TMS320F28027F: TMS320F28027F Encountering Motor Saturation

Did customer use themselves board or TI EVM? Did you have a more detail description on motor saturation, correct controller limits and configuration from customer? Like motor type, parameters, the condition and motor status (motor speed, phase current, input voltage) when meet problems.

This is a custom board. I do not have any information so was looking for guidance on what questions are needed to understand the problem more. You said motor type, parameters, the condition and motor status (motor speed, phase current, input voltage), anything else?

Some data

-Motor Duty Cycle

They currently read that using 3 current sensor inputs can lead to 100% duty cycle.  When they compile with the 3 option, we get a motor unable to start up. They have implemented this 3rd sensor on their board..  They would like to get to 100% duty cycle but they don’t accurately know how high they are actually going.  Is there a function/monitor for this?

 

-User.h File

There are a lot of parameters in the “user.h” file that they are un-sure that they have set correctly.  They would like to understand what each of these parameters fully means.

 

-Fault /Health Parameters

There are fault parameters that they can get from the DRV8301.  They would like to be able to get these and any others from the motor ware controller that may be important.

 

They are using a small motor with the following specs:

KV - 920

Poles -12

max current - 18A

internal resistance - 132mOhm

we have run up to 20kRPM unloaded

Input Voltage 10-17V

 

The data we have shows that the phase voltage hit the bus voltage, so they ran out of voltage overhead. They want to implement over-modulation and the 3 shunt current sensing, but have limited success. They would also like to make sure they are not hitting any artificial current limits, but do not know what that would look like.  Some additional questions:

 

1.  They have set USER_MAX_VS_MAG_PU from 0.5 to 0.666 and get a marked improvement (25%) in no load RPM. This seems to be good, but they see notes about ‘current reconstruction’ and they don’t know if everything is correct. They do not ever see a trapezoidal waveform on the scope, just a sine wave.

2. They are trying to use a 3^rd external current shunt, but are having trouble. They are unsure if they have the gains set up correctly, and the #sensors is set to 3. It just kind of vibrates. Are there more set up parameters and/or what values should we be looking at to see what is awry.

 

3. Is there a function to report ‘effort’?

 

-Motor Duty Cycle
Look at gMotorVars.Vs, gMotorVars.OverModulation, gMotorVars.VsRef, the duty will be 100% if the gMotorVars.Vs is equal to gMotorVars.OverModulation and gMotorVars.OverModulation is equal to 0.6666.

-User.h File
A: Refer to Chapter 4, especially section 4.1 and 4.6 of SPRUHJ1G(InstaSPIN-FOC and InstaSPIN-MOTION User’s Guide), some parameters need to be changed based on customer's board and motor.

-Fault /Health Parameters
A: In instSPIN project, connect the FAULT and OCTW pins to TZ pins of C2000 controller for over temperature, over current, over/under voltage faults, and use the default configuration of DRV8301. Customer can refer to the datasheet to understand the detail fault and parameter.

1. They have set USER_MAX_VS_MAG_PU from 0.5 to 0.666 and get a marked improvement (25%) in no load RPM. This seems to be good, but they see notes about ‘current reconstruction’ and they don’t know if everything is correct. They do not ever see a trapezoidal waveform on the scope, just a sine wave.
A: Reconstruct currents for over-modulation allows a field oriented control system to work even during heavy over-modulation, to improve the current sampling for FOC. Please refer to lab10a to understand the over-modulation.

2. They are trying to use a 3rd external current shunt, but are having trouble. They are unsure if they have the gains set up correctly, and the #sensors is set to 3. It just kind of vibrates. Are there more set up parameters and/or what values should we be looking at to see what is awry.
A: Customer can refer to DRV8301-HC kit or DRV8301 BoostXL boards to design the 3rd external current shunt circuit, and set "#define USER_NUM_CURRENT_SENSORS (3)" in user.h.

3. Is there a function to report ‘effort’?
A: No dedicate function in project to shown the effort, will appear on noise and current waveform of motor.