GB2102130A - D.C. motor tester - Google Patents

D.C. motor tester Download PDF

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Publication number
GB2102130A
GB2102130A GB08117790A GB8117790A GB2102130A GB 2102130 A GB2102130 A GB 2102130A GB 08117790 A GB08117790 A GB 08117790A GB 8117790 A GB8117790 A GB 8117790A GB 2102130 A GB2102130 A GB 2102130A
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GB
United Kingdom
Prior art keywords
output
motor
current
peak
amplifier
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Withdrawn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
GB08117790A
Inventor
James Phillips
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LYNX AUTO ELECTRIC Ltd
Original Assignee
LYNX AUTO ELECTRIC 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 LYNX AUTO ELECTRIC Ltd filed Critical LYNX AUTO ELECTRIC Ltd
Priority to GB08117790A priority Critical patent/GB2102130A/en
Publication of GB2102130A publication Critical patent/GB2102130A/en
Withdrawn legal-status Critical Current

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/34Testing dynamo-electric machines
    • G01R31/343Testing dynamo-electric machines in operation

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Tests Of Circuit Breakers, Generators, And Electric Motors (AREA)

Abstract

Method and apparatus for testing a D.C. motor in which the motor 6 is connected to a battery 4 for a predetermined period controlled by a timer 18 during which the peak current is detected and displayed on a first bargraph display, and the time taken for the current to decay from the peak value to a predetermined level is displayed on a second bargraph display. <IMAGE>

