts, all of fully established technologies, to hold down the manufacturing costs; and - guarantee of reliable operation in any position independent of gravity.
  • PSC Personal Start Capacitor
  • a delayed action thermal relay comprising a housing molded of plastic material with a first, a second, and a third electrical terminal already inserted and preferably molded into the plastic housing material, a first U-shaped bimetallic strip extending between the first and third electric terminal and carrying in an intermediate position at the base of the U-shape a contact element, and another contact element which is carried by a second bimetallic strip connected to the second electrical terminal.
  • a second bimetallic strip connected to the second electrical terminal.
  • the two bimetallic strips are disposed so that their temperature increase brings about deformation of the strips in equal directions. This makes operation of the device independent of the ambient temperature.
  • the bimetallic strips are of a simple type, not preformed and a low strength, so that, also assisted by the presence of the magnetic means, they are able to bring about a snap opening of the contacts so as to obtain a distance between them of the order of several millimeters.
  • the relay comprises a housing ll one end of which is closed with a housing cover part l2 molded of plastic material in which three electric terminals l3, l4 and l5 are already mounted, preferably by being molded into the plastic material of the housing cover part, for connection with an external circuit.
  • a housing cover part l2 molded of plastic material in which three electric terminals l3, l4 and l5 are already mounted, preferably by being molded into the plastic material of the housing cover part, for connection with an external circuit.
  • a bimetallic strip 20 by welding or the like, and between the terminals l4 and l5 another bimetallic strip 2l is similarly connected.
  • the first strip 20 is a simple linear elongated form, for example rectangular, while the second bimetallic strip 2l is U-shaped and has its legs 2l a , 2l b secured to terminals l4 and l5 respectively.
  • the bimetallic strip 20 carries at its free end, that is, the distal end with respect to the terminal l3, a small permanent magnet l6 which cooperates functionally with an armature l9 integral with the other bimetallic strip 2l, fastened to the bow or base zone of the U-shaped strip 2l, which is the distal zone with respect to the two terminals l4 and l5.
  • the two bimetallic strips 20 and 2l also carry respectively two contact elements l7 and l8 which are urged to remain electrically engaged in a closed circuit position by the force of attraction exerted by the functional cooperation between the permanent magnet l6 and the armature l9.
  • terminal l5 is connected to one or two power source or network terminals while the terminals l3 and l4 are connected to the other network terminal across two respective motor windings - a start winding of the motor which must be cut off after the start up of the motor, and the main winding of the motor used for a normal running operation of the motor.
  • the starting current I S Upon start up of the motor, the starting current I S , owing to the normally closed state of the contacts l7, l8, flows through the terminal l3 and the bimetallic strip 20, which is dimensioned and provided with selected electrical resistance properties so that the temperature increase in the strip 20 due to the Joule effect of the start winding current circulating therein is relatively small, so that strip 20 tends to remain substantially in its initial position relative to strip 2l even when traversed by the current.
  • the current I M of the main or normal run winding of the motor passes through the terminal l4 and into the first arm 2l a of the U-shaped bimetallic strip 2l. In the second arm 2l b of the strip 2l, therefor, a current I S + I M flows.
  • the bimetallic strip 2l is dimensioned and provided with selected electrical resistance properties so that the heating of strip 2l caused by said currents urges it to deflect in a direction opposed to the attraction of the permanent magnet l6 to a relatively greater extent than the strip 20 so that the magnetic attraction force is overcome. At that point the bimetallic strips 20 and 2l move apart with a snap action, abruptly opening the contacts l7 and l8. The starting winding is thus cut off from the power supply.
  • the current I M of the motor is such as to maintain the bimetallic strip 2l at a temperature, and hence at a deformation, sufficient for the contacts l7 and l8 to remain open and thereby the starting winding remains disconnected.
  • this relay has a relatively low consumption and typically absorbs a power less than l/l0 of a Watt in a refrigerator compressor motor application for example.
  • the snap opening of the contacts is ensured by the presence of the permanent magnet l6, so that no particular forming of the bimetallic strips needs to be provided, which can therefore work under conditions of extremely low stress, thus guaranteeing a required long fatigue life.
  • the bimetallic strips have thermal response characteristics such that, when the contacts are engaged in close circuit position, the strips tend to be deformed in a similar manner in response to ambient temperature changes to retain the contacts in closed circuit position independent of such ambient temperature changes.
  • the above explained principle of opening of the contacts is such that, with appropriate dimensioning and provision of electrical resistance properties in the parts, the distance between the open contacts can be of the order of several millimeters, thus giving assurance against the priming of electric arcs and against accidental closing of the contacts because of vibrations. This is very important from the viewpoint of meeting the national and international standard requirements.

Landscapes

  • Thermally Actuated Switches (AREA)
EP86309014A 1985-11-22 1986-11-18 Relais thermique à action retardée avec bimétal double Withdrawn EP0223599A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT48820/85A IT1183004B (it) 1985-11-22 1985-11-22 Rele' termico a ritardo, a doppio bimetallo, particolarmente adatto all'avviamento di motori per compressori di frigoriferi e simili
IT4882085 1985-11-22

Publications (1)

Publication Number Publication Date
EP0223599A2 true EP0223599A2 (fr) 1987-05-27

Family

ID=11268685

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86309014A Withdrawn EP0223599A2 (fr) 1985-11-22 1986-11-18 Relais thermique à action retardée avec bimétal double

Country Status (5)

Country Link
EP (1) EP0223599A2 (fr)
JP (1) JPS62195824A (fr)
ES (1) ES2003528A6 (fr)
FR (1) FR2590721B3 (fr)
IT (1) IT1183004B (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0590592A1 (fr) * 1992-10-02 1994-04-06 TDK Corporation Dispositif de relais ayant des thermistances PTC pour démarrage des moteurs

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0590592A1 (fr) * 1992-10-02 1994-04-06 TDK Corporation Dispositif de relais ayant des thermistances PTC pour démarrage des moteurs
US5428493A (en) * 1992-10-02 1995-06-27 Tdk Corporation Motor starting relay device having PTC thermistors

Also Published As

Publication number Publication date
IT1183004B (it) 1987-10-05
IT8548820A0 (it) 1985-11-22
FR2590721A1 (fr) 1987-05-29
FR2590721B3 (fr) 1988-01-29
JPS62195824A (ja) 1987-08-28
ES2003528A6 (es) 1988-11-01

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Legal Events

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Withdrawal date: 19871013

R18W Application withdrawn (corrected)

Effective date: 19871013

RIN1 Information on inventor provided before grant (corrected)

Inventor name: ROTULO, FABRIZIO

Inventor name: CALENDA, CIRO

Inventor name: NOTARO, GIUSEPPE