8xx fan motor continuity?

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8xx fan motor continuity?

Postby Brett » November 5th, 2018, 5:55 am

Got an 8xx machine here that the fan is not running. I know these motors are more hi-tech...

There is no continuity across the fan connectors (grey/black wires - there is no break in the wires they have continuity) - is this a problem or normal for these motors?

If I remember correctly you cannot test run the fan by applying DC to it - is that correct?

TIA!

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Re: 8xx fan motor continuity?

Postby TechGuy » November 5th, 2018, 10:08 am

I worked on an 880 vacuum motor a few weeks ago. It got low ohm. But the motor was not turning because a foreign particle was jamming the fan blade from rotating. After disassembly, I applied DC power to the motor and it ran. The motor looks like the one on 500/600/700 series vacuum motor.
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Re: 8xx fan motor continuity?

Postby mfortuna » November 5th, 2018, 12:45 pm

If this is a brush type motor try turning it by hand or even spraying motor cleaner into it. One of the brushes may not be making contact.
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Re: 8xx fan motor continuity?

Postby Brett » November 6th, 2018, 2:00 am

New one installed vs old (I think it might have got a bit wet? - Heh!)
Image
> Motor/impeller turns freely and smoothly - no probs there.
> I'm under the impression it's brushless, but I don't know for sure?
> It's definitely different to the 5/6/7xx motors.
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Re: 8xx fan motor continuity?

Postby mfortuna » November 6th, 2018, 7:39 am

That looks like a brushless motor
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Re: 8xx fan motor continuity?

Postby Brett » November 6th, 2018, 9:38 pm

Thanks. But my lack of knowledge on these is still doing my head in!

I am under the impression that a brushless motor requires 3 leads (certainly my RC plane motor does). But this has only two - the grey and black. It is possible that the robot is sending some sort of signal (PWM?) to the motor which it is interpreting internally and then driving the phases of the motor as needed.

I am still inclined to think that the fact that there is no continuity between the black and grey wires means that the motor is dead? Can anybody confirm this?
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Re: 8xx fan motor continuity?

Postby mfortuna » November 7th, 2018, 11:57 pm

A brushless motor with two leads has circuitry to perform the 3 phase PWM to run a brushless motor. If the rusted out part only contains magnets it is brushless.

Did you measure the new motor for continuity?
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Re: 8xx fan motor continuity?

Postby Brett » November 8th, 2018, 11:19 pm

Yes! There is none - open circuit. I'm thinking that means the new (used) motor is dead?
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