GB2143653A - Electric motor speed control - Google Patents

Electric motor speed control Download PDF

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Publication number
GB2143653A
GB2143653A GB08319616A GB8319616A GB2143653A GB 2143653 A GB2143653 A GB 2143653A GB 08319616 A GB08319616 A GB 08319616A GB 8319616 A GB8319616 A GB 8319616A GB 2143653 A GB2143653 A GB 2143653A
Authority
GB
United Kingdom
Prior art keywords
speed
motor
field
current
electric motor
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Withdrawn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
GB08319616A
Other versions
GB8319616D0 (en
Inventor
Robert Hailey
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.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Priority to GB08319616A priority Critical patent/GB2143653A/en
Publication of GB8319616D0 publication Critical patent/GB8319616D0/en
Publication of GB2143653A publication Critical patent/GB2143653A/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • H02P7/00—Arrangements for regulating or controlling the speed or torque of electric DC motors
    • H02P7/06—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current
    • H02P7/18—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power
    • H02P7/24—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices
    • H02P7/28—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices
    • H02P7/282—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices controlling field supply only

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

Abstract

In an arrangement for controlling the speed of an electric motor to give maximum efficiency and torque over a wide and manually variable speed range without direct control of the total, and possibly large, electric current taken by the motor armature 3, the voltage dropped across 6, representing the armature current and thus the motor speed, is used to control the current in a field winding 2. Potentiometer 7 can be set manually to prevent the field current falling below a set minimum thereby preventing motor overspeed. <IMAGE>

