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Testing Motors


m4tty

Question

Hi,

Just wondered how you would test a motor in say an electric drill. If you tested continuity between live and neutral on the plug would you get a reading showing the resistance of the windings in the motor as i tried this but got no reading. Or am thinking along the wrong lines.

Thanks in advance

Cheers

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12 answers to this question

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Did you pull the trigger ??

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you are thinking along the right lines but like EVANS ELECTRIC asked did you pull the trigger? The best is to open the handle of the drill, locate the 2 wires going to the motor and testing for continuity between the 2. If the motor is ok then you will get a reading, obviously the more windings there are in the motor the higher the resistance will be. If there is no continuity at all between the 2 then your motor windings are burnt out. Hope this is helpful.

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I did and pushed in the lock so it was definitely on but has been cutting out when used recently and was working intermittently. Think the switch may need looking at?

If all was good and working on the drill should i see the resitance when using continuity tester (low resistance ohmetre)

Cheers

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So if someone had a faulty drill and asked you to check it out would you do a continuity test or would you megger it (insulation resistance test)

Thanks again for all the help

Cheers

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This recently happened to my drill i found out that the live wire in the 3 core flex was broken about 200mm from the drill. Then again it could be the trigger on your drill.

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So if someone had a faulty drill and asked you to check it out would you do a continuity test or would you megger it (insulation resistance test)

Thanks again for all the help

Cheers

id stick the plug into a 13A socket and press the trigger...

you would need continuity to test the motor hasnt gone O/C. megger would check the insulation hasnt parted the conductors

the flexis usually the main culprit on drill (and just about any other hand tool)

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M4tty never do a insulation resistance test on any motor not between the live conductors (live and neutral) anyway. Always resistance tests.

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Ten to one its the flex, as Andy says, check the flex from plug top to trigger, check trigger , both poles, check brushes.

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Thanks everyone for all the replies but just have another question if you dont mind.

Obviously I know its AC going in but are all mains fed hand tools fitted with AC motors or do some use DC Motors with the AC being changed to DC before being fed into Motor or am i barking up wrong tree?

Also do AC Motors have carbon brushes and why do DC Motors need a commutator?

Thanks again for your time]

Cheers

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You have to be careful if the drill has variable speed control...If it does then you will probably not get a reading due to the electronics, but if it's a single speed drill then you will.

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Thanks everyone for all the replies but just have another question if you dont mind.

Obviously I know its AC going in but are all mains fed hand tools fitted with AC motors or do some use DC Motors with the AC being changed to DC before being fed into Motor or am i barking up wrong tree?

Also do AC Motors have carbon brushes and why do DC Motors need a commutator?

Thanks again for your time]

Cheers

The motors used in drills etc are parallel wound commutator motors, I.e. dc motors, but they operate happily on ac as well. Can't remember why that type of motor is used tbh. Long time since I was at college!

Keep your fault finding simple continuity test each section indvidually: flex, switch, motor, etc. As others have said, probably flex, most likely at end of flex support so if flex is open circuit chop 100mm off end and try again!

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Could also be worn brushes guys........regular occurence :)

(unless I`m missing summat?)

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