[cnc2]

Hi guys !

I've found a brushless AC servomotor at the scrap yard, I don't know if it's any good, it came without the encoder and I have no way to test it.

Please, advise about testing procedures and how to test run it without a driver board if possible, it has four wires one of which is connected to the housing the other three go to the windings...the only board I have is for a PMDC servo...I have a multimeter and three phase current.

Here are attached the pics of the same motor as mine, look at the name plate.

Here is the link to the manufacturer's datasheet https://blsautomation.com/pdf/Unimot...chure_ver2.pdf

The guy at the scrap yard tested it for less than 20seconds on three phase 380V, the motor started turning and knocking on the ground almost flipping on its side...is that normal ?

Any help/advise is welcome !

Thanks,
cnc2.

[Al_The_Man]

If you have the optional encoder with commutation tracks you can set it up as a BLDC motor, it is actually designed AC sinusoidal.
You cannot run it without a suitable drive that reads the commutation angle.
Depends if you are looking at 10v analogue or step/dir control?
Al.

[cnc2]

Hi Al, thanks for the reply, I've sent you a PM last week but no reply ?

commutation tracks ? commutation angle ? AC sinusoidal ? Can you please, advise a good read to introduce me to these motors ?

I have no encoders except for the AMT102 and an unknown encoder which came on a PMDC brush servo(it seems to be an incremental encoder from the lines on the encoder wheel, BTW this PMDC is also weird because it has four brushes, two on each side and it spins only when the front most set of brushes is connected to a 12v battery) Are these encoders suitable ?

BLAC BLDC what's the difference ? What are the suitable step/dir drives ? What power output ?

Any chance it's been killed by the 380V testing ? any way to know for sure ?

How can I calculate the power rating(KW) of this motor ? what voltage should be supplied (at 3000rpm is it 3x98V)? is it 294V*4.2A for the power?

BTW, the motor shaft doesn't spin freely, it feels like a weak stepper motor with very few steps and when the three leads are shortened it becomes harder to turn the shaft but no steps can be felt, is that normal ? (I know it's not exactly like a stepper I've opened the rear end to take a look at the windings and rotor)

Thanks !
cnc2.

[Al_The_Man]

Hi Al, thanks for the reply, I've sent you a PM last week but no reply ?

cnc2.

I will check my inbasket?

commutation tracks ? commutation angle ? AC sinusoidal ? Can you please, advise a good read to introduce me to these motors ?
!
cnc2.

I will see what I have on file and post it

I have no encoders except for the AMT102 and an unknown encoder which came on a PMDC brush servo(it seems to be an incremental encoder from the lines on the encoder wheel, BTW this PMDC is also weird because it has four brushes, two on each side and it spins only when the front most set of brushes is connected to a 12v battery) Are these encoders suitable ?
.

The motor sounds like it comes with a standard encoder with commutation, you may have to do some reverse engineering if the manual is not avail. These also had absolute encoders which is not good.
The AMT102 encoders will not work without commutation tracks.
Your PMDC motor has a front set, large brushes for power, the other rear 2 will be a tach generator.

BLAC BLDC what's the difference ? What are the suitable step/dir drives ? What power output ?

Any chance it's been killed by the 380V testing ? any way to know for sure ?

How can I calculate the power rating(KW) of this motor ? what voltage should be supplied (at 3000rpm is it 3x98V)? is it 294V*4.2A for the power?

BTW, the motor shaft doesn't spin freely, it feels like a weak stepper motor with very few steps and when the three leads are shortened it becomes harder to turn the shaft but no steps can be felt, is that normal ? (I know it's not exactly like a stepper I've opened the rear end to take a look at the windings and rotor)

Thanks !
cnc2.

AC and BLDC differ mainly in the power to the motor and the commutation.
The motors are basically the same.
You may be able to use Larken or Granite drives?

If it is hard to turn when you short the leads, that is a good sign that the magnets are still OK.
Al.

[cnc2]

Thanks for the reply Al,

I already looked at Granite drives but from what I understood it will not use the motor to its full potential.

Larken ? you mean viper servo drives ? isn't that an HP UHU for brushed PMDC servos ?

The motor sounds like it comes with a standard encoder with commutation, you may have to do some reverse engineering if the manual is not avail. These also had absolute encoders which is not good.

Here is the link to the manufacturer's datasheet https://blsautomation.com/pdf/Unimot...chure_ver2.pdf did you read it ? it says from motor code that this motor had an "Incremental Encoder 4096 C/T" look at page 7 from the manual. BTW the model code is 115UMB300CACAA

Thanks !
cnc2.

[cnc2]

Al,

The motor's manual says you're right about commutation tracks...etc. Here's what it says on page 50:

Commutation
As with commutating brushed dc motors, all brushless ac
permanent magnet motors require commutation information
to enable the drive to synchronise with the rotor of the motor.

Ideally, all feedback devices are aligned with the motor stator
during assembly. For those feedback devices that are not
aligned, the Unidrive has an Encoder Phasing Test (#3.25)
that automatically creates a Phase Position (Phase Offset)
value (#3.28).

