US3518489A - Voltage suppression circuit - Google Patents

Voltage suppression circuit Download PDF

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Publication number
US3518489A
US3518489A US718544A US3518489DA US3518489A US 3518489 A US3518489 A US 3518489A US 718544 A US718544 A US 718544A US 3518489D A US3518489D A US 3518489DA US 3518489 A US3518489 A US 3518489A
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United States
Prior art keywords
voltage
resistor
circuit
supply
load
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Expired - Lifetime
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US718544A
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English (en)
Inventor
John Robin Musham
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Associated Electrical Industries Ltd
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Associated Electrical Industries Ltd
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Publication date
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    • 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
    • H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage

Definitions

  • Some degree of suppression of transient voltages may be obtained by connecting a non-linear resistor across the supply to the load.
  • a non-linear resistor is chosen to have a resistance which is high for applied voltages up to the nominal voltage of the supply but which falls rapidly as the applied voltage is raised above the voltage of the supply.
  • the greater the amplitude of the spike in the absence of the resistor, the more heavily it is loaded by the resistor. The result is to limit the amplitude of the spikes to a value somewhat greater than the nominal value of the source voltage.
  • the power loss appears as heat in the resistor and may be sufiicient to destroy the resistor.
  • thegpresent invention provides an overvoltage protection circuit for connection in shunt with a load (which is to be protected against over-voltage), said circuit comprising a fixed resistor connected in series with a non-linear impedance which is such that its impedance falls sharply when the voltage thereacross exceeds a predetermined value, and a voltage breakdown device connected across said fixed resistor, the circuit being such that breakdown of said device occurs when the voltage across the circuit exceeds a given maximum permissible value, thereby causing the voltage applied to the non-linear impedance to exceed said predetermined value so that said circuit forms an efiectively low resistance protective shunt.
  • resistors are known under the trade name Metrosil.
  • the breakdown device breaks down and is rendered conductive, thereby connecting the nonlinear resistor directly across the supply.
  • the supply is an alternating voltage
  • the breakdown device once rendered conductive is automatically extinguished at the next current zero of the source, supply, or when the holding current is reached.
  • the Metrosil resistor draws current only during a spike and the remainder of the half cycle during which the spike occurs and the Metrosil therefore may be chosen to have a resistance/voltage characteristic which permits limiting at a voltage only slightly in excess of the nominal voltage of the supply.
  • FIG. 1 is a circuit diagram of an arrangement in accordance with one embodiment of the invention.
  • FIG. 2 is a circuit diagram of a voltage suppression circuit which is an alternative to the one shown in FIG. 1.
  • a fixed linear resistor R is connected electrically in series with a non-linear Metrosil resistor M across a load L which is fed from an AC. source S through supply lines 1 and 2.
  • the load L may include semi-conductor devices which have little capacity to withstand over-voltage.
  • a semi-conductor breakdown device in the form of a thyristor T is connected in shunt with the resistor R. There is no firing or triggering circuit provided for the thyristor T which breaks down when the voltage developed across the resistor R exceeds the forward blocking voltage of the thyristor.
  • a thyristor T having a forward blocking voltage of the order of 200 volts could, for example, be used.
  • resistor R and the non-linear Metrosil resistor M form a potentiometer across the supply.
  • the value of resistor R is chosen so that the voltage V developed across it when the supply voltage is at its nominal peak value V is just less than the thyristor breakdown voltage.
  • the voltage across the Metrosil resistor M under these conditions is arranged to be less than half V and the resistance of the resistor M will then be so high that the power dissipated in the series connected resistor M and resistor R is small.
  • the supply voltage is such that the voltage developed across tthe resistor R causes the thyristor T to break down the full supply voltage is applied to the Metrosil resistor M, which then has a low resistmice.
  • the Metrosil resistor M and the thyristor T then provide a low resistance path in shunt with the load L to absorb the over-voltage and thereby protect the load.
  • FIG. 1 employing a single thyristor T is effective in protecting the load only against over-voltage spikes of one polarity and in FIG. 2 a protection circuit employing a semi-conductor bi-directional breakdown device is shown which is capable of suppressing spikes of either polarity applied across the circuit.
  • the bi-directional device may be a Triac TR or a two-way switching bridge circuit constituted by thyristors or thyristors and diodes.
  • An overvoltage protection circuit comprising in combination:
  • the circuit being such that said voltage breakdown device breaks down when the voltage across the series connected fixed resistor and non-linear impedance exceeds a given maximum permissible value, to cause the voltage across the non-linear impedance to exceed said predetermined value and thereby to form a low resistance protective shunt.
  • nonlinear impedance comprises a resistor such that the current therethrough is proportional to the ath power of the voltage thereacross, where a is between 3 and 8.
  • a circuit as claimed in claim 1 wherein the voltage breakdown device comprises a semiconductor device.
  • a circuit as claimed in claim 1 wherein the voltage breakdown device is bi-directional, that is, it breaks down when the voltage thereacross exceeds a breakdown value in either direction.
  • a circuit as claimed in claim 1 in combination with a load to be protected and power supply means across which the load is connected, said series-connected fixed resistor and said non-linear impedance being connected in shunt 'with the load.

