GB2132838A - Synchronous electric motor control - Google Patents

Synchronous electric motor control Download PDF

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Publication number
GB2132838A
GB2132838A GB08235754A GB8235754A GB2132838A GB 2132838 A GB2132838 A GB 2132838A GB 08235754 A GB08235754 A GB 08235754A GB 8235754 A GB8235754 A GB 8235754A GB 2132838 A GB2132838 A GB 2132838A
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GB
United Kingdom
Prior art keywords
motor
speed
turntable
resistor
frequency
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Withdrawn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
GB08235754A
Inventor
John Edward Olive Garrido
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GRIFFITHS MAVIS
Original Assignee
GRIFFITHS MAVIS
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 GRIFFITHS MAVIS filed Critical GRIFFITHS MAVIS
Priority to GB08235754A priority Critical patent/GB2132838A/en
Publication of GB2132838A publication Critical patent/GB2132838A/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Withdrawn legal-status Critical Current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
    • H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
    • H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
    • H02P25/022—Synchronous motors
    • H02P25/024—Synchronous motors controlled by supply frequency

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

Abstract

A synchronous electric motor for driving a record turntable is driven by an oscillator whose frequency can be varied to vary the speed of the turntable. The oscillator includes amplifier 11 with a feedback circuit including line 26. Varying resistor 29 varies the output frequency which is fed to the motor through transformer 16. Means may be provided for sensing and indicating the turntable speed. <IMAGE>

