DRV10983: Ceiling fan speed

Hi Marvin,

Let me review the data and get back to you tomorrow.

Regards,

Vishnu

Hi Vishnu,

Thank you. Please let me know if you need a schematic or other references.

Regards,

Marvin

Hi Marvin,

I reviewed the register settings. The IPD current threshold is set to 2.4A which is high for a 1.8 A rated motor. Can we ask the customer to reduce the current to 1.0 A or 1.2A? And, I'm not sure what they mean by "rotation isn't smoot at startup". Would be great if they can add more details to this by sharing the motor phase current waveform or a short video showing this behavior. 

At maximum speed, if the motor speed fluctuates, we can ask the customer to check the  "Estimated BEMF constant Kt". This can be read through I2C from register address 0x15 and 0x16. If this parameter fluctuates, then the motor speed will also fluctuate. We can ask the customer to tune the Lead time (TCtrlAdv) till the estimated Kt stops fluctuating. More details about lead time in section 8.4.5.7 inDRV10983 Datasheet. 

Regards,

Vishnu

Hi Vishnu,

They tried adjusting the IPD current threshold from 1.0A to 1.2A, but the output remained unchanged. Additionally, the motor rotates only in an open loop,  can you tell me if the DRV10983 will change from an open loop state to a closed loop when it reaches its rated speed or is make a pram change to make the motor operate in a closed loop?

Thanks!

Regards,

Marvin

Hi Marvin, 

Vishnu is OOO today but should be returning next week. 

Please anticipate a response on your comments/questions from him when he is back 

Best Regards, 
Andrew

Marvin,

I'm not sure what the customer means by "Output remains unchanged". During startup, does the fan make noise or move in opposite direction? Motor enters closed loop when the motor speed reaches "open to closed loop threshold". This is configured to 8 Hz so above 8 Hz, motor should start spinning in closed loop. Is there any fault that gets triggered when the motor enters closed loop?   

Regards,

Vishnu

Hi Vishnu,

The problem is still present; we set the IPD current threshold to 1.2A, and the motor started smoothly. However, after a while, if we turned the power off and on again, we saw that the motor started jerking, when it reached 40% of its RPM motor start working fine.

The following parameters were set the EEPROM the chip. 

 Address          Value

0x20         =         0x48 
0x21         =         0x59
0x22         =         0x79
0x23         =         0x4B 
0x24         =         0xC4
0x25         =         0xFE
0x26         =         0x79
0x27         =         0xE9
0x28         =         0x0E
0x29         =         0xFA
0x2A         =         0x5B
0x2B         =         0x0E

Hi Marvin,

Can you check with the customer if the motor was coasting when the power was turned back on? If the motor was coasting at very low speeds, the BEMF will be low and the device will not be able to detect the initial speed. Can you suggest the customer to set the Initial speed detect threshold to 1.6 Hz or 0.8 Hz and try again? 

Regards,

Vishnu  

Hi Vishu,

The customer increased the Initial speed detect threshold from 0.6 Hz to 1.8 Hz, however, the output remained the same.

Marvin,

Was the motor coasting when the power was turned back on? Is there any fault that gets triggered? 

Regards,

Vishnu

Hi Marvin,

Marvn Arcangel said:

24 volts, 1.8 amps, 30 watts, 380 RPM, R ph to ph 2.1 ohms and for phase resistance = 1.05 ohms, and 540 kt

I'm curious that this motor seems to be small/under power for a ceiling fan, and why one wants to run a ceiling fan with 24v DC?

Brian

@Brian Dang - This is a customer in India and ceiling fans in India are usually in the range of 30W-35W and operate at 24V DC. A flyback converter is typically used to convert 240V 50Hz to 24V DC. 

Hi Vishnu, why they don't use small AC induction motors instead? Less flyback converter and no motor driver/FETs/board needed. 

Brian

Brian , AC induction motors are also used in ceiling fans in India. 80% of ceiling fans in India are AC induction. 20% are BLDC.  

Hi Vishnu,

Thank you for waiting. There is no motor coasting when power was turned back on but there are instances that they can see the jerking till the motor reached the min speed (5 to 10 sec), after that its rotate rated speed  

Marvin,

We might see the motor jerking when the open loop current is set high. Can you ask the customer to set the open loop current to 0.8A and try again? 

I've sent you an email. Can you share the contact details of the customer over email?

Regards,

Vishnu

Hi Vishnu,

I saw your email and replied with the customer's contact information.

Thanks for the help.

Regards,

Marvin