Hub motor has a lot of resistance after shorting phase wires

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cryok   1 µW

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Hub motor has a lot of resistance after shorting phase wires

Post by cryok » Mar 20 2021 7:33am

After reading some stuff online I was playing with the phase wires of my 1000w motor and controller trying to see if I can get the wheel to lock when shorted, and once I got everything back the way it was before (phase wires matching), the motor still has resistance, and throttle doesn't move the wheel (with the battery turned on and off, it's the same)

What do you think happened (which was probably caused by shorting the phase wires before), and what should I check?

Thanks!

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amberwolf   100 GW

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Re: Hub motor has a lot of resistance after shorting phase wires

Post by amberwolf » Mar 20 2021 10:54pm

If phase wires are shorted, the motor will behave as you describe.

If you had the controller powered on when you did the testing, you may have damaged the FETs in the controller, which will then be shorting the phase wires themselves.

If the motor is still hard to turn even with all wires disconnected from everything, then there is a short inside the motor itself, or between the phase wires themselves. If phase wires get hot enough, they can melt their insulation and let the wires inside touch. THis usually happens inside the axle first, because there's no airflow to carry away the heat, and the wires are forced closer together there in many cases. Similarly, the windings in the motor itself can also burn off their insulation and short.

If the motor is easy to turn with all wires disconnected, then it is probably the controller that's damaged. There are tests listed on http://ebikes.ca in the learn / troubleshooting section you can do to verify this.

If it's the motor, then if you try shorting Y-G and it increases the resistance, then unshort those and then short G-B, and if that increases the resistance then unshort those and then short Y-B.

Whichever set(s) do *not* increase the resistance to turn are the ones that are shorted together.

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markz   100 GW

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Re: Hub motor has a lot of resistance after shorting phase wires

Post by markz » Mar 21 2021 12:41am

Testing for Blown Mosfets - https://ebikes.ca/learn/troubleshooting.html

How can I measure the impedance and resistance of a BLDC motor?
https://www.quora.com/How-can-I-measure ... or?share=1

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TommyCat   10 kW

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Re: Hub motor has a lot of resistance after shorting phase wires

Post by TommyCat » Mar 21 2021 8:31am

See my completed Magic Pie V5 rear hub E-Bike build Here!

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