Gregory wrote:To check the motor phases just put a multi metre on continuity setting , cycle through the phase combinations and check that it doesnt beep/resistance goes low.
When I do this on my motor and a spare motor every phase combination on both motors beep, isn't this normal???
heathyoung wrote: Check to see if any of the gates are energised when no throttle is applied - there will be a voltage on one of the phase leads to ground or B+.
Ok connected up the controller again, tiny bit of smoke but no noise from the damaged fets. The blown phase, yellow, has 63 volt to the battery negative and the other two phases, blue and green, have 63 volts to the battery positive.
Does this help the diagnosis?
I really appreciate peoples help here as my electronic knowledge is fairly limited.
Interesting. Not normal. Not good either.
OK - to determine if those are the gates energised or if those FETS are shorted, check the resistance between each phase and battery + and - ve.
Anything showing a reading here will be a problem (more cooked FETS). Also check between the gate (first pin of the FET) and the other pins (drain and source) - if you get continuity here, there is a very good chance that you will have problems with the gate drive resistors, and possibly transistors (as the full pack voltage has ended up here).
If these show no shorts, then you have a gate drive issue. Usually once you get to this point, it gets painful. The gate drive is usually a pair of transistors, arranged in something called a totem pole - these cheapies don't use proper gate driver IC's (at least not the ones I have fixed). What will happen is that one of the transistors will short (and when the other is energised, it will die as well) - worst comes to the worst, this will back-feed the microcontroller IO pins if not well protected.
Finding these transistors, and determining if they are shorted is a pain. You can determine if it is switching properly with an appropiatly sized resistor and an LED, with the halls connected (i actually have a pic microcontroller that fakes legitimate hall signals) and spin the wheel (no phases connected, just halls), with some throttle (so not zero PWM, but PWM only applies to one of the sides, not both - I think it is the lowside from memory) you should see the LED's flash when each MOSFET is meant to fire - any that don't flash, or stay stuck on - are problematic.
New evil decided - GNG offroad build on Craftworks DHR with 12S4P lipo. Aim - Light, balanced, powerful, able to climb a tree.
Project Vectrix restarted. Status - BMS + Charge control redesign (read faffing with batteries again)