EP0145774A1 - Circuit electrique de commutation d'une alimentation a courant continu multiphase sur une charge - Google Patents

Circuit electrique de commutation d'une alimentation a courant continu multiphase sur une charge

Info

Publication number
EP0145774A1
EP0145774A1 EP84902521A EP84902521A EP0145774A1 EP 0145774 A1 EP0145774 A1 EP 0145774A1 EP 84902521 A EP84902521 A EP 84902521A EP 84902521 A EP84902521 A EP 84902521A EP 0145774 A1 EP0145774 A1 EP 0145774A1
Authority
EP
European Patent Office
Prior art keywords
semiconductor rectifier
input
variable resistance
scrs
switching means
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Withdrawn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
EP84902521A
Other languages
German (de)
English (en)
Inventor
Gilbert C. Dumont
Pierre-Yves Dumont
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.)
Limitorque Ltd
Original Assignee
Limitorque Ltd
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 Limitorque Ltd filed Critical Limitorque Ltd
Publication of EP0145774A1 publication Critical patent/EP0145774A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/005—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection avoiding undesired transient conditions
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
    • H02P23/24—Controlling the direction, e.g. clockwise or counterclockwise

Definitions

  • This invention relates to an electrical circuit for switching a multi-phase a.c. supply to a load, and has particular application to reversibly switching a three phase a.c. supply to an electric motor, for running, stopping and reversing the motor.
  • the invention can be used with particular advantage to control an electric motor used to drive a valve actuator.
  • a known valve actuator for example our Limitorque Model SMC 2005* comprises a three phase electric motor which drives a reduction gearing having an output for connection to a valve to drive its valve member.
  • the reduction gearing and the motor are mounted in a heavy explosion proof cast metal housing.
  • Mounted in a compartment within the housing is a set of electrical contactors which switch a three phase electrical supply to the motor so that the motor can be stopped, started and reversed.
  • the contactors are operated by relay coils themselves driven from a single phase of the a.c. supply. RE?
  • a further variable resistance device is connected across the downstream ends of the non-linear inductances of one or more phases.
  • a three phase motor switching circuit will now be described in detail with reference to the embodiment thereof shown in the drawing.
  • the three input phases R.S.T. of an a.c. supply are fed to input terminals 20, 21, 22 and the three phase inputs of a three phase motor are connected to terminals U.V. and W.
  • Semiconductor rectifier switches in the form of triacs SCR1 - 5 control the connection of the input phases R.S.T. to the terminals U.V.W.
  • the phases are connected as follows:-
  • a relay comprising a coil RLl and switching contacts RLl - 1, 2 and 3 *
  • the relay coil RLl is energised in response to a control signal on line l6 from the control logic circuit (not shown) , the control signal being indicative that the motor is to be run forwardly.
  • Each of the relay contacts is connected in series with a dropping resistor Rg so that when the contacts are closed a suitable gate potential is derived from the a.c. supply and applied to the gates of SCRl, and 5 to fire them to a conductive state.
  • the relay RLl is released, thus opening the contacts RLl -1 to RLl - 3, thus causing the SCRs 1, and 5 to switch off and stop the motor.
  • Reverse running of the motor is controlled in a similar way by means of a relay RL - 2 having a coil energised by a reverse running signal on line 17 from the control logic circuit (not shown).
  • the relay RL2 has contacts RL2 - 1, 2, 3 which when closed, fire SCRs 2, 3 and to a conductive state.
  • the electric motor connected to the terminals U V and W essentially comprises an inductive load.
  • the triac SCRl when it has been conductive and is then switched off, transients occur which would produce spurious firing of the triac if the following precautions were not taken.
  • OMPI > - WIPO triac SCRl a substantial rapidly rising transient back emf is developed in the motor coils and the back emf is applied to SCRl.
  • the impedance presented by the switched off triac SCRl is defined predominately by the capacitances of the pn junctions on either side of the SCR's gate and thus, in the presence of the transient the SCR's equivalent circuit is two capacitors connected in series and on opposite sides of the gate electrode.
  • the rapidly rising back emf can cause charge to build up in the capacitors defined by the triacs pn junctions so as to raise the gate potential sufficiently retrigger the triac into conduction.
  • a snubber circuit comprising a snubber resistor Rs and a snubber capacitor Cs, provides a by-pass for the transient back emfs.
  • the time constant of the snubber circuit is selected so that at the a.c. frequency of the supply, the snubber circuit presents a high impedance, but at the high frequency of the transient back emfs the transient currents pass preferentially through the snubber circuit so as to by-pass SCRl, thereby to prevent the spurious firing.
  • Each of the SCRs 1 to 5 is provided with its own snubber circuit Cs Rs.
  • each of the input phases R and S can be selectively connect ⁇ ed to the terminals U V by means of the SCRs 1 to 4 5 so that the motor can be run both forwardly and backwardly.
  • An SCR behaves as a capacitor when in its "off" condition which means that the input circuit is a capacitively terminated line when the motor is de-energised or is running in one direction.
  • SCRl will produce spurious firing of SCR3 which would result in a short circuit being produced across the phases R and S.
  • a similar short circuit could be established if SCRs 2 and 3 became conductive sim ⁇ ultaneously.
  • This step wavefront has a substantially greater rate of rise than the back emfs developed upon switching off of the SCRs and consequently the snubber circuit Cs Rs associated with SCR 3 would be unable to suppress the rapid voltage rise at the cathode 2k.
  • the rapid voltage rise associated with the switching on of SCR 1 would be likely to produce spurious firing of SCR 3 as a result of the transient voltage rise raising the gate potential of SCR 3»
  • firing on SCR 3 could produce spurious firing of SCR 1 and SCRs 2 and k would interact in a similar manner.
  • Such spurious firing and short circuiting of the phases is prevented by providing in series with the SCRs 1 to 5 respective inductor coils ⁇ L1 - each provided with a core of a material exhibiting a non- linear permeability.
  • the permeability of the core varies as a non-linear function of the frequency and magnitude of the applied field, and the core is typically made of ferrite material i.e. sintered carbides or iron powder material.
  • the core may also be made of permalloy, for example, Mulypermalloy manufactured by Magnetics, a division of Spang Industries Inc., P.O. Box 391, Butler Pa, l ⁇ OOl, U.S.A. or powdered soft iron.
  • the inductor coils ⁇ , -* have the effect of reducing the rate of rise of current to which the SCRs are subjected so that no spurious firing occurs.
  • the inductors appear to operate preferentially on the rapid transients which occur upon switch on; if a solid soft iron bar is used, the core inductors are heated by the a.c. supply whilst the motor is running. Conversely if no core is used in the inductors, resonance at radio frequencies may be produced in response to switching of the SCRs 1 to 5.
  • each device 30R ⁇ 30S, 30T is a varistor which operates to clamp the input voltage to a maximum preset value, say Vtrum of its associated rectifier device.
  • Varistors have the advantage of preventing sharp dv/dt changes such as might exist with an air gap arrestor.
  • each varistor has an internal capacitance which is larger than the capacitance of each rectifier device and the presence of this upstream non-negative capacitance could result in a reflected or standing wave signal being generated when varistor 30R, 30S, 30T operates.
  • the signal may also be the result of jnanufacturing tolerances which cause a mismatch.
  • each phase which is capable of being switched to reverse the motor with a further variable resistance device 31?-, 31S which is connected between the downstream ends of the inductor coils of that phase.
  • the effect of the further resistance device 31R and 31S is to cause a circulating current to flow around the loop comprising

