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BLDC driver for spindle motor

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radar_macgyver:
I have a 750W BLDC I'd like to use as a spindle motor on my micro-mill. The motor has hall sensors for commutation, but no encoder like a servo motor would have. I tried two different drivers, one rated for 750W, the other for 1 kW, both are no-name Chinese drivers, like the ZM-7206 aka DBLS-08-H-SC

https://www.aliexpress.com/i/33030027300.html

With both drivers, I'm finding that the motor speed is not stable and I can grab the 60mm pulley on the output shaft and stop it by hand especially at lower RPM (drive indicates an overcurrent fault). I'm curious if anyone has had better luck with these, or perhaps documentation showing how to adjust the current limits. There are many adjustable parameters, most of which are not documented. Or do I just have a crappy motor?

thm_w:
Post the information on the motor here, what specs, do we know if it matches the driver.

Drive voltage is stated as 220VAC, are you running off 120V or 220V?
Any chance hall sensors have been messed with, eg not positioned correctly?

http://www.dt-me.com/data/upload/admin/20170323/58d38f0cab215.pdf

radar_macgyver:
It's a no-name motor, the only spec shown is the 750W power rating. It looks very similar to the 80BL150-3130 motor (page 17 in the linked PDF). The motor does not have a data plate. It came as part of a kit with a 110V driver. I suspected the driver was current limiting too early, so I bought a larger driver that is rated for 1 kW, with the same result. The latter driver is operating at 240V (bus voltage of ~370V).

The motor has color-matched phase and hall sensor leads, and the drive has an option to display the hall switching sequence which shows the correct steps when turning the shaft by hand. Wouldn't the motor just not turn at all if the hall sensors were not aligned with the windings?

I first thought the driver is operating in torque mode, but it does have a PI loop (you can program a P and I parameter) and has a programmable acceleration. However, even with a rather high value for the P gain (any higher causes oscillation), the speed regulation is poor under load, I can slow down the motor easily by holding the output shaft.

I don't have much experience with open-loop BLDC drivers (with just hall sensors, no encoder), so I'm wondering if my expectations are too high for this setup. In other words, is it possible to have good speed regulation at low speeds with just a hall sensor?

thm_w:
So the motor was originally used with a 110V driver, now you are trying to use it with a 220V driver. Did you compare the spec of the original 110V driver?


--- Quote from: radar_macgyver on March 29, 2022, 04:37:41 am ---The motor has color-matched phase and hall sensor leads, and the drive has an option to display the hall switching sequence which shows the correct steps when turning the shaft by hand. Wouldn't the motor just not turn at all if the hall sensors were not aligned with the windings?

--- End quote ---

Depends how bad the misalignment is. But if it was a working motor before, and doesn't look like someone messed with it, should be ok now.

Down to 100RPM or so the torque should be OK: https://www.orientalmotor.com/brushless-dc-motors-gear-motors/technology/brushless-dc-motors-servo-motors-inverter.html
You'd normally be running a lot faster than that.

radar_macgyver:
Neither the drives nor the motors came with any useful information, which is why I thought asking here may shed some light on the matter. I realize it sounds like amateur hour, but thanks for answering anyway.

I was able to stall the motor while it ran at about 1500 rpm (verified with a tachometer). It wouldn't run below about 250 rpm.

I'll probably get a DYN4 servo drive and matching motor, those come with decent documentation.

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