Electric motor: how can I check it?

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Old 09-04-16, 09:45 AM
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Electric motor: how can I check it?

I took up the offer on our local Freecycle network of a none working garden shredder.

The storey so far...

  • Initially on pressing the start button the motor would hum but not turn.
  • Guessing that this might be the capacitor a new one was purchased and fitted.
  • Unfortunately, the motor now neither hums nor turns!
  • I've checked the new capacitor and it will hold charge.



As I understand it, the capacitor gives a power boost to get the motor turning? Where do I go from here for diagnostics? I can do some simple visual checks on the motor winding and connections but how can I check further and for things like brushes?

The shredder is a Bosche AXT 2200HP model. It has a 2200w (S6)and a 2000 (S1) rating and I assume these are the start up and running ratings?

I'm based in the UK so run things like this off the normal 240v AC home supply. Any ideas, please?

Go2it.
 
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Old 09-04-16, 10:08 AM
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Welcome to the forums from the UK.

Part 29 may be a centrifugal start switch. It's located right next to the starting capacitor.
The switch is closed at start to keep the cap connected. It opens when the motor starts.
My guess is the switch is bad.

Spare Parts for Bosch Chopper AXT 2200 HP
 
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Old 09-04-16, 12:07 PM
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Other checks?

Thanks for the reply and parts link PJmax. I found what I think is the centrifugal start switch (pt 29). If I've found the correct bit, it's a white plastic component, about 1" (2cm) long with a swinging silver coloured flap. It is located in part 14/2, the upper part of the motor cover. It's connected to the starting capacitor but located several inches away, if I have identified the right part?

Just to make sure that I haven't made a complete boo-boo, the starting procedure in the manual at http://www.free-instruction-manuals..../pa_793730.pdf makes reference to "switch 2" (not that I can find it in the manual's diagram). On my machine there is also a red and a green button, which I have assumed are the start and stop buttons. I'll keep looking for a better user manual.

Are there any other quick checks that I can make on the "dead" motor at this stage? Just looking around on the web the "stator" seemed to be thing which goes wrong. If I've got this right, its the stationary bit with wire coils on it and it can burn out?

Any pre-checks would be useful to know.

Go2it
 
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Old 09-04-16, 12:19 PM
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I've never worked on one of those machines. It's tough to tell from the parts pictorial where everything is. In the description under starting they mention holding the switch in until the unit starts and then release it. That switch may be bad. That may be the actual start switch and there may not be a centrifugal one.

I see mention of a certain knob needs to be tightened for operation.
That may indicate a safety switch is associated with that knob.

Does the motor spin freely when turned by hand ?
 
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Old 09-04-16, 01:10 PM
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Tracking down the part....

Thanks for the reply.

Yes, the diagram is quite hard to follow. I've my doubts about part 29 now as the part that I have found on my machine would not spin in any way so "centrifugal" would not apply. Am I misunderstanding how a centrifugal switch would opperate?

I've located a better user manual at Bosch AXT 2500 HP Operating Instructions Manual (Page 2 of 71) which shows the controls that I have on my machine. I have a red and green switch (so there is no switch No.2 to "rotate" from position 0 to II).

When I picked the machine up from my Freecycle buddy, it would hum when the green button was pressed but the motor/shredder wheel would not spin. Having repalced the capacitor, nothing happens at all now when the green switch is pressed! Something has changed or I've corrected one fault but there is another?

Would a capacitor hum if it was faulty? I've checked the machine's mains electricity fuse and that is OK. The new capacitor stores charge so that is OK. The old capacitor did not store charge so it was definely at fault.

To answer your question, I can just turn the motor using the shredder wheel (Shown as part 815 on the diagram in your ealier post) but it's very heavy. It's dark and rainy here in the UK now so I'll re-check the motor with the shredder wheel removed in the morning.
 
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Old 09-05-16, 04:00 AM
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Sleep on it...!

Returning, rested, to my shredder restoration project, I've had success!

Just to pick up from PJmax's suggestion to check the easy turning of the motor, yes it did and this encouraged me to keep going!

The part 29, identified by PJmax was a handy one to locate. On closer investigation, it proved to be a fail-safe switch. If the cover to the motor is removed, the switch opens, via a little lever than rests on part of the motor. It prevents the cover being removed, without also breaking the circuit.

All of us sensible DIYers would, of course, have switched off and disconnected the mains supply before attempting any internal examination of the motor. The switch does prevent experimenting and tinkering with a live motor!

However, it is quite difficult to re-assemble the machine, with its cover and ensure that the switch is closed. I must have assembled the machine, with the switch in the open position on the first occasion after having renewed the capacitor. I then blamed the capacitor!

The conclusion is that I've now assembled the machine correctly and replaced the faulty part, which was the capacitor. I've got myself a 400 ($535, 480) garden shredder for the price of a capacitor! The "dead" machine came from my local Freecycle network.

DIY rules!!

Thanks for the replies. It's good to know there are folks out there!
 
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Old 09-05-16, 08:16 AM
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Great news. Thanks for letting us know.
 
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