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Ac Motors In General (AREA)
  • Power Conversion In General (AREA)

Abstract

Un circuit électrique de commutation d'une alimentation à courant alternatif multiphasé utilise des commutateurs redresseurs à semi-conducteur SCR 1 à 5 pour commuter de manière réversible l'alimentation à un moteur électrique multiphasé de manière à pouvoir faire tourner le moteur en marche avant ou arrière. Les SCRs sont arrangés en deux groupes, l'un pour commuter l'alimentation nécessaire à la marche avant du moteur, et l'autre pour l'alimentation du moteur en marche arrière. Des éléments inducteurs DELTAL sont connectés en série avec les SCRs. Dans certaines situations, des surtensions parasites importantes peuvent se produire aux phases d'entrée, par exemple en cas de foudre, ce qui peut donner lieu à un déclenchement des SCRs. L'installation de varistors entre les phases d'entrée et la terre permet de limiter la tension d'entrée à une valeur maximum prédéterminée, empêchant ainsi le déclenchement parasite des SCRs. On décrit également l'utilisation de varistors supplémentaires permettant de réduire les effets d'ondes stationnaires de tension pouvant se produire à cause des capacitances internes du premier groupe de varistors.
EP84902521A 1983-06-16 1984-06-15 Circuit electrique de commutation d'une alimentation a courant continu multiphase sur une charge Withdrawn EP0145774A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8316441 1983-06-16
GB838316441A GB8316441D0 (en) 1983-06-16 1983-06-16 Electrical circuit

Publications (1)

Publication Number Publication Date
EP0145774A1 true EP0145774A1 (fr) 1985-06-26

Family

ID=10544329

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84902521A Withdrawn EP0145774A1 (fr) 1983-06-16 1984-06-15 Circuit electrique de commutation d'une alimentation a courant continu multiphase sur une charge

Country Status (6)

Country Link
EP (1) EP0145774A1 (fr)
AU (1) AU3069084A (fr)
GB (1) GB8316441D0 (fr)
IT (1) IT1177800B (fr)
WO (1) WO1985000079A1 (fr)
ZA (1) ZA844508B (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6966275B2 (en) * 2001-10-10 2005-11-22 Whitehill David C E Pet bed
CN110011335A (zh) * 2019-03-14 2019-07-12 南方电网科学研究院有限责任公司 零毫秒三相不平衡治理换相开关及其换相时序控制方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT998793B (it) * 1972-10-21 1976-02-20 Licentia Gmbh Dispositivo elettronico di prote zione di inversione
US4259705A (en) * 1979-03-27 1981-03-31 Stifter Francis J Combination surge suppressor filter
CA1124819A (fr) * 1979-10-26 1982-06-01 Robert F. Rose Regulateur de puissance pour alimentateur vibratoire
BE889496A (fr) * 1981-07-03 1981-11-03 Dumont Gilbert C Inverseur statique polyphase

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8500079A1 *

Also Published As

Publication number Publication date
IT1177800B (it) 1987-08-26
GB8316441D0 (en) 1983-07-20
ZA844508B (en) 1985-01-30
AU3069084A (en) 1985-01-11
WO1985000079A1 (fr) 1985-01-03
IT8448406A1 (it) 1985-12-15
IT8448406A0 (it) 1984-06-15

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Legal Events

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18D Application deemed to be withdrawn

Effective date: 19850521

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Inventor name: DUMONT, PIERRE-YVES

Inventor name: DUMONT, GILBERT, C.