Motor not starting
 

I'm installing an ESC and brushless motor in my car. I got the ESC + motor used so I was trying to test them.

What I'm seeing now is that the motor will start and run if the shaft is at certain angles, and it won't start if it's at others.

The shaft appears to have 6 difference positions it can sit in in one rotation. If the motor is in 2/6 of the positions, it won't run when I tap the trigger. If it's in the other 4/6 it will run.

The ESC is a Novak Kinetic 2S. I did the Hall effect sensor test and the lights seem to change correctly as I rotate the shaft.

The motor is an LRP X20 13.5T brushless.

Does this sound familiar to anyone? Any ideas? Or should I just resolder all my connections?

Thanks,
Ben

Unplug the sensor wire and see if it runs right. If it does, probably a bad esc or hall effect sensor. I know you said it tested good..but

Try a different sensor wire also.

Thanks for the tips.

@spookie, I tried no sensor wire, but the ESC just threw an error that the sensor harness was missing, so the ESC must not like running in that mode.

@Andy, I only have one wire here, unfortunately. I tried reversing it, just to see if the behavior changed but it didn't.

Any other ideas?

Thanks,
Ben

We did a number of tests. I'm still not sure what's the issue.

From some tests on Helifreak (title: testing suspect motors...before frying everything, from 2009, am not allowed to post links yet), running the motor in a drill produces the same AC voltages across all pairs of connections. With all three phases of the motor shorted it seems to run smooth.

We moved the ABC connections on the ESC to BCA (same order, just shifted one). The motor still refuses to start from the same angles as before. The idea here was to identify if a driver transistor attached to one of the A/B/C poles was dead. It seems like if it was the ESC, this angle would have changed.

Edit (after the fact, 7-23-2016): If anyone from the future comes and finds this thread, I don't think the ABC->BCA test is such a great idea anymore. Maybe in sensorless mode, but it doesn't make sense to me that this'd work in sensored mode. I think the sensor wire would have to change as well.

The voltage across each pair of terminals when the motor is running appears to be the same (it will run -- it just doesn't start from certain angles).

If I hold the rotor with my fingers, I can feel a very light bumping when I try to start the motor from the position that doesn't start. When it rolls over to one of the other angles, it easily overpowers me and runs.

The lights on the ESC show 6 unique patterns in the Hall effect test. It doesn't seem to be confusing them.

We tested the Hall effect wire with an ohm meter. It all checked out. The pins on the ESC and the motor look good.

Anytime I change ESC & Motor I always Recalibrate the Motor to ESC First. Before doing this I check The Binding of TX to RX. It makes it easier to troubleshoot it before looking at sensor cable. I think sensor cables not important cuz, sensored or sensorless it'll run. Cable for boost or turbo adjust for one that uses it. Cover the basics first before making it a big problem of you purchasing a used product.

@ Geezatec, thanks for the suggestions. I've checked the RX and TX. I can use the turning servo fine, and the motor at least tries to run on command.

The new interesting thing I found was that reverse doesn't seem to work, and I can tell the ESC to reverse the drive and the motor refuses to turn in the new forward direction (if that makes sense). It makes a little buzzing sound. I'm going to dissect it later and see if there is any physical evidence of weirdness happening inside.

Can you try the esc with a known good motor?

Make sure all trims at 120'clock and EPA set at 100%. Reverse set the ESC for reverse, maybe set on brake only. Read manual on model or ESC setup.
Do one thing at the time.

Sensor board.

As has been stated several times, including by ESC representatives, the ESC is only calibrated to the radio system. The motor is not calibrated to the ESC or vice versa.

Dave's right. I'm really leaning towards a hoky esc. An esc mosfet breaking down under a voltage load? You can only do so much testing before you have to try switching parts to eliminate.

I got to experience that cold chill when you switch on you're MM last weekend and nothing happens. It was the switch woo :blush: .

Just call Novak. Oh wait...



Guessing there will be quite a few used Novak systems coming up for sale.

@spookie, you were on the money! Looks like it was the ESC.

On an ohm meter showed the '-' and 'B' terminals were shorted together. Given how well the motor looked and tested, I just gambled on a HobbyWing ESC and got it in the mail.

This kinda makes sense. The detail I sneakily withheld at the start of this thread is that when we first hooked the ESC and motor up, we had the battery backwards. My undergraduate degree is in electrical engineering and my dad (who was working with me on this) is a lifelong ham radio guy, so it seems appropriate we'd mess something like this up haha.

I just wanted to fully think this through since things seemed semi-functional.

Thanks for the help!
Ben

P.S. if anyone is looking for a 2 pole ESC just let me know...

That'll do it every time!!!