Description

SPECIFICATION Electric motor speed control This invention relates to the speed control of an electric motor.
It is often necessary to electronically control the speed of an electric motor. There are methods of speed control which use either a variable resistance or an intermittent power supply, the on/off ratio of which can be adjusted.
Both of these systems have disadvantages in that they reduce the overall power of the motor, they do not allow the motor to produce its maximum turning force at any given speed and they control the total current passing through the motor which in some cases can be very large, needing heavy and expensive equipment.
It is well known that the efficiency of an electric motor depends on its reverse electro-motive force, E.M.F, at maximum speed an electric motor will pass a lower current than art a lower speed, this being due to the fact that the reverse E.M.F. is higher at high motor speed so giving greater efficiency.
This reverse E.M.F. is produced by the armature windings passing through the magnetic field of the field windings, a greater reverse E.M.F. being produced when the armature passes quickly through a strong magnetic field than when it passes slowly through a weaker field.
The reverse E.M.F. and so the maximum motor speed, therefore depends on the magnetic strength of the field windings.
An electric motor with a magnetically strong field winding will produce a large turning force, due to the powerful attraction of the armature to the field windings, but will be limited, by the reverse E.M.F. to a low speed.
An electric motor with a magnetically weaker field winding will produce less turning force but will run art a much higher speed.
According to the present invention there is provided a means of automatically adjusting the magnetic strength of the field windings, to provide, according to motor speed, maximum efficiency and turning force, also a means of manually controlling the minimum magnetic strength of the field wind ings, so limiting the maximum motor speed without loss of efficiency or turning force at this or any lower speed.
To do the above by controlling the power supply to the field windings only, the larger armature current is not directly controlled.
An example of the invention will now be described with reference to the accompanying drawing.
The motor 1 has one end of its field winding connected to one side of the armature windings 3.
This junction is connected to the power supply line 8.
The other side of the armature winding is connected to the power supply 9, via a wire 6, which has a small resistance, it is the voltage drop along this wire, which is dependant on the current passing through it, which monitors the speed of the motor.
The voltage generated across the wire 6 is fed to amplifier 5 which will supply a proportional current to the free end of the field winding, 2.
Manual speed control is given by variable potentiometer 7, connected across the supply terminals 8 and 9, which feeds a variable reference voltage to amplifier 4, which will also supply a proportional current to the free end of the field windings, so preventing the field current from falling below a set minimum.
1. To automatically control the current/voltage supply to the field winding of an electric motor in order to allow the motor to run at maximum efficiency at any given speed.
2. To automatically control the current/voltage supply to the field windings of an electric motor in order to allow the motor to produce a maximum turning force at any given speed.
3. To manually limitthe minimum current/voltage supply to the field windings of an electric motor to allow variable motor speed control without loss of efficiency or turning force at this or any lower speed, as claims 1 and 2.
4. To control the speed of an electric motor by controlling a small proportion of the total motor current, that is the field winding current, only.
5. A motor control system substantially as described herein with reference to the accompanying drawing.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electric motor speed control This invention relates to the speed control of an electric motor. It is often necessary to electronically control the speed of an electric motor. There are methods of speed control which use either a variable resistance or an intermittent power supply, the on/off ratio of which can be adjusted. Both of these systems have disadvantages in that they reduce the overall power of the motor, they do not allow the motor to produce its maximum turning force at any given speed and they control the total current passing through the motor which in some cases can be very large, needing heavy and expensive equipment. It is well known that the efficiency of an electric motor depends on its reverse electro-motive force, E.M.F, at maximum speed an electric motor will pass a lower current than art a lower speed, this being due to the fact that the reverse E.M.F. is higher at high motor speed so giving greater efficiency. This reverse E.M.F. is produced by the armature windings passing through the magnetic field of the field windings, a greater reverse E.M.F. being produced when the armature passes quickly through a strong magnetic field than when it passes slowly through a weaker field. The reverse E.M.F. and so the maximum motor speed, therefore depends on the magnetic strength of the field windings. An electric motor with a magnetically strong field winding will produce a large turning force, due to the powerful attraction of the armature to the field windings, but will be limited, by the reverse E.M.F. to a low speed. An electric motor with a magnetically weaker field winding will produce less turning force but will run art a much higher speed. According to the present invention there is provided a means of automatically adjusting the magnetic strength of the field windings, to provide, according to motor speed, maximum efficiency and turning force, also a means of manually controlling the minimum magnetic strength of the field wind ings, so limiting the maximum motor speed without loss of efficiency or turning force at this or any lower speed. To do the above by controlling the power supply to the field windings only, the larger armature current is not directly controlled. An example of the invention will now be described with reference to the accompanying drawing. The motor 1 has one end of its field winding connected to one side of the armature windings 3. This junction is connected to the power supply line 8. The other side of the armature winding is connected to the power supply 9, via a wire 6, which has a small resistance, it is the voltage drop along this wire, which is dependant on the current passing through it, which monitors the speed of the motor. The voltage generated across the wire 6 is fed to amplifier 5 which will supply a proportional current to the free end of the field winding, 2. Manual speed control is given by variable potentiometer 7, connected across the supply terminals 8 and 9, which feeds a variable reference voltage to amplifier 4, which will also supply a proportional current to the free end of the field windings, so preventing the field current from falling below a set minimum. CLAIMS
1. To automatically control the current/voltage supply to the field winding of an electric motor in order to allow the motor to run at maximum efficiency at any given speed.
2. To automatically control the current/voltage supply to the field windings of an electric motor in order to allow the motor to produce a maximum turning force at any given speed.
3. To manually limitthe minimum current/voltage supply to the field windings of an electric motor to allow variable motor speed control without loss of efficiency or turning force at this or any lower speed, as claims 1 and 2.
4. To control the speed of an electric motor by controlling a small proportion of the total motor current, that is the field winding current, only.
5. A motor control system substantially as described herein with reference to the accompanying drawing.
GB08319616A 1983-07-20 1983-07-20 Electric motor speed control Withdrawn GB2143653A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08319616A GB2143653A (en) 1983-07-20 1983-07-20 Electric motor speed control

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08319616A GB2143653A (en) 1983-07-20 1983-07-20 Electric motor speed control