Description

SPECIFICATION D.C. motor tester This invention relates to testers for D.C. motors, and is particularly applicable to testers for starter motors such as those used in motor cars.
Conventionally D.C. motors are tested by running them at the normal speed, and applying a braking torque, so as to measure the torque required to stall the motor, so as to assess whether it is achieving the required output. This method of testing is rather clumsy, and can only give an approximate indication of the performance of the motor.
According to the present invention there is provided a method of testing a D.C. motor, comprising the steps of applying a normal operating voltage to the motor for a period which is just long enough for the current through the windings to settle to a steady value, and monitoring the resultant current waveform.
The invention also extends to apparatus for testing a D.C. motor, comprising a voltage source, switching means arranged to connect the motor to the voltage source for a predetermined short period, means for detecting the peak current, and a display device adapted to produce a display corresponding to the peak current. Preferably, the apparatus also includes means for measuring and displaying the time taken for the current to decay from its peak value, to a predetermined level such as 75% of its peak value.
The apparatus may also comprise a differentiator circuit adapted to detect discontinuities in the current waveform, and to operate an indicator if such discontinuities are detected.
One embodiment of the invention will now be described by way of example, with reference to the accompanying drawing which is a block diagram of a motor tester in accordance with the invention.
Referring to the drawing, a battery charger 2 is connected to a 1 2 volt battery 4, whose positive terminal is connected to one terminal of the motor 6 which is under test. The other terminal of the motor is connected to the negative side of the battery via the normally-open contacts 8 of a first solenoid 10, and also via the normally-open contacts 12 of a second solenoid 14, which are connected in series with a current sensing resistor 16. In use, the solenoid 10 is operated to run the motor briefly before the test, so as to bed in the brushes if it is a new motor.
The solenoid 14 is operated from a starter button 16, via timers 18 and 20, which are arranged so that the solenoid contacts can orily be closed for a period of 300 milliseconds (the time out period of timer 1 8) and cannot be closed more frequently than once every 6 seconds (the time out period of the timer 20) so as to give the battery 4 time to be recharged. When the contacts 1 2 are closed, the current through the windings of the motor builds up very rapidly to a peak, and the resulting voltage across the current sensing resistor is monitored by amplifier 22. This amplifier is biased so as to have a slightly negative output before start-up.The output of amplifier 22 is connected to a peak detector 24, so that the output of the peak detector rises steeply in accordance with the build up of the current, and this output is used to drive an LED Bargraph display 28, via a buffer amplifier 26.
The output of the buffer amplifier 26 is also passed to a divider circuit 30, which provides an output equal to 75% of the voltage at the output of the buffer. The output from the divider circuit 30 is applied to one input of a comparator 32, whose other input receives the output from amplifier 22, to which it is directly connected by a line 34. Because the output of amplifier 22 is initially negative, the output of the comparator 32 is also negative until the current waveform has built up somewhat towards the peak, when the comparator output switches from "off" to "on".
The effect of this arrangement, is that when the current waveform has reached its peak, the output from divider circuit 30 remains at 75% of the peak value, whilst the voltage on line 34 decays from 100% of the peak value, and when the voltage on line 34 drops below 75% of the peak value, the output of the comparator switches from an "on" to an "off" condition.
A timer 36 is connected to the output of the comparator, so as to be switched on when the output of the comparator goes positive during the initial period of build up of the current waveform, and to be switched off again, when the output from the comparator goes negative. The output from the timer is a voltage proportional to the time elapsed since the switching on point, and is used to drive a bargraph display 38. The arrangement is such that the display rises to a level which indicates the time taken for the current to drop to 75% of its peak value, and remain at that level until the timer is reset.
The output of the amplifier 22 also drives a differentiator 40, the purpose of which is to detect discontinuities in the waveform, which could be indicative of faulty windings in the motor. If such discontinuities are detected, a series of spikes corresponding to the faults appear at the differentiator output, and are applied to the input of a rectifier 42 which is in turn connected to a comparator 44. The effect of this arrangement, is that the comparator only produces an output, if a number of spikes are detected, so that an isolated spike resulting from mains pick-up for example, is not sufficient to cause the circuit to indicate the occurrence of a fault. The output from the comparator 44 is used to drive an indicator such as an LED, when a fault is detected.
1. A method of testing a D.C. motor, comprising the steps of applying a normal operating voltage to the motor for a period which is just long enough for the current in the windings to settle to a steady value, and monitoring the resultant current waveform.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION D.C. motor tester This invention relates to testers for D.C. motors, and is particularly applicable to testers for starter motors such as those used in motor cars. Conventionally D.C. motors are tested by running them at the normal speed, and applying a braking torque, so as to measure the torque required to stall the motor, so as to assess whether it is achieving the required output. This method of testing is rather clumsy, and can only give an approximate indication of the performance of the motor. According to the present invention there is provided a method of testing a D.C. motor, comprising the steps of applying a normal operating voltage to the motor for a period which is just long enough for the current through the windings to settle to a steady value, and monitoring the resultant current waveform. The invention also extends to apparatus for testing a D.C. motor, comprising a voltage source, switching means arranged to connect the motor to the voltage source for a predetermined short period, means for detecting the peak current, and a display device adapted to produce a display corresponding to the peak current. Preferably, the apparatus also includes means for measuring and displaying the time taken for the current to decay from its peak value, to a predetermined level such as 75% of its peak value. The apparatus may also comprise a differentiator circuit adapted to detect