Dewalt 20volt brushless motor

[KevinW]

I have a brushless motor that is blowing 4 amp fuses when voltage is applied to the motor.
I don't see any faults with my ohms meter and I'm wondering what is the best way to track this fault down?
The drive has free movement so it's not mechanical.

 

[ZipZapOuch]

I have a brushless motor that is blowing 4 amp fuses when voltage is applied to the motor.
I don't see any faults with my ohms meter and I'm wondering what is the best way to track this fault down?
The drive has free movement so it's not mechanical.

I assume it is a proper brushless 3-wire motor so Measure the resistance between all combinations of leads from the brushless motor and then from each lead to ground.

Also, do you have a proper brushless motor speed controller or is the speed controller in the motor to make it a two-wire motor?

 

[KevinW]

(3 leads) 0 ohms from each of the leads, 1.5k ohms from ground to each lead.
Can I induce a small amount of voltage and look for a hot device?
How many amps and how much voltage.
It has two wires to handle the 20 volts from the battery to the motor and two more small wires that come from the switch to it's own control board attached to the motor.

 

[ZipZapOuch]

(3 leads) 0 ohms from each of the leads, 1.5k ohms from ground to each lead.
Can I induce a small amount of voltage and look for a hot device?
How many amps and how much voltage.
It has two wires to handle the 20 volts from the battery to the motor and two more small wires that come from the switch to it's own control board attached to the motor.

You'll have to post a photo - I'm not understanding something.
You say there are three leads from the motor (typical for a brushless) but,
Then you say there are only two wires from the battery to the motor. This is not typical for a brushless.

 

[MaxHeadRoom78]

You'll have to post a photo - I'm not understanding something.
You say there are three leads from the motor (typical for a brushless) but,
Then you say there are only two wires from the battery to the motor. This is not typical for a brushless.

It could be as built in Post#2. has internal commutation/controller, making it a 2-wire feed.

 

[KevinW]

The 3 wires are the windings.
The two wires are from the switch.
This is a friends pole saw, I have the same saw.
His bottom end (switch) works with my upper end saw so the switch side is good on his saw.

 

[ZipZapOuch]

It could be as built in Post#2. has internal commutation/controller, making it a 2-wire feed.

Right, but just making sure so we are all on the same page. And it appears we are now.

 

[rjenkinsgb]

Are you sure the fuse should only be 4A? That seems very low for a power tool motor - I'd expect it to be able to peak at least 20A ??

Other than that, check the resistance from the motor terminals, each way, to positive and negative power?

One of the power MOSFETs may have shorted.

If there is a short or near-short, you will have to disconnect the motor from the driver PCB and test from each motor connection pad to the input bower.

 

[KevinW]

There are two S smd fuses in parallel .
That's my next move , remove the board from the motor and inspect the other side.