ACIM MOTOR SPEED CANNOT INCREASE

[Omer Ab]

I can't increase the motor speed beyond a certain point.

For example, when using the ST Motor Pilot interface, I set the Speed Reference variable to 2500 RPM, and the Mechanical Speed reaches approximately the same value (2495 RPM). However, when I increase the Speed Reference beyond 2500 RPM, the Mechanical Speed does not increase and remains the same.

MCU: STM32G431RB
Power Board: STEVAL-IHM023V3

NOT :I increased the motor's nominal current using MC Workbench, but I didn't notice any change in speed.

[VERSION]: MCSDK6.3.2 (latest version for all tools)
[TOOL]: MC WB
[DETAILS]: See above.
[EXPECTED BEHAVIOR]: Increase in motor speed
[HOW TO REPRODUCE]: See above.

Best regards.

[Floflo]

Hello Omer,

Are you using rotor sensors and what is the motor connected to your IHM023? What is the DC bus voltage of your system?  (220VAC input -> around 400VDC?) 

The maximum speed may be reached because the maximum phase voltages are output by the system, have you checked the amplitude of the actual signals on the motor phases? Can you monitor the stator current frequency when you increase the speed above 2500 RPM, does it remain stable?

Thanks & B.Rgds

Florent

[Omer Ab]

Thanks to your reply..
We are using a sensorless FOC algorithm. The motor is connected in a delta configuration with the IHM023.

• DC bus voltage of our system: 318VDC

• Input voltage: 220VAC

• Motor parameters: in below image.

Using a voltmeter, we measured the voltage between motor phases A and B, which was 199V.

Additionally, we monitored the motor power using the motor pilot interface. At 2500 RPM, the motor consumes approximately 460W.

Similarly, the rotor current frequency does not increase and remains constant.

NOT : We have delivered the product in its current state, but the customer is requesting a higher motor speed. Additionally, they want to place an order for 1,000 units.
Best Regards...

 

[Omer Ab]

@Floflo  

I have a limited time, we need to go back to the customer, waiting for us..
Can you show how to increase the speed

Best Regards...

[Floflo]

Please check the stator frequency... use a curent probe in 1 motor phase or at least an oscilloscope channel configured in frequency meter. From there you can deduct the frequency you apply in real time to the AC motor (Fstator 'mechanical' = Fstator measured / number of pair poles of your motor). FYI in no load condition you should have a rotor frequency close to the stator frequency (Frotor = Fstator * slip)

Say you have 1 pair pole, if you measure 2500/60 = 41.66 Hz on the stator whatever target you set above the 2500 RPM it means that the FW is clamping the speed to 2500 RPM, so you have to modify your FW in order to generate higher stator frequencies.

B.Rgds/F

[Omer Ab]

Hi @Floflo

I’ve measured the stator signal on the oscilloscope and observed a frequency of approximately 48 Hz.
This corresponds to a theoretical no-load speed of 2880 RPM for a motor with 1 pole pair.

In the ST Motor Pilot, the mechanical speed is 2494 RPM, which suggests a slip of around 13%, typical under load.

However, my speed reference is set to 3990 RPM, which would require a stator frequency of about 66.5 Hz.

Since only 48 Hz is being applied, it appears that the firmware is clamping the output frequency, preventing the motor from reaching the desired RPM.

measured frequency:

 

 

Could you please show me how to modify the firmware to increase the output stator frequency?

However, I would like to point out the following:
I am using the example provided by ST’s Motor Control Workbench in my project, as you can see in the screenshot.
I’ve also made some changes in the speed/frequency configuration settings there, but the motor’s stator frequency still did not change.