discontinuities in the current waveform, and to operate an indicator if such discontinuities are detected. One embodiment of the invention will now be described by way of example, with reference to the accompanying drawing which is a block diagram of a motor tester in accordance with the invention. Referring to the drawing, a battery charger 2 is connected to a 1 2 volt battery 4, whose positive terminal is connected to one terminal of the motor 6 which is under test. The other terminal of the motor is connected to the negative side of the battery via the normally-open contacts 8 of a first solenoid 10, and also via the normally-open contacts 12 of a second solenoid 14, which are connected in series with a current sensing resistor 16. In use, the solenoid 10 is operated to run the motor briefly before the test, so as to bed in the brushes if it is a new motor. The solenoid 14 is operated from a starter button 16, via timers 18 and 20, which are arranged so that the solenoid contacts can orily be closed for a period of 300 milliseconds (the time out period of timer 1 8) and cannot be closed more frequently than once every 6 seconds (the time out period of the timer 20) so as to give the battery 4 time to be recharged. When the contacts 1 2 are closed, the current through the windings of the motor builds up very rapidly to a peak, and the resulting voltage across the current sensing resistor is monitored by amplifier 22. This amplifier is biased so as to have a slightly negative output before start-up.The output of amplifier 22 is connected to a peak detector 24, so that the output of the peak detector rises steeply in accordance with the build up of the current, and this output is used to drive an LED Bargraph display 28, via a buffer amplifier 26. The output of the buffer amplifier 26 is also passed to a divider circuit 30, which provides an output equal to 75% of the voltage at the output of the buffer. The output from the divider circuit 30 is applied to one input of a comparator 32, whose other input receives the output from amplifier 22, to which it is directly connected by a line 34. Because the output of amplifier 22 is initially negative, the output of the comparator 32 is also negative until the current waveform has built up somewhat towards the peak, when the comparator output switches from "off" to "on". The effect of this arrangement, is that when the current waveform has reached its peak, the output from divider circuit 30 remains at 75% of the peak value, whilst the voltage on line 34 decays from 100% of the peak value, and when the voltage on line 34 drops below 75% of the peak value, the output of the comparator switches from an "on" to an "off" condition. A timer 36 is connected to the output of the comparator, so as to be switched on when the output of the comparator goes positive during the initial period of build up of the current waveform, and to be switched off again, when the output from the comparator goes negative. The output from the timer is a voltage proportional to the time elapsed since the switching on point, and is used to drive a bargraph display 38. The arrangement is such that the display rises to a level which indicates the time taken for the current to drop to 75% of its peak value, and remain at that level until the timer is reset. The output of the amplifier 22 also drives a differentiator 40, the purpose of which is to detect discontinuities in the waveform, which could be indicative of faulty windings in the motor. If such discontinuities are detected, a series of spikes corresponding to the faults appear at the differentiator output, and are applied to the input of a rectifier 42 which is in turn connected to a comparator 44. The effect of this arrangement, is that the comparator only produces an output, if a number of spikes are detected, so that an isolated spike resulting from mains pick-up for example, is not sufficient to cause the circuit to indicate the occurrence of a fault. The output from the comparator 44 is used to drive an indicator such as an LED, when a fault is detected. CLAIMS
1. A method of testing a D.C. motor, comprising the steps of applying a normal operating voltage to the motor for a period which is just long enough for the current in the windings to settle to a steady value, and monitoring the resultant current waveform.
2. A method according to claim 1 further comprising the step of measuring the instantaneous peak to which the current rises immediately after the motor has been connected to the supply voltage.
3. Apparatus for testing a D.C. motor, comprising a voltage source, switching means adapted to connect the motor to the voltage source for a predetermined short period, means for detecting the current in the motor windings, and a display device adapted to indicate at least the peak value of the current.
4. Apparatus according to claim 3 in which the display device is adapted to indicate the peak value of the current in a bargraph form.
5. Apparatus according to claim 3 or claim 4 further comprising means for measuring and indicating the time taken for the current to decay from its peak value to a predetermined level.
6. Apparatus according to any of claims 3, 4 or 5 further comprising detecting means adapted to detect discontinuities in the current waveforms and to operate an indicator if such discontinuities occur.
7. Apparatus according to claim 6 in which the said detecting means includes a differentiator.
8. Apparatus according to claim 3, comprising a current sensing resistor arranged to monitor the current through the motor; an amplifier connected across the current sensing resistor; a peak detector connected to the output of the amplifier and arranged to drive a first display means; a divider circuit having its input connected to the output of the amplifier and having its output connected to one input of a comparator whose other input is connected directly to the output of the amplifier and whose output is connected to a timer driving a second display means, whereby, when the current waveform rises to a peak and subsequently decays, the peak value is displayed on the first display means, and the time taken to fall below a predetermined proportion of the peak value, set by the divider circuit, is displayed on the second display means.
9. Apparatus according to claim 8 in-which each display means comprises a bargraph.
1 0. Apparatus according to any of claims 3 to 9, in which the voltage source comprises a rechargeable battery connected to charging means, and in which the battery is adapted to be connected to the motor via a solenoid circuit including a timer circuit arranged to control the time for which the motor is connected to the battery and to prevent the motor from being restarted at intervals which are less than the time required to recharge the battery.
11. A method of testing a D.C. motor substantially as herein described.
12. Apparatus for testing a D.C. motor substantially as herein described with reference to the accompanying drawings.
GB08117790A 1981-06-10 1981-06-10 D.C. motor tester Withdrawn GB2102130A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08117790A GB2102130A (en) 1981-06-10 1981-06-10 D.C. motor tester