Publications (2)

Publication Number Publication Date
GB8319616D0 GB8319616D0 (en) 1983-08-24
GB2143653A true GB2143653A (en) 1985-02-13

Family

ID=10546024

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08319616A Withdrawn GB2143653A (en) 1983-07-20 1983-07-20 Electric motor speed control

Country Status (1)

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GB (1) GB2143653A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2357163A (en) * 1999-09-21 2001-06-13 Sturdy Francis Nagle & Co Ltd Electric motor power control device

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB281024A (en) * 1926-08-28 1927-11-28 British Thomson Houston Co Ltd Improvements in and relating to systems of electric motor control
GB283155A (en) * 1927-01-05 1928-08-23 British Thomson Houston Co Ltd Improvements in and relating to electric motor control systems
GB353541A (en) * 1929-04-30 1931-07-30 Electrical Research Products Inc.
GB399236A (en) * 1931-04-17 1933-10-05 British Thomson Houston Co Ltd Improvements in and relating to electric regulators
GB626202A (en) * 1946-08-14 1949-07-11 English Electric Co Ltd Improvements relating to automatic electric regulators
GB661765A (en) * 1949-03-09 1951-11-28 Scott L & Electromotors Ltd Improvements in means for signalling speed changes of a rotary machine and adaptablefor governing the speed of such machine
GB672686A (en) * 1948-11-29 1952-05-28 Vickers Electrical Co Ltd Improvements relating to speed control systems for direct current motors
GB883923A (en) * 1958-09-22 1961-12-06 Gen Electric Improvements in control systems for d.c. motors
GB1136258A (en) * 1966-04-27 1968-12-11 Ass Elect Ind Electric motor speed control arrangements
GB1192874A (en) * 1968-05-13 1970-05-20 English Electric Co Ltd D.C. Crane Motor Control Systems
GB1228410A (en) * 1968-01-22 1971-04-15
GB1307643A (en) * 1969-05-24 1973-02-21 Licentia Gmbh Device for the control and regulation of a direct-current motor

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB281024A (en) * 1926-08-28 1927-11-28 British Thomson Houston Co Ltd Improvements in and relating to systems of electric motor control
GB283155A (en) * 1927-01-05 1928-08-23 British Thomson Houston Co Ltd Improvements in and relating to electric motor control systems
GB353541A (en) * 1929-04-30 1931-07-30 Electrical Research Products Inc.
GB399236A (en) * 1931-04-17 1933-10-05 British Thomson Houston Co Ltd Improvements in and relating to electric regulators
GB626202A (en) * 1946-08-14 1949-07-11 English Electric Co Ltd Improvements relating to automatic electric regulators
GB672686A (en) * 1948-11-29 1952-05-28 Vickers Electrical Co Ltd Improvements relating to speed control systems for direct current motors
GB661765A (en) * 1949-03-09 1951-11-28 Scott L & Electromotors Ltd Improvements in means for signalling speed changes of a rotary machine and adaptablefor governing the speed of such machine
GB883923A (en) * 1958-09-22 1961-12-06 Gen Electric Improvements in control systems for d.c. motors
GB1136258A (en) * 1966-04-27 1968-12-11 Ass Elect Ind Electric motor speed control arrangements
GB1228410A (en) * 1968-01-22 1971-04-15
GB1192874A (en) * 1968-05-13 1970-05-20 English Electric Co Ltd D.C. Crane Motor Control Systems
GB1307643A (en) * 1969-05-24 1973-02-21 Licentia Gmbh Device for the control and regulation of a direct-current motor

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2357163A (en) * 1999-09-21 2001-06-13 Sturdy Francis Nagle & Co Ltd Electric motor power control device
GB2357163B (en) * 1999-09-21 2003-04-30 Sturdy Francis Nagle & Co Ltd A power control device

Also Published As

Publication number Publication date
GB8319616D0 (en) 1983-08-24

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