# Motor Controller Isolated voltage sense



## [email protected] (Oct 6, 2017)

Hello ,

I am making a motor controller using texas Picolo 28069M

I want to isolate the voltage sense signals from
Dc bus voltage 
Motor Phase voltages 

Similarly there must be a voltage filter pole frequency greater than 200hz
I have tried the recommended circuit for the IC ACPL-c87 (given below) , It works great for some time but when i load the motor , it gets blown off 
due to transients from motor (The exact reason is unknown).
Kindly help .


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## kennybobby (Aug 10, 2012)

What is your typical DC buss voltage level?

What sort of motor are you using: 3-phase AC, BLDC, etc?

If the motor phase voltage exceeds ~55 volts then the opto isolator is being over-driven and will likely blow.


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## [email protected] (Oct 6, 2017)

DC Bus is 57v

I am using PMSM motor.


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## [email protected] (Oct 6, 2017)

kennybobby said:


> What is your typical DC buss voltage level?
> 
> What sort of motor are you using: 3-phase AC, BLDC, etc?
> 
> If the motor phase voltage exceeds ~55 volts then the opto isolator is being over-driven and will likely blow.


What kind of protection devices should i use apart from scaling down the voltage divider?


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## dcb (Dec 5, 2009)

put the controller near the battery as possible and twist the battery leads, and the motor leads.


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## [email protected] (Oct 6, 2017)

I am reading about the TVS diode and its applications to suppress transients.
Can it be used in this case?


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## dcb (Dec 5, 2009)

what happened when you twisted the leads (i.e. twisted pair)? You can also twist the signal and signal returns on any remote sensors, and their supplies.

Work on this part: "(The exact reason is unknown)".


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## zaxxon (Jul 11, 2009)

Is there a voltage regulator circuit supplying voltage VDD1? What does that circuit look like? What is the voltage source and the input and output voltage levels of this voltage regulator?

What is the source voltage VDD2 ? 5 volt or 3.3 volts ? Is it driving a 3.3 volt or 5 volt capable input?


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## kennybobby (Aug 10, 2012)

Can you post a schematic of your circuit and provide the usual basic information such as pack voltage, use of BMS, motor controller voltage, frequency and current limits, motor power and rpm, etc. We have no clue what you are trying to do or equipment you are trying to use.

Are you using an H-bridge for switching, do you have flyback or freewheeling diodes across your transistors/FETs. Does this occur when you back off the "throttle" or control signal as if to be coasting? What happens to the excess energy pumped back onto the buss as this occurs--it could be raising your buss voltage way above the 55 Volt limit for the optocoupler chip.


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