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08117790A GB2102130A (en) 1981-06-10 1981-06-10 D.C. motor tester

Publications (1)

Publication Number Publication Date
GB2102130A true GB2102130A (en) 1983-01-26

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GB08117790A Withdrawn GB2102130A (en) 1981-06-10 1981-06-10 D.C. motor tester

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GB (1) GB2102130A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4786866A (en) * 1983-07-11 1988-11-22 Jidosha Kiki Co., Ltd. Method and apparatus for power steering
GB2337127A (en) * 1997-12-16 1999-11-10 Nsk Ltd Automotive passenger restraint and protection apparatus
CN103234757A (en) * 2013-04-24 2013-08-07 无锡市朗迪测控技术有限公司 Performance test board for automobile starter
CN105275705A (en) * 2014-07-17 2016-01-27 通用汽车环球科技运作有限责任公司 Method and apparatus to evaluate a starter for an internal combustion engine
US9249772B2 (en) 2012-08-10 2016-02-02 Remy Technologies, Llc Starter pinion engagement tester

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4786866A (en) * 1983-07-11 1988-11-22 Jidosha Kiki Co., Ltd. Method and apparatus for power steering
US7380631B2 (en) 1997-12-16 2008-06-03 Nsk Autoliv Co., Ltd. Automotive passenger restraint and protection apparatus
US7389843B2 (en) 1997-12-16 2008-06-24 Nsk Autoliv Co., Ltd. Automotive passenger restraint and protection apparatus
GB2337127B (en) * 1997-12-16 2002-08-28 Nsk Ltd Automotive passenger restaint and protection apparatus
US6561299B2 (en) 1997-12-16 2003-05-13 Nsk Autoliv Co., Ltd. Automotive passenger restraint and protection apparatus
US6843339B2 (en) 1997-12-16 2005-01-18 Nsk Autoliv Co., Ltd. Automotive passenger restraint and protection apparatus
US6997277B2 (en) 1997-12-16 2006-02-14 Nsk Autoliv Co., Ltd. Automotive passenger restraint and protection apparatus
US6257363B1 (en) 1997-12-16 2001-07-10 Nsk Ltd. Automotive passenger restraint and protection apparatus
GB2337127A (en) * 1997-12-16 1999-11-10 Nsk Ltd Automotive passenger restraint and protection apparatus
US7077231B2 (en) 1997-12-16 2006-07-18 Nsk Autoliv Co., Ltd. Automotive passenger restraint and protection apparatus
US7654572B2 (en) 1997-12-16 2010-02-02 Nsk Autoliv Co., Ltd. Automotive passenger restraint and protection apparatus
US9249772B2 (en) 2012-08-10 2016-02-02 Remy Technologies, Llc Starter pinion engagement tester
CN103234757A (en) * 2013-04-24 2013-08-07 无锡市朗迪测控技术有限公司 Performance test board for automobile starter
CN103234757B (en) * 2013-04-24 2016-04-13 无锡市朗迪测控技术有限公司 Performance test board for automobile starter
CN105275705A (en) * 2014-07-17 2016-01-27 通用汽车环球科技运作有限责任公司 Method and apparatus to evaluate a starter for an internal combustion engine
CN105275705B (en) * 2014-07-17 2017-07-18 通用汽车环球科技运作有限责任公司 The method and apparatus for assessing the starter for explosive motor

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