erratic spindle speeds Askpower inverter series a131 (SOLVED)

[springlakecnc]

I have a rev2 Acorn and we added the relay board. We have 3 of the " Askpower inverter series a131" that look like a Hunyan frequency drive and are sold on e bay, the spindle speeds are erratic on all 3. when i switch from fwd to rev, the analog voltage drops 2 volts and varies up and down 1 volt. We used shielded cable. The Askpower only has 1 "ground" hook up and shows the analog 0v going to it AND it also wants you to run another wire from it going through acorn relay start forward back to Askpower start forward and same with start reverse.

I took Acorns 2 analog wires out of the inverter, put my meter on them, right by the inverter, and they were rock steady. Switching to reverse, i got the exact same volts and steady also.

I then changed command back to the panel on the inverter, and it ran great. steady, same speeds in reverse, etc..

I don't like the idea of the analog not having 2 inputs and sharing the ground, but i'm not an electrical engineer

Any ideas?

[martyscncgarage]

I have a rev2 Acorn and we added the relay board. We have 3 of the " Askpower inverter series a131" that look like a Hunyan frequency drive and are sold on e bay, the spindle speeds are erratic on all 3. when i switch from fwd to rev, the analog voltage drops 2 volts and varies up and down 1 volt. We used shielded cable. The Askpower only has 1 "ground" hook up and shows the analog 0v going to it AND it also wants you to run another wire from it going through acorn relay start forward back to Askpower start forward and same with start reverse.

I took Acorns 2 analog wires out of the inverter, put my meter on them, right by the inverter, and they were rock steady. Switching to reverse, i got the exact same volts and steady also.

I then changed command back to the panel on the inverter, and it ran great. steady, same speeds in reverse, etc..

I don't like the idea of the analog not having 2 inputs and sharing the ground, but i'm not an electrical engineer

Any ideas?

First, disconnect the spindle Analog ouput wires AT Acorn
Connect a DC volt meter directly to those Acorn terminals.

Go into the wizard and for spindle speed set 0 for low RPM and 1000 for High Rpm
Save

Go to MDI and Command the following and see if you get the resulting values
M3 S100 = 1 Volt
M3 S200 = 2 Volts
M3 S300 = 3 Volts
M3 S400 = 4 Volts
M3 S500 = 5 Volts
M3 S600 = 6 Volts
M3 S700 = 7 Volts
M3 S800 = 8 Volts
M3 S900 = 9 Volts
M3 S1000 = 10 Volts

If the above are ok, then reconnect your wires, disconnect from your VFD and repeat the test?
OK or NO?

If OK,
Reconnect your VFD and rerun the test monitoring the wires connected at the VFD
Result?

You say you used shield cable. Did you ground the shield on one end, both ends or neither?
Try and disconnect the shield and rerun the last test (wires connected to VFD and monitoring the voltage at the VFD)

Marty

[springlakecnc]

SOLVED !!!

Hi Marty, and thanks for the response. I have installed hundreds of frequency drives, this is the only one i ever seen with only 1 common/ground on the inputs.

Attached is how i rewired it and it works perfect. you may want to check this out because e bay is selling these cheap, and I'm sure someone else is going to have this problem.

Thanks again,
Bill

inv .pdf

(2.38 MiB) Downloaded 142 times

[martyscncgarage]

Thanks for letting us know and for posting the connection diagram.
It would be helpful if you posted the parameters you changed also for that particular drive so other users can have it for reference.

Marty

[kwkenyon]

Marty,

You mentioned the analog voltage check using 1000 rpm. Each 100 rpm 1 volt. What if that is not the case, say less than or more than 1 volt? Is there a way to correct this in ACORN? Thank you.

[martyscncgarage]

Marty,

You mentioned the analog voltage check using 1000 rpm. Each 100 rpm 1 volt. What if that is not the case, say less than or more than 1 volt? Is there a way to correct this in ACORN? Thank you.

No. If it's a little off that's normal and nothing to worry about. Post your results of the test. Have no idea what you got.