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  • Emergency Protection Circuit Devices (AREA)
US718544A 1967-06-02 1968-04-03 Voltage suppression circuit Expired - Lifetime US3518489A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB25479/67A GB1163795A (en) 1967-06-02 1967-06-02 Over-Voltage Protection Circuit

Publications (1)

Publication Number Publication Date
US3518489A true US3518489A (en) 1970-06-30

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ID=10228377

Family Applications (1)

Application Number Title Priority Date Filing Date
US718544A Expired - Lifetime US3518489A (en) 1967-06-02 1968-04-03 Voltage suppression circuit

Country Status (5)

Country Link
US (1) US3518489A (enrdf_load_stackoverflow)
DE (1) DE1763292A1 (enrdf_load_stackoverflow)
FR (1) FR1566130A (enrdf_load_stackoverflow)
GB (1) GB1163795A (enrdf_load_stackoverflow)
SE (1) SE331311B (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3889222A (en) * 1973-11-07 1975-06-10 Tokyo Shibaura Electric Co Surge voltage absorber
US4068279A (en) * 1976-10-28 1978-01-10 Byrnes Gerald J Power monitor
US4328523A (en) * 1979-12-28 1982-05-04 Home Oil Company Limited Method and apparatus for the protection of electrical equipment from high voltage transients
US4339783A (en) * 1978-04-21 1982-07-13 Sharp Kabushiki Kaisha Alternating current corona discharge apparatus
US4347539A (en) * 1981-06-03 1982-08-31 Westinghouse Electric Corp. Electrical equipment protective apparatus with energy balancing among parallel varistors
US4419711A (en) * 1979-12-28 1983-12-06 Seguin Herb J J Method and apparatus for the protection of electrical equipment from high voltage transients
US4814941A (en) * 1984-06-08 1989-03-21 Steelcase Inc. Power receptacle and nested line conditioner arrangement

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS515630U (enrdf_load_stackoverflow) * 1974-06-28 1976-01-16
US3947726A (en) * 1974-12-18 1976-03-30 General Electric Co. Reverse voltage surge protection for high-voltage thyristors
JPS51162943U (enrdf_load_stackoverflow) * 1975-06-19 1976-12-25
DE2850559A1 (de) * 1978-11-22 1980-05-29 Faber Castell A W Spitzer fuer minen und ummantelte aufzeichnungsstifte
DE3412264A1 (de) * 1984-04-02 1985-10-10 Steute-Schaltgerätebau G. Sölken, 4972 Löhne Schalter zum ueberwachen von bewegungsablaeufen
DE3584239D1 (de) * 1984-12-24 1991-10-31 Nippon Telegraph & Telephone Schutzschaltung.
GB8816631D0 (en) * 1988-07-13 1988-08-17 Raychem Ltd Circuit protection arrangement
IL90944A0 (en) * 1988-07-13 1990-02-09 Raychem Ltd Electrical circuit protection arrangement
US5714794A (en) * 1995-04-18 1998-02-03 Hitachi Chemical Company, Ltd. Electrostatic protective device
BE1010412A3 (nl) * 1996-07-09 1998-07-07 Philips Electronics Nv Schakelinrichting.

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3246206A (en) * 1965-02-25 1966-04-12 Gen Electric Voltage surge protector
US3418530A (en) * 1966-09-07 1968-12-24 Army Usa Electronic crowbar
US3435293A (en) * 1965-12-30 1969-03-25 Texas Instruments Inc Apparatus for providing instantaneous overload protection especially useful in protecting semiconductive devices

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3246206A (en) * 1965-02-25 1966-04-12 Gen Electric Voltage surge protector
US3435293A (en) * 1965-12-30 1969-03-25 Texas Instruments Inc Apparatus for providing instantaneous overload protection especially useful in protecting semiconductive devices
US3418530A (en) * 1966-09-07 1968-12-24 Army Usa Electronic crowbar

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3889222A (en) * 1973-11-07 1975-06-10 Tokyo Shibaura Electric Co Surge voltage absorber
US4068279A (en) * 1976-10-28 1978-01-10 Byrnes Gerald J Power monitor
US4339783A (en) * 1978-04-21 1982-07-13 Sharp Kabushiki Kaisha Alternating current corona discharge apparatus
US4328523A (en) * 1979-12-28 1982-05-04 Home Oil Company Limited Method and apparatus for the protection of electrical equipment from high voltage transients
US4419711A (en) * 1979-12-28 1983-12-06 Seguin Herb J J Method and apparatus for the protection of electrical equipment from high voltage transients
US4347539A (en) * 1981-06-03 1982-08-31 Westinghouse Electric Corp. Electrical equipment protective apparatus with energy balancing among parallel varistors
US4814941A (en) * 1984-06-08 1989-03-21 Steelcase Inc. Power receptacle and nested line conditioner arrangement

Also Published As

Publication number Publication date
SE331311B (enrdf_load_stackoverflow) 1970-12-21
GB1163795A (en) 1969-09-10
DE1763292A1 (de) 1972-01-13
FR1566130A (enrdf_load_stackoverflow) 1969-05-02

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