GB2055260A - Main power supply safety cutout circuit - Google Patents

Main power supply safety cutout circuit Download PDF

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Publication number
GB2055260A
GB2055260A GB8021686A GB8021686A GB2055260A GB 2055260 A GB2055260 A GB 2055260A GB 8021686 A GB8021686 A GB 8021686A GB 8021686 A GB8021686 A GB 8021686A GB 2055260 A GB2055260 A GB 2055260A
Authority
GB
United Kingdom
Prior art keywords
circuit
coil
supply
trip
mains supply
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Withdrawn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
GB8021686A
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.)
Mpac Group PLC
Original Assignee
Molins 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 Molins Ltd filed Critical Molins Ltd
Priority to GB8021686A priority Critical patent/GB2055260A/en
Publication of GB2055260A publication Critical patent/GB2055260A/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
    • H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
    • H02H3/33—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H1/00—Details of emergency protective circuit arrangements
    • H02H1/06—Arrangements for supplying operative power

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

An isolation circuit comprises an undervoltage trip coil (6) which is supplied from winding 20 of a transformer 14 and controls main contactor (4) or a moulded case circuit breaker in the main supply line (2) to a machine or group of machines supplied via lines 8, 10, 12 or 16. Rechargable batteries (34) are connected via a push-button switch (45) having double pole changeover contacts (47, 49) so that when the button (45) is not actuated, to engage controls (47), the batteries are parallel and are charged from the mains supply (2), through winding 20. When the button (45) is actuated, to engage contacts (49), the batteries are connected in series with the trip coil (6) and supply power thereto enabling the trip coil to reset the contactor (4) after it has opened in response to a fault. Use of the batteries to reset the circuit breaker makes this circuit cheaper and safer than conventional systems which use high-voltage expensive components and have unprotected high-voltage contacts. <IMAGE>

