GB2186129A - AC power supply systems - Google Patents

AC power supply systems Download PDF

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Publication number
GB2186129A
GB2186129A GB08602603A GB8602603A GB2186129A GB 2186129 A GB2186129 A GB 2186129A GB 08602603 A GB08602603 A GB 08602603A GB 8602603 A GB8602603 A GB 8602603A GB 2186129 A GB2186129 A GB 2186129A
Authority
GB
United Kingdom
Prior art keywords
supply
output
backup
power supply
normal
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Withdrawn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
GB08602603A
Other versions
GB8602603D0 (en
Inventor
Hilton Law
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.)
English Electric Co Ltd
Original Assignee
English Electric Co 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 English Electric Co Ltd filed Critical English Electric Co Ltd
Priority to GB08602603A priority Critical patent/GB2186129A/en
Publication of GB8602603D0 publication Critical patent/GB8602603D0/en
Publication of GB2186129A publication Critical patent/GB2186129A/en
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
    • H02J9/062—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems for AC powered loads
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21D—NUCLEAR POWER PLANT
    • G21D1/00—Details of nuclear power plant
    • G21D1/02—Arrangements of auxiliary equipment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin

Abstract

An ac power supply system includes a rectifier (7) fed by a normal ac supply, and an inverter (11) connected to the rectifier (7) by a dc link (9), the inverter (11) being effective to invert the dc output of the receiver (7) at a required frequency to provide an ac output. A dc backup power supply of lower voltage than the normal dc output of the rectifier (7) is connected across the dc link (9) such that the ac output of the rectifier (11) is derived from the backup supply if the voltage of the output of the inverter (7) falls below that of the backup supply. The dc backup power may be derived from a backup a.c. supply. Use in pumping coolant in nuclear reactor is envisaged. <IMAGE>