Commutation Phase Offset
Most drives, including the Unidrive, provide for a “Phase
Offset” adjustment and a means of setting this to match a
motor with a different commutation setting.
All UM motor feedback devices are set to match the Unidrive
definition of zero offset*1, and similarly DM motor resolvers
are set to match the DigitAx drive, so that the drives may
operate with zero phase offset adjustment, thus allowing
interchange of motors between drives without further
adjustment.
Note that not all drives have the same zero offset definition.
All SL motors have built-in motor map definitions including
commutation information and are fully “plug & play” with
the M’Ax and MultiAx drives.
*1 Earlier motors with incremental encoders require a specific
non-zero phase offset value to be set in Unidrive

OK, now, Any cheap encoders with commutation tracks ? I guess they are required for both AC and BLDC, right?

Thanks !
cnc2.

[Al_The_Man]

BLDC require hall effect or encoder equivalent, AC same, but also use a couple of other methods, resolver or automatic detection from encoder pulses and current.
The motors you have may have the encoder type on them?
I think Granite is capable of auto detection?
Al.

BTW I tried to answer your PM but the response I got was recipient has set not to receive PM's.
I sent a post in the forums to you in this respect.

[cnc2]

BLDC require hall effect or encoder equivalent, AC same, but also use a couple of other methods, resolver or automatic detection from encoder pulses and current.
The motors you have may have the encoder type on them?
I think Granite is capable of auto detection?
Al.

No encoder type is mentioned on the motor's nameplate, the motor code says it had an "4096 ppr (pulses per revolution)- 6 pole; Incremental Encoder" , it came without encoder, but the manual talks about commutation information from the encoder, so I guess it was incremental with commutation signals...I also read this type of encoder has to be mechanically aligned with the poles or a phase offset must be specified...US-Digital has an "equivalent" encoder for $161 with 10mm shaft while my motor's shaft is 15mm

Don't know about Granite, I only know it'll limit the RPM because of the lower voltage.

BTW I tried to answer your PM but the response I got was recipient has set not to receive PM's.

Weird, I've never disabled the feature and checked it right now and PMing is On....Maybe the settings for inbox size have changed ?
here's what I can read about PM status: Inbox contains 6 messages. You have 18 messages stored, of a total 20 allowed. (take a look if you have the privileges)

I sent a post in the forums to you in this respect.

How ? what for ? where am I supposed to receive it ?

Thanks !
cnc2.

[Al_The_Man]

Yes if the encoder is replaced or changed at any time the encoder has to be aligned to the rotor poles.
Here was the post I included the problem with the PM msge.
http://www.cnczone.com/forums/mainte...ml#post1248688
Al.

[cnc2]

I think Granite is capable of auto detection?

From Granite manual "Hall or commutation sensors are not required but are supported for AC/BLDC motors" ...is that what you meant ?

Note: 200 VAC AC servo motors would reach about 40-60% of their rated speed on 160 VDC drive
supply.

Do you know about a better yet affordable alternative ?

Thanks !
cnc2.

[mike_Kilroy]

i have not followed closely so sorry if my reply is off....

u CAN test ANY BLDC or AC servo NO LOAD with any dumb vfd drive and no feedback; it will at least tell if the motor windings are good....

just set accel ramp to like 30 sec to make sure the SYNCHRONOUS motor does not loose syncro....

[cnc2]

Hi Mike, thanks for the reply !

Are you serious ? even if my motor has three wires going to the windings and a fourth going to the housing as GND ? I guess you mean a three phase VFD, right ?

What voltage should I supply ? Any current limiting ? For how long can I safely run it ?

What should happen if the motor is bad ? Any risk to fry the VFD drive ?

I don't own a VFD and have almost zero knowledge about them, but I'll try to look around if I can lend or find a cheap one.

Thanks !
cnc2.

[mike_Kilroy]

i am serious yes

u have a 4amp 230v ac rms motor. u can run it on a std 1hp 230v vfd such as what we sell:

NES1-007SB Inverter, 200-240 volt, 1 phase, 1 HP, 4.0 Amps $212.00


for testing. u cannot generally run a synchronous motor on an open loop vfd for a real world application since if u exceed the torque rating for even a microsecond the motor simply STOP. but easy test to see if a motor is good.

[cnc2]

230V AC RMS ? I thought it was 98V/krpm * 3 = 294V @ 3000RPM ... after looking around the net, Vrms is 294/sqrt(2)=207.9V ....Nice I thought I'd be messing with the three phase and stuff and you put be back on the simpler track, Thanks !

Thanks for the offer, but I am so far that shipping alone would double the price of your VFD, at least now I know that I won't be looking for an expensive high power three phase thing.

Thanks !
cnc2.

[mike_Kilroy]

I did not mean to suggest you buy from me, I was not fishing for a sale, just giving an example for TESTING. Again, a vfd is only for testing - it will not run your motor with a varying load on it - we've tried that in the past and you ALWAYS will exceed the torque it can put on on an openloop controller and it will stall. once stalled only cycling power will bring it back. So ultimately you will need to by a BLDC or AC brushess drive. good luck!

[cnc2]

Mike, I apologize if I sounded like you were fishing after me, I was just trying to be polite it isn't like if you were one of those marketing sharks... You've helped me before and I always appreciate your help.

Thank you guys for sharing your knowledge and taking the time to help me !
cnc2.