Description

SPECIFICATION Main power supply safety cut-out circuit This invention relates to safety circuits for the protection of personnel operating electrical machinery, which operate by disconnecting the main circuit in the event of the detection of an abnormal condition such as an undervoltage or an "earth leakage".
According to the present invention there is provided an isolation circuit for the main power supply to a machine or group of machines, which circuit comprises: a circuit breaking device having a trip device controlling a mains supply connection; rechargeable battery means; and a manually operable contact switch, the isolation circuit being arranged such that when the manually operable contact switch is not actuated the mains supply is connected to the battery means and, via the mains supply connection, to the trip device, and when the contact switch is actuated the battery means is arranged to supply power to the trip device.
The trip device is preferably an undervoltage trip coil and a transformer is preferably provided connected on its low voltage winding side to the trip coil and on its high voltage winding side to the mains supply via the mains supply connection.
The circuit breaking device in the main supply line i.e. the mains supply connection, may for example be a contactor or moulded case circuit breaker with thermal tripping characteristics.
Preferably, an "earth protection unit" e.g. an earth leakage circuit breaker is also connected in series with the trip coil and a security interlock system may also be incorporated, to prevent the circuit being activated when machine guards are not in position, for example.
Preferably the manually-operable contact means comprises a push-button which has changeover contacts arranged so that operation of the push-button changes the connection of the battery means from a condition in which it is connected in parallel with the trip coil so as to be charged from the mains supply via the transformer low voltage winding, to a condition in which the battery means is in series with the coil and in parallel with the transformer low voltage winding so as to supply power to the coil in place of the mains supply.
Preferably a socket is provided for connection of a starter/charger unit in the event of the batteries becoming discharged as a result of having been out of service for some time.
One embodiment of the invention will now be described by way of example, with reference to the accompanying circuit diagram.
The diagram shows an incoming three-phase supply 2 which is connected to the machines in a factory, for example a cigarette factory, via a main contactor 4 having a d.c. "undervoltage" coil 6.
Equipment which requires a three-phase supply is conrrected directly to the other side of the contactor via lines 8, 10, 12. Two of the lines 8, 12 also feed a single-phase transformer 14 which has three output windings 16, 18 and 20. The output winding 1 6 provides a single-phase machine supply, while the winding 18 provides a supply to an "earth protection" unit 22 connected in series with the undervoitage coil 6 of the contactor 4. The effect of the "earth protection" unit is to disconnect the supply to the coil if a leakage current to earth is detected.Detection of leakage currents is achieved by passing all the high-voltage leads of the circuit (i.e. 8, 10, 12 and the outputs of windings 16 and 1 8) through the protection unit, which measures the difference between the currents flowing in the "live" and "neutral" wires. If the imbalance is more than, say, 20mA, the unit is arranged to interrupt the supply to the under-voltage coil. A high security interlock device 24 is also connected in the line to the earth protection unit, to interrupt the circuit in the event of certain safety devices being in operation, such as switches associated with machine guards.
The winding 20 supplies the coil 6 with 24V when the contactor 4 is closed, via diodes 26, 28.
A battery circuit 30 is connected in parallel with diode 26 and comprises a pair of Ni-Cd accumulators 32, 34 each of which is connected to coil 20 via a respective diode 36, 38 and resistor 40 42. A push-button switch 45 having double-pole changeover contacts 47, 49 is connected into the battery circuit in such a way that when the button is not actuated so that the contacts assume the upper posItions 47, the accumulators are connected in parallel between the winding 20 and earth, i.e. in parallel with the undervoltage coil 6, so that they are charged via the diode-resistor networks, as long as the main contactor 4 is closed.When the push-button is actuated so that the contacts assume the lower positions 49, the two accumulators are connected in series between the winding 20 and the diode 28 so that they supply power (at 24V) to the undervoltage coil 6, enabling the circuit to be "started up" by latching on the contactor 4. When this happens the winding 20 will be activated, so that the accumulators will be connected in the recharging mode as soon as the push-button is released.
A socket 44 is connected to a diode 46 which is in turn connected in parallel with the diode 28 to enable a starter/charger device to be connected in the event that the batteries become discharged.
This can be a single transformer/rectifier arrangement and can be made easily movable so that only one will be required for a factory having a number of machine installations. A relay 48 is connected between the starter/charger input and earth to inhibit operation of the machine control circuits while the starter/charger is connected.
1. An isolation circuit for the main power supply to a machine or group of machines, which circuit comprises: a circuit breaking device having a trip device controlling a mains supply connection; rechargeable battery means; and a manually operable contact switch, the isolation circuit being
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Main power supply safety cut-out circuit This invention relates to safety circuits for the protection of personnel operating electrical machinery, which operate by disconnecting the main circuit in the event of the detection of an abnormal condition such as an undervoltage or an "earth leakage". According to the present invention there is provided an isolation circuit for the main power supply to a machine or group of machines, which circuit comprises: a circuit breaking device having a trip device controlling a mains supply connection; rechargeable battery means; and a manually operable contact switch, the isolation circuit being arranged such that when the manually operable contact switch is not actuated the mains supply is connected to the battery means and, via the mains supply connection, to the trip device, and when the contact switch is actuated the battery means is arranged to supply power to the trip device. The trip device is preferably an undervoltage trip coil and a transformer is preferably provided connected on its low voltage winding side to the trip coil and on its high voltage winding side to the mains supply via the mains supply connection. The circuit breaking device in the main supply line i.e. the mains supply connection, may for example be a contactor or moulded case circuit breaker with thermal tripping characteristics. Preferably, an "earth protection unit" e.g. an earth leakage circuit breaker is also connected in series with the trip coil and a security interlock system may also be incorporated, to prevent the circuit being activated when machine guards are not in position, for example. Preferably the manually-operable contact means comprises a