Description

SPECIFICATION AC power supply systems This invention relates to ac power supply systems. In particular the invention relates to ac power supply systems for use in applications where a high degree of reliability is required of the supply system, for example where the power supply system supplies power to a drive motor for driving the cooling system of a plant. In such applications it is sometimes necessary to incorporate an auxiliary drive motor powered by an independent supply system which operates in the event of the failure of the power supply to the main drive motor.
It is an object of the present invention to provide an ac power supply system which alleviates the requirement for such an auxiliary drive motor.
According to the present invention an ac power supply system includes rectifying means fed by a normal ac supply, an inverter means connected to the rectifying means by an dc link and effective to invert the dc ouput of the rectifying means at a required frequency to provide an ac output, and a backup dc power supply of lower voltage than the normal dc output of the rectifying means connected across the dc link such that said ac output is derived from the backup supply if the voltage of said dc output falls below that of the backup supply.
Preferably the dc supply is connected across the dc link via a blocking diode.
In one particular system in accordance with the invention the backup supply is constituted by the output of a rectifying means fed by a backup ac supply.
One ac power supply system in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawing which is a schematic diagram of the system.
Referring to the drawing, the ac power supply system to be described is arranged to supply power to an electric motor 1 arranged to drive a sodium pump 3, which is in turn arranged to pump liquid sodium round the reactor tank of a nuclear reactor (not shown).
The supply system takes the form of a dedicated static variable frequency converter, indicated generally in the drawing as 5. The converter 5 comprises a three phase thyristor bridge rectifier 7 which is fed from the normal power station auxiliaries' three phase ac supply. The resultant dc output of the rectifier 7 is connected via a dc link 9 to a three phase thyristor bridge inverter 11 arranged to invert the dc voltage at the required frequency, a smoothing choke 13 being incorporated in the dc link 9. The three phase variable frequency output of the inverter 11 is connected to the motor 1 via a feeder 15.
The converter 5 also inludes a second three phase thyristor rectifier 17 which is fed by a backup three phase ac essential supply of lower voltage than the normal supply. The output of the rectifier 17 is connected, via a blocking diode 19 to the dc link 9.
In normal operation of the system the power to the motor 1 is supplied via the rectifier 7 and inverter 11 from the three phase ac normal supply. Should however the normal supply fail for example in the event of a reactor trip or have its voltage drop below that of the essential supply, the essential supply automatically provides the required power to the motor 1.
In the particular case that sufficient shutdown cooling in the event of a reactor trip is ensured by a lower motor speed that is provided during normal operation, for example 10% of full speed, if the torque of the motor 1 varies as the square of speed, the voltage required of the essential supply will be 10% of the normal supply, with a power rating of 0.1% of that of the normal supply. The blocking diode 19 prevents the flow of current from the output of the rectifier 7 to the rectifier 17 during normal operation of the system.
It will be appreciated that in some circumstances the backup essential supply will take the form of a battery. In such a case, the dc output of the battery will be connected via some form of blocking device such as a diode to the dc link.
It will also be appreciated that whilst thyristor bridge circuits are particularly suitable in the application described above by way of example, other forms of rectifiers and inverters may be used in a supply system in accordance with the invention, for example transistor circuits.
It will also be appreciated that normally there will be a number of cooling systems each having a drive motor, pump and associated electrical supply system provided for the reactor, for example four, not all the cooling systems being required to maintain adequate shutdown cooling in the event of a power failure.
1. An ac power supply system including rectifying means fed by a normal ac supply, an inverter means connected to the rectifying means by a dc link and effective to invert the dc output of the rectifying means at a required frequency to provide an ac output, and a backup dc power supply of lower voltage than the normal dc output of the rectifying means connected across the dc link such that the ac output is derived from the backup supply if the voltage of said dc output falls below that of the backup supply.
2. An ac power supply system according to Claim 1 in which the dc supply is connected across the dc link via a blocking diode.
3 An ac power supply system according to
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION AC power supply systems This invention relates to ac power supply systems. In particular the invention relates to ac power supply systems for use in applications where a high degree of reliability is required of the supply system, for example where the power supply system supplies power to a drive motor for driving the cooling system of a plant. In such applications it is sometimes necessary to incorporate an auxiliary drive motor powered by an independent supply system which operates in the event of the failure of the power supply to the main drive motor. It is an object of the present invention to provide an ac power supply system which alleviates the requirement for such an auxiliary drive motor. According to the present invention an ac power supply system includes rectifying means fed by a normal ac supply, an inverter means connected to the rectifying means by an dc link and effective to invert the dc ouput of the rectifying means at a required frequency to provide an ac output, and a backup dc power supply of lower voltage than the normal dc output of the rectifying means connected across the dc link such that said ac output is derived from the backup supply if the voltage of said dc output falls below that of the backup supply. Preferably the dc supply is connected across the dc link via a blocking diode. In one particular system in accordance with the invention the backup supply is constituted by the output of a rectifying means fed by a backup ac supply. One ac power supply system in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawing which is a schematic diagram of the system. Referring to the drawing, the ac power supply system to be described is arranged to supply power to an electric motor 1 arranged to drive a sodium pump 3, which is in turn arranged to pump liquid sodium round the reactor tank of a nuclear reactor (not shown). The supply system takes the form of a dedicated static variable frequency converter, indicated generally in the drawing as 5. The converter 5 comprises a three phase thyristor bridge rectifier 7 which is fed from the normal power station auxiliaries' three phase ac supply. The resultant dc output of the rectifier 7 is connected via a dc link 9 to a three phase thyristor bridge inverter 11 arranged to invert the dc voltage at the required frequency, a smoothing choke 13 being incorporated in the dc link 9. The three phase variable frequency output of the inverter 11 is connected to the motor 1 via a feeder 15. The converter 5 also inludes a second three phase thyristor rectifier 17 which is fed by a backup three phase ac essential supply of lower voltage than the normal supply. The output of the rectifier 17 is connected, via a blocking diode 19 to the dc link 9. In normal operation of the system the power to the motor 1 is supplied via the rectifier 7 and inverter 11 from the three phase ac normal supply. Should however the normal supply fail for example in the event of a reactor trip or have its voltage drop below that of the essential supply, the essential supply automatically provides the required power to the motor 1. In the particular case that sufficient shutdown cooling in the event of a reactor trip is ensured by a lower motor speed that is provided during normal operation, for example 10% of full speed, if the torque of the motor 1 varies as the square of speed, the voltage required of the essential supply will be 10% of the normal supply, with a power rating of 0.1% of that of the normal supply. The blocking diode 19 prevents the flow of current from the output of the rectifier 7 to the rectifier 17 during normal operation of the system. It will be appreciated that in some circumstances the backup essential supply will take the form of a battery. In such a case, the dc output of the battery will be connected via some form of blocking device such as a diode to the dc link. It will also be appreciated that whilst thyristor bridge circuits are particularly suitable in the application described above by way of example, other forms of rectifiers and inverters may be used in a supply system in accordance with the invention, for example transistor circuits. It will also be appreciated that normally there will be a number of cooling systems each having a drive motor, pump and associated electrical supply system provided for the reactor, for example four, not all the cooling systems being required to maintain adequate shutdown cooling in the event of a power failure. CLAIMS
1. An ac power supply system including rectifying means fed by a normal ac supply, an inverter means connected to the rectifying means by a dc link and effective to invert the dc output of the rectifying means at a required frequency to provide an ac output, and a backup dc power supply of lower voltage than the normal dc output of the rectifying means connected across the dc link such that the ac output is derived from the backup supply if the voltage of said dc output falls below that of the backup supply.
2. An ac power supply system according to Claim 1 in which the dc supply is connected across the dc link via a blocking diode.
3 An ac power supply system according to either one of the preceding claims in which the backup supply is connected by the output of a rectifying means fed by a backup ac supply.
4. An ac power supply system substantially as hereinbefore described with reference to the accompanying drawing.
GB08602603A 1986-02-03 1986-02-03 AC power supply systems Withdrawn GB2186129A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08602603A GB2186129A (en) 1986-02-03 1986-02-03 AC power supply systems

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08602603A GB2186129A (en) 1986-02-03 1986-02-03 AC power supply systems

Publications (2)

Publication Number Publication Date
GB8602603D0 GB8602603D0 (en) 1986-03-12
GB2186129A true GB2186129A (en) 1987-08-05

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB08602603A Withdrawn GB2186129A (en) 1986-02-03 1986-02-03 AC power supply systems

Country Status (1)

Country Link
GB (1) GB2186129A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9742338B2 (en) 2013-06-21 2017-08-22 Danfoss Power Electronics A/S Dual power mode drive

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0051533A2 (en) * 1980-11-03 1982-05-12 FAIRCHILD CAMERA &amp; INSTRUMENT CORPORATION MOS battery backup controller for microcomputer random access memory
US4340823A (en) * 1980-05-07 1982-07-20 Tokyo Shibaura Denki Kabushiki Kaisha Uninterruptible power supply

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4340823A (en) * 1980-05-07 1982-07-20 Tokyo Shibaura Denki Kabushiki Kaisha Uninterruptible power supply
EP0051533A2 (en) * 1980-11-03 1982-05-12 FAIRCHILD CAMERA &amp; INSTRUMENT CORPORATION MOS battery backup controller for microcomputer random access memory

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9742338B2 (en) 2013-06-21 2017-08-22 Danfoss Power Electronics A/S Dual power mode drive

Also Published As

Publication number Publication date
GB8602603D0 (en) 1986-03-12

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