Description

SPECIFICATION Improvements in or relating to electric motors and controls therefor This invention relates to electric motors and controls therefor.
According to one aspect of this invention a turntable for a gramophone record is driven by a synchronous electric motor, and means are provided for varying the frequency of the input to the motor so as to vary the speed of the turntable.
According to another aspect of the invention control means for a synchronous electric motor comprises an oscillator whose output is connected to the motor input, and means for varying the output frequency of the oscillator.
The oscillator may comprise an amplifier provided with feedback means.
The output frequency may be controlled by a circuit having a variable time constant.
The circuit may comprise a variable resistor for varying the time constant.
The invention may be performed in various ways and one specific embodiment with possible modifications will now be described by way of example with reference to the accompanying drawings, in which: Figure lisa control circuit for an electric motor; and Figure 2 is a diagrammatic view of a motor and turntable.
Referring to Figure 1, a circuit for controlling an electric motor 10 (Figure 2) comprises an audio power amplifier 11 provided with a stabilized D C supply 12 receives an AC input at line 13 and provides an AC output on line 14 through capacitor 15 to transformer 16 whose output (sine wave) provides the input 17 to the motor 10.
The amplifier may be of the kind whose output is obtained from two transistors.
The input to the amplifier is through on/off switch 17' and a switch 18. In the position shown, the switch 18 is at terminal 19 and the speed of the motor can be varied as described below. In the position in which switch 18 is at terminal 20, the speed of the motor is not variable.
The AC supply is at line 21 to variable resistor 22 which is adjusted to give a desired output voltage from the transformer 16.
Line 23 connects switch terminal 19to movable element 24 of variable resistor 25 connected by feed back line 26 to line 27 between capacitor 15 and the transformer 16.
Terminal 19 is also connected to earth (chassis) 28 through variable resistors 29, 30 in series. A resistor 31 is connected between terminal 19 and movable element 32 of resistor 29 and a capacitor 33 is connected between earth and the junction 34 between resistor 31 and element 32.
When switch 18 is at terminal 19, as shown, resistor 25 is adjusted to give a desired output voltage from the transformer 16.
The movable element 32 can be adjusted through a centre, upright, position and the resistor 30 is adjusted so that the motor 10 is running at a desired speed when the element 32 is in the upright position of adjustment.
The motor 10 is an AC synchronous motor, preferably an induction motor, so that the motor speed can be varied by varying the frequency of the input supply to the motor. This variation in frequency is obtained by adjusting resistor 29.
The feedback line 26 in effect turns the amplifier into an oscillator which normally oscillates at 50 cycles per second but which frequency can be changed by changing the time constant of the circuit containing components 29, 30, 31,33.
In one arrangement for example in which the motor 10 is arranged for driving a gramophone turntable 41 through transmission 41' the speed of the turntable may be adjustable continuously between 10 revolutions per minute and 100 revolutions per minute by varying the speed of the motor.
In one example in which the amplifier 11 provides 30 watts output from a 30v DC supply at 12, the component values may be: Supply 21: 6.3 v AC resistor 22: 4.7K ohms resistor 31: 2.2K ohms resistor 29: 2.5K ohms resistor 30: 4.7K ohms resistor 25: 100K ohms capacitor 33: 1 farad polyester capacitor 15: 2200 FF The voltage on line 27 would be 12 v AC so that the transformer could be omitted if the motor is wound fora 12supply.
The apparatus may be used in dancing classes in which it is desired to play a record at a speed slightly above, or, more usually, at a speed below the proper speed for the record. The resistors 29, 30 may be arranged so that the speed may be adjusted to a greater amount below the normal record speed than above.
Additional features may be provided for example a photo-electric-sensor 50 responsive to the turntable speed through pulses reflected from the turntable may be connected to a digital device 51 to give a digital indication of turntable speed.
The speed of the turntable can be sensed by other means, for example by magnetic means.
Control circuits may be provided to stablilize the output voltage on line 27 so that it is independent of the frequency of the output signal on line 27.
The greater the frequency of the output signal on line 27, the greater the speed of the motor 10.
The arrangement has been described for use with a record turntable but it can be used for other purposes.
CLAIMS (Filed on 16.1.84) 1. A synchronous electric motor for driving a record turntable including means for varying the frequency of the input to the motor to vary the speed of the turntable.
2. A motor as claimed in claim 1, comprising an oscillator whose output is connected to the motor input, and means for varying the output frequency of
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to electric motors and controls therefor This invention relates to electric motors and controls therefor. According to one aspect of this invention a turntable for a gramophone record is driven by a synchronous electric motor, and means are provided for varying the frequency of the input to the motor so as to vary the speed of the turntable. According to another aspect of the invention control means for a synchronous electric motor comprises an oscillator whose output is connected to the motor input, and means for varying the output frequency of the oscillator. The oscillator may comprise an amplifier provided with feedback means. The output frequency may be controlled by a circuit having a variable time constant. The circuit may comprise a variable resistor for varying the time constant. The invention may be performed in various ways and one specific embodiment with possible modifications will now be described by way of example with reference to the accompanying drawings, in which: Figure lisa control circuit for an electric motor; and Figure 2 is a diagrammatic view of a motor and turntable. Referring to Figure 1, a circuit for controlling an electric motor 10 (Figure 2) comprises an audio power amplifier 11 provided with a stabilized D C supply 12 receives an AC input at line 13 and provides an AC output on line 14 through capacitor 15 to transformer 16 whose output (sine wave) provides the input 17 to the motor 10. The amplifier may be of the kind whose output is obtained from two transistors. The input to the amplifier is through on/off switch 17' and a switch 18. In the position shown, the switch 18 is at terminal 19 and the speed of the motor can be varied as described below. In the position in which switch 18 is at terminal 20, the speed of the motor is not variable. The AC supply is at line 21 to variable resistor 22 which is adjusted to give a desired output voltage from the transformer 16. Line 23 connects switch terminal 19to movable element 24 of variable resistor 25 connected by feed back line 26 to line 27 between capacitor 15 and the transformer 16. Terminal 19 is also connected to earth (chassis) 28 through variable resistors 29, 30 in series. A resistor 31 is connected between terminal 19 and movable element 32 of resistor 29 and a capacitor 33 is connected between earth and the junction 34 between resistor 31 and element 32. When switch 18 is at terminal 19, as shown, resistor 25 is adjusted to give a desired output voltage from the transformer 16. The movable element 32 can be adjusted through a centre, upright, position and the resistor 30 is adjusted so that the motor 10 is running at a desired speed when the element 32 is in the upright position of adjustment. The motor 10 is an AC synchronous motor, preferably an induction motor, so that the motor speed can be varied by varying the frequency of the input supply to the motor. This variation in frequency is obtained by adjusting resistor 29. The feedback line 26 in effect turns the amplifier into an oscillator which normally oscillates at 50 cycles per second but which frequency can be changed by changing the time constant of the circuit containing components 29, 30, 31,33. In one arrangement for example in which the motor 10 is arranged for driving a gramophone turntable 41 through transmission 41' the speed of the turntable may be adjustable continuously between 10 revolutions per minute and 100 revolutions per minute by varying the speed of the motor. In one example in which the amplifier 11 provides 30 watts output from a 30v DC supply at 12, the component values may be: Supply 21: 6.3 v AC resistor 22: 4.7K ohms resistor 31: 2.2K ohms resistor 29: 2.5K ohms resistor 30: 4.7K ohms resistor 25: 100K ohms capacitor 33: 1 farad polyester capacitor 15: 2200 FF The voltage on line 27 would be 12 v AC so that the transformer could be omitted if the motor is wound fora 12supply. The apparatus may be used in dancing classes in which it is desired to play a record at a speed slightly above, or, more usually, at a speed below the proper speed for the record. The resistors 29, 30 may be arranged so that the speed may be adjusted to a greater amount below the normal record speed than above. Additional features may be provided for example a photo-electric-sensor 50 responsive to the turntable speed through pulses reflected from the turntable may be connected to a digital device 51 to give a digital indication of turntable speed. The speed of the turntable can be sensed by other means, for example by magnetic means. Control circuits may be provided to stablilize the output voltage on line 27 so that it is independent of the frequency of the output signal on line 27. The greater the frequency of the output signal on line 27, the greater the speed of the motor 10. The arrangement has been described for use with a record turntable but it can be used for other purposes. CLAIMS (Filed on 16.1.84)
1. A synchronous electric motor for driving a record turntable including means for varying the frequency of the input to the motor to vary the speed of the turntable.
2. A motor as claimed in claim 1, comprising an oscillator whose output is connected to the motor input, and means for varying the output frequency of the oscillator.
3. A synchronous electric motor having control means comprising an oscillator whose output is connected to the motor input, and means for varying the output frequency of the oscillator.
4. A motor as claimed in claim 2 or claim 3, in which the output frequency is controled by a circuit having a variable time constant.
5. A motor as claimed in claim 4, in which the circuit includes a variable resistorforvarying the time constant.
6. An electric motor substantially as hereinbefore described with reference to the accompanying drawings.
7. A gramophone record turntable driven by a motor as claimed in any preceding claim.
8. Aturntablefora gramophone record adapted to be driven by a synchronous electric motor with means for varying the input frequency to the motor to vary the speed of the turntable.
9. A turntable as claimed in claim 7 or claim 8 with means for sensing the turntable speed.
10. Control means for a synchronous electric motor comprising an oscillator whose output may be connected to the motor input, and means for varying the output frequency.
GB08235754A 1982-12-15 1982-12-15 Synchronous electric motor control Withdrawn GB2132838A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08235754A GB2132838A (en) 1982-12-15 1982-12-15 Synchronous electric motor control