push-button which has changeover contacts arranged so that operation of the push-button changes the connection of the battery means from a condition in which it is connected in parallel with the trip coil so as to be charged from the mains supply via the transformer low voltage winding, to a condition in which the battery means is in series with the coil and in parallel with the transformer low voltage winding so as to supply power to the coil in place of the mains supply. Preferably a socket is provided for connection of a starter/charger unit in the event of the batteries becoming discharged as a result of having been out of service for some time. One embodiment of the invention will now be described by way of example, with reference to the accompanying circuit diagram. The diagram shows an incoming three-phase supply 2 which is connected to the machines in a factory, for example a cigarette factory, via a main contactor 4 having a d.c. "undervoltage" coil 6. Equipment which requires a three-phase supply is conrrected directly to the other side of the contactor via lines 8, 10, 12. Two of the lines 8, 12 also feed a single-phase transformer 14 which has three output windings 16, 18 and 20. The output winding 1 6 provides a single-phase machine supply, while the winding 18 provides a supply to an "earth protection" unit 22 connected in series with the undervoitage coil 6 of the contactor 4. The effect of the "earth protection" unit is to disconnect the supply to the coil if a leakage current to earth is detected.Detection of leakage currents is achieved by passing all the high-voltage leads of the circuit (i.e. 8, 10, 12 and the outputs of windings 16 and 1 8) through the protection unit, which measures the difference between the currents flowing in the "live" and "neutral" wires. If the imbalance is more than, say, 20mA, the unit is arranged to interrupt the supply to the under-voltage coil. A high security interlock device 24 is also connected in the line to the earth protection unit, to interrupt the circuit in the event of certain safety devices being in operation, such as switches associated with machine guards. The winding 20 supplies the coil 6 with 24V when the contactor 4 is closed, via diodes 26, 28. A battery circuit 30 is connected in parallel with diode 26 and comprises a pair of Ni-Cd accumulators 32, 34 each of which is connected to coil 20 via a respective diode 36, 38 and resistor 40 42. A push-button switch 45 having double-pole changeover contacts 47, 49 is connected into the battery circuit in such a way that when the button is not actuated so that the contacts assume the upper posItions 47, the accumulators are connected in parallel between the winding 20 and earth, i.e. in parallel with the undervoltage coil 6, so that they are charged via the diode-resistor networks, as long as the main contactor 4 is closed.When the push-button is actuated so that the contacts assume the lower positions 49, the two accumulators are connected in series between the winding 20 and the diode 28 so that they supply power (at 24V) to the undervoltage coil 6, enabling the circuit to be "started up" by latching on the contactor 4. When this happens the winding 20 will be activated, so that the accumulators will be connected in the recharging mode as soon as the push-button is released. A socket 44 is connected to a diode 46 which is in turn connected in parallel with the diode 28 to enable a starter/charger device to be connected in the event that the batteries become discharged. This can be a single transformer/rectifier arrangement and can be made easily movable so that only one will be required for a factory having a number of machine installations. A relay 48 is connected between the starter/charger input and earth to inhibit operation of the machine control circuits while the starter/charger is connected. CLAIMS
1. An isolation circuit for the main power supply to a machine or group of machines, which circuit comprises: a circuit breaking device having a trip device controlling a mains supply connection; rechargeable battery means; and a manually operable contact switch, the isolation circuit being arranged such that when the manually operable contact switch is not actuated the mains supply is connected to the battery means and, via the mains supply connection, to the trip device, and when the contact switch is actuated the battery means is arranged to supply power to the trip device.
2. An isolation circuit according to claim 1, wherein the trip device is an undervoltage trip coil.
3. A circuit according to claim 1 or claim 2 comprising a transformer connected on its low voltage winding side to the trip coil and on its high voltage winding side to the mains supply via the mains supply connection.
4. A circuit according to any one of the preceding claims wherein the mains supply connection is a contactor.
5. A circuit according to any one of claims 1 to 3, wherein the current breaking device is a moulded case circuit breaker.
6. A circuit according to claim 4 or claim 5, wherein the circuit breaking device has thermal tripping characteristics.
7. A circuit according to any one of the preceding claims including means for detecting a leakage current to earth, and earth protection circuit breaking means connected in series with the trip device and arranged to interrupt the supply to the trip device in the event of earth leakage being detected, thereby operating the circuit breaking device.
8. A circuit according to any one of the preceding claims wherein the manually operable switch comprises a push-button with changeover contacts arranged so that when the push-button is in a non-activated state the changeover contacts connect the battery means in parallel with the trip device for charging the battery means from the mains supply, and when the push-button is in an activated state the changeover contacts connect the battery means in series with the trip device so that power is supplied from the battery means to the trip device.
9. A circuit according to any one of the preceding claims comprising means for connecting an auxiliary power supply into the circuit for supplying said trip device and/or for charging the battery means.
10. A circuit according to any one of the preceding claims comprising a security circuit breaker device connected in series with the trip device and arranged to interrupt the power supply to the trip device if any one or any preset combination of prechosen safety functions indicate unsafe conditions.
11. A circuit substantially as hereinbefore described with reference to the accompanying drawing.
12. The subject matter of any preceding claim (ignoring any dependency of one claim on another) considered separately or in combination with the subject matter of any one or more of the other claims (again ignoring dependency).
GB8021686A 1979-07-05 1980-07-02 Main power supply safety cutout circuit Withdrawn GB2055260A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8021686A GB2055260A (en) 1979-07-05 1980-07-02 Main power supply safety cutout circuit

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB7923485 1979-07-05
GB8021686A GB2055260A (en) 1979-07-05 1980-07-02 Main power supply safety cutout circuit

Publications (1)

Publication Number Publication Date
GB2055260A true GB2055260A (en) 1981-02-25

Family

ID=26272082

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8021686A Withdrawn GB2055260A (en) 1979-07-05 1980-07-02 Main power supply safety cutout circuit

Country Status (1)

Country Link
GB (1) GB2055260A (en)

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)