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Other › How to tell if its the motor or ESC thats u/s ?
04-18-2011 07:50 AM  7 years agoPost 1
Paul Woodcock

rrElite Veteran

Dubai - United Arab Emirates

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Hi Guys

I have a Trex700e FBL. All stock. Motor is Align 700mx 510kv and esc is CC 120 hv.

I have had about 5 flights on it. I am still busy setting up the Vbar etc.

On Friday, had one great flight and then on the second, 30 sec into the flight, i had a big 'kick' on the tail, the motor sounded very rough, and started loosing rpm. I was in a hover, over the runway, so just clicked to hover and landed. All OK.

I checked the temp of the motor and esc with my finger and they were both cool and the motor turned freely by hand. I tried to spool up the rotors again, but motor was 'kicking' badly and wouldn't accelerate. I stopped and flew my other heli.....

On the problem flight, i had just taken off, gone to ST2 and did 2 or 3 short fast climb outs. No more than 80 throttle for 2 or 3 seconds when it went wrong.

This morning i downloaded the data off the esc. All seems OK on the first flight. Second just shows a big rpm drop and the landing. otherwise all ok.

I took the head and main gear off the heli to try the motor on the bench. When i plug the battery in, i get the 12 beeps VERY softly and the motor won't spin at all. By hand it turns over like normal.

Sorry for the long rundown of the problem, but how do you tell if its the motor or esc thats toast..... or both.

i have a 2nd machine (700 f3c) and can use its esc to test this motor and this esc to try on the f3c's motor.

I am just worried that a burnt motor could damage and esc and vice-versa.

Any advice, please.

Regards
Paul

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04-18-2011 08:28 AM  7 years agoPost 2
GyroFreak

rrProfessor

Orlando Florida ...28N 81W

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Yes, a burnt or shorted motor winding can destroy a good ESC. Use a good digital ohm meter and check the wires while disconnected from the esc. Check each of the three leads of the motor for any shorts to the motor frame. All 3 leads should show open to the frame.
Next check the ohms from each lead to the next lead. All three readings should be very close. The readings will be in the very low ohm range so use good heavy duty meter leads and digital ohm meter. You need to look up your particular motor specs for what the ohm readings should be.
If you can't find the winding ohms, go ahead and try to measure. The three readings must be very close.
I just checked my Scorpian 400KV and it measured 0.4 ohms on each leg. All three reading must be close. Also smell your motor, shorted or burnt winding can stink.
There is another way of testing the motor by spinning it with a drill and using a scope to look at the waveform on each winding.

I think about the hereafter. I go somewhere to get something, then wonder what I'm here after ?

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04-18-2011 09:10 AM  7 years agoPost 3
Paul Woodcock

rrElite Veteran

Dubai - United Arab Emirates

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Hi GyroFreak

Thanks for the info. I will get out my multi-metre and give it a good check out.

I don't have a scope, so will skip that....

Thanks.

Regards
Paul

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