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08235754A GB2132838A (en) 1982-12-15 1982-12-15 Synchronous electric motor control

Publications (1)

Publication Number Publication Date
GB2132838A true GB2132838A (en) 1984-07-11

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GB08235754A Withdrawn GB2132838A (en) 1982-12-15 1982-12-15 Synchronous electric motor control

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2422474A (en) * 2005-01-19 2006-07-26 Hanpin Electron Co Ltd Digital Audio Signal Player Comprising Turntable Having Speed And Rotation Sensors

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1068843A (en) * 1962-10-25 1967-05-17 Matsushita Electric Ind Co Ltd Synchronous motors
GB1090130A (en) * 1964-09-08 1967-11-08 Tri Tech Electric rotating machine
GB1223292A (en) * 1967-04-08 1971-02-24 Gehap Gmbh & Co Kg Electro-mechanical transducers
GB1316515A (en) * 1970-05-12 1973-05-09 Buderus Eisenwerk Circuit arrangement for a timing mechanism for a cooking appliance
GB1387534A (en) * 1973-04-10 1975-03-19 Amf Inc Brushless variable speed drive for ac synchronous motor
GB1395899A (en) * 1971-10-13 1975-05-29 British Hovercraft Corp Ltd Square wave generators with variable frequency output
GB1424363A (en) * 1973-05-02 1976-02-11 Burroughs Corp Tape transport system
GB2028031A (en) * 1978-08-02 1980-02-27 Glynwed Group Services Ltd Speed control apparatus for an A.C. miniature motor
GB1573518A (en) * 1976-05-21 1980-08-28 Seiko Instr & Electronics Synchronous electric motor control arrangements

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1068843A (en) * 1962-10-25 1967-05-17 Matsushita Electric Ind Co Ltd Synchronous motors
GB1090130A (en) * 1964-09-08 1967-11-08 Tri Tech Electric rotating machine
GB1223292A (en) * 1967-04-08 1971-02-24 Gehap Gmbh & Co Kg Electro-mechanical transducers
GB1316515A (en) * 1970-05-12 1973-05-09 Buderus Eisenwerk Circuit arrangement for a timing mechanism for a cooking appliance
GB1395899A (en) * 1971-10-13 1975-05-29 British Hovercraft Corp Ltd Square wave generators with variable frequency output
GB1387534A (en) * 1973-04-10 1975-03-19 Amf Inc Brushless variable speed drive for ac synchronous motor
GB1424363A (en) * 1973-05-02 1976-02-11 Burroughs Corp Tape transport system
GB1573518A (en) * 1976-05-21 1980-08-28 Seiko Instr & Electronics Synchronous electric motor control arrangements
GB2028031A (en) * 1978-08-02 1980-02-27 Glynwed Group Services Ltd Speed control apparatus for an A.C. miniature motor

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2422474A (en) * 2005-01-19 2006-07-26 Hanpin Electron Co Ltd Digital Audio Signal Player Comprising Turntable Having Speed And Rotation Sensors

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