MCT8316ZTEVM: Phase Current

Tahir Mahmood

Part Number: MCT8316ZTEVM

Tool/software:

I am currently using MCT8316ZTEVM with hall sensors. I see some strange things in the current waverform.Initially the current is zero on both side of the waveform when the phase A is activated. But after some time one can see that the current is not symmtrical. The waveform is not balanced on the both side when the Phase A is activated. The current is not zero on one side and it is zero on the other side.

I am sending you the current waveform. THis happens on all the phases. What can be the reason?

2 months ago

0 Sachin S 2 months ago

TI__Expert 6011 points

Hi Tahir,

Could you check the position of the hall sensors? Usually when the hall sensors are misaligned this can happen. Basically phase U, V and W along with hall U, V and W needs to be sequentially correct.

Could you maybe check if this is correct and let me know?

Regards,

Sachin S

0 Venkatadri Shantaram84961 2 months ago

TI__Mastermind 23182 points

Hi Tahir,

Can you share motor winding resistance and ILIMIT setting?

I need to verify if this is due to resistance.

Device starts with Align phase and then follows hall sensor to commutate.

The current seems to be dropping from the initial set point which appears like resistance change .

Thanks and Best regards

Venkatadri S

0 Tahir Mahmood 2 months ago in reply to Venkatadri Shantaram84961

Expert 1250 points

The phase to phase resistance is 1.4 Ohms. It means phase resistance is 0.7 Ohm. I have not chnaged anything on the EVM board, The test point has ILIM = 1.25V which measn 8A limit.

0 Tahir Mahmood 2 months ago in reply to Venkatadri Shantaram84961

Expert 1250 points

I have measured the the two Hall sensors 1 and 2. The green is Hall sesnor 1 and Blue is hall sensor 2. At the bottom is phase voltage A. Red is phase A currrent.

0 Venkatadri Shantaram84961 2 months ago in reply to Tahir Mahmood

TI__Mastermind 23182 points

Hi Tahir,

Can you verify PWM MODE? AAR, ASR and Hall mode?

Looks like active demagnetization enabled, please confirm Hall mode on priority and type of HALL the motor has.

Thanks and Best regards

Venkatadri S

0 Tahir Mahmood 2 months ago in reply to Venkatadri Shantaram84961

Expert 1250 points

There are no resisitors present on the MODE pin, so the mode is high impedance mode. Digital Hall mode with ASR and AAR disabled. You can see the photograph.

0 Venkatadri Shantaram84961 2 months ago in reply to Tahir Mahmood

TI__Mastermind 23182 points

Hi Tahis,

Can you try Mode 7, along with synchronous mode we will enable AAR, ASR and see if this improves?

Thanks and Best regards

Venkatadri S

0 Tahir Mahmood 2 months ago in reply to Venkatadri Shantaram84961

Expert 1250 points

I tried MODE 7 but it did not work. The negative cycle is trimmed but PWM Signal has become worse.See the picture below.

I exchanged the Phase 1 and Phase 3 along with their Hall sensor signals in MODE 4, now it looks completey different but still the small triangles can be seen. Picture below.

If I now change to MODE7, it becomes worse as motor produces more noise but the negative portion is not present.

I have also seen that the PWM signal from the microcontroller does not work. The signal disappears sometimes and noise is produced. The evaluation board works only with external PWM signal.

0 Venkatadri Shantaram84961 2 months ago in reply to Tahir Mahmood

TI__Mastermind 23182 points

Hi Tahir,

I will verify your inputs tomorrow.

Thanks and Best regards

Venkatadri S

0 Sachin S 2 months ago in reply to Venkatadri Shantaram84961

TI__Expert 6011 points

Hi Tahir,

One suggestion here, could you try all combinations of the hall sensor by keeping the phase windings constant.

I still suspect the hall sensors may not be correctly mapped to the phases here.

Regards,

Sachin S

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MCT8316ZTEVM: Phase Current