over-current protection in torque control model.

there is not a built in parameter for this. you will have to limit/saturate the input to the Iq_Ref_A with your own logic.

you will have to limit/saturate the input to the Iq_Ref_A with your own logic.

if overcurrent is caused by other reasons ( For example,the rising rate of fault current caused by short circuit on onearm of bridge of inverter ),then this approach does not have protective effect.It is only restricting input value.right?

correct
you should use fault protection from your drive and/or using the TZ pins (or internal comparator if your device is enabled) to shut down your PWMs

What you said is the hardware protection strategy.On this basis,if I want to add software protection,then how can I read the value of phase current from 28069M?

most people would build in a total current (sum through each phase to GND) and monitor for over current for that sort of feature

1.whether does "a total current " equal the bus current?

2.What is physical meaning of "gMotorVars.Is_A"? 

3.In my application,I want to get the effective value of A (or B or C) phase current , I do not know how to get it ?

1. in my previous post, yes by "total current" I mean total current through the motor to ground
2. Is_A = sqrt (Iq_A^2 + Id_A^2). This is the magnitude of the total current vector command through the stator
3. you have ADC readings for the shunt currents

2. Is_A = sqrt (Iq_A^2 + Id_A^2). This is the magnitude of the total current vector command through the stator

If I want to limit peak of phase current,can I use Is_A to do this?

3. you have ADC readings for the shunt currents

I am not clear.Do you mean that I can read the instantaneous current value from ADC data result register,then divide it by square root of 2 ?

 

Hello?

2. I suppose you could do this. That is what USER_MOTOR_MAX_CURRENT_A does, but that assumes Is = Iq by Id = 0

3. sorry, I don't know the answer to this one

Hi Chris, 

Could you please explain a little bit more about this "fault protection from drive/ TZ pins" ?

I also use the instaSPIN FOC HV kit and need to implement over current in the torque mode. Still trying to figure out how should we design/approach this feature.

Thanks,

Yz 

You can use two ways to implement current limit and protection.
1. To set a correct reference torque current and magnetizing current in FOC, to limit the vector sum of two currents is less than the h/w board and motor maximum current.
2. To set the TrpRef value by adjust VR1 if J7 is set to 2-3. The over current fault will trig TZ1 and turn off PWM if the voltage of Iu/v/w from amplifier is higher TrpRef.
3. Use on-chip comparator on ADCA2 channel to limit Isum, to turn off PWM or limit pwm duty if the voltage of Isum is higher than setting value from on-chip DAC for the reference of on-chip comparator .

Hi Yanming,

Thanks a lot for your reply.
1) Do you mean that I should implement something like the following equation ?

sqrt(Iq^2+I^d2) < I_limit_hw , sqrt(Iq^2+Id^2) < I_limit_motor

2) Not so sure what's VR1, TZ1. Any related TI document/reference you could point me to ?

3) From my understanding for this point, we want to reduce the current by adjusting PWM signals. But again, could you please help understand a little more what's the "ADCA2 channal" and the" voltage of Isum is higher than setting value from on-chip DAC" reference ?

Thanks,
Yz

For 1), you can limit both Id and Iq reference value, you only need to limit Iq simply if you didn't change Id reference always.
For 2) and 3), it is used to current protection for h/w and motor, not limit pwm duty. You can refer to HVKit schematic and guide, controller technical reference guide to find how to use TZ trip and on-chip comparator.

Over current protection is the same in both speed and torque control, two ways are used to implement over current protection in parallel.
1. Limit reference current, like Iq and Id, or Is=sqrt(Iq^2+Id^2), and check the sampling current (Ia, Ib, Ic). There is a over current if the absolute value of sampling current is higher than you expected.
2. Used internal on-chip or external comparator to limit the motor phase current, there is a over current fault if had a trip output from comparator. High Voltage Kit is a reference on this.