[kwkenyon]

For Info:
My analog wires are all properly shielded. The results of my test are as follows: 0 RPM = 0.195V, 100 rpm = 1.195 Volts, 200 rpm = 2.196 Volts etc. All the way up ca. 0.195V +- a couple mV. I've worked with Stephen at DMM and I can set the deadzone in the servo to keep it from rotating at Acorn power up. The draw back is Acorn still sees this .195mV and when the M3/M4 are called it sets a rpm exactly minus the maxspeed setting of the servo because of this Acorn drift voltage. If the analog output was in fact 0V there would be no problem. Hence my question if it was possible to Adjust Acorns analog output through the parameters. Possibly A/C servos are to sensitive to this drift and a VFD is no problem? I found it an interesting project to use a Servo as a spindle. Maybe not?

Thank you for all your help and time.

[martyscncgarage]

For Info:
My analog wires are all properly shielded. The results of my test are as follows: 0 RPM = 0.195V, 100 rpm = 1.195 Volts, 200 rpm = 2.196 Volts etc. All the way up ca. 0.195V +- a couple mV. I've worked with Stephen at DMM and I can set the deadzone in the servo to keep it from rotating at Acorn power up. The draw back is Acorn still sees this .195mV and when the M3/M4 are called it sets a rpm exactly minus the maxspeed setting of the servo because of this Acorn drift voltage. If the analog output was in fact 0V there would be no problem. Hence my question if it was possible to Adjust Acorns analog output through the parameters. Possibly A/C servos are to sensitive to this drift and a VFD is no problem? I found it an interesting project to use a Servo as a spindle. Maybe not?

Thank you for all your help and time.

Did you do the test with NOTHING but the meter connected to Acorn spindle analog output?
Acorn's analog voltage can not be adjusted.
Acorn was never inteneded to drive a servo motor.
I am currently testing DMM's DYN4 as a Spindle motor.

The issues as observed them as of this morning:
1) DYN4 needs an input for FORWARD and an input for REVERSE. DYN4 would then NOT rotate unless one of the inputs was called.
(Just like a VFD)
2) You CAN NOT stop the servo motor when its running at a high speed. (Call an M5) DYN4 will fault. There has to be a place for that energy to go. A VFD uses a braking resistor and has Accelleration and Decelleration settings.
3) DMMDRV does not have good way to set Accelleration and Decelleration settings. Try and rigid tap....
4) DMMDRV makes you jump through algebraic equations to come up with some of the settings. Quite simply they need an Accelleration and Decelleration field in the DMMDRV software that you enter seconds into.
5) PID Settings may need to be tweaked.
6) Motor speed is not exactly tracking with commanded speed. I have noted my spindle exhibiting a "quivering" behavior. What it appears to be doing is dithering between encoder marks. I have gotten this to get better by increasing the MAX GAIN in DMMDRV.

DYN4 and an AC Servo was designed to be a SERVO motor, NOT a spindle motor. I don't understand the infatuation with trying to use it as a spindle motor. Are you folks trying to do this simply trying to kill mulitple birds with one stone? I.E. a spindle motor (which MUST be belted to the spindle at 1:1 by means of a timng belt). And because there is an encoder output on DYN4, you are connecting it to Acorn's Encoder input, so you don't have install an encoder on the spindle? Lastly some of you are infatuated with trying to make your lathe have the motor double as a positional C axis.
You understand that you are asking the servo motor to hold position against tool cutting pressures? Drive can fault during such an operation, freeing the spindle and could lead to something ugly.....

While I give DMM credit for trying YOU guys need to understand their DYN4 and AC Servos were never designed to be spindle motors. They were designed to be servo motors.

VFD, 3 phase motor, line driver differential encoder mounted at 1:1 to the spindle is proven and the way to go. Everything else is just an experiment at this point.

My .02 on this issue, if anyone else has successfully made it work, share your recipie. (Keep in mind I am doing some testing on an EMCO PC 5 lathe, and testing the DYN4 and AC Servo as BOTH a Position (C Axis) and Spindle motor. I have NO interest in either other than many of you are attempting this. I will stick to VFD's and encoders.

Marty

[kwkenyon]

Great Marty, thanks for you viewpoint. I have already rigid tapped and cut steel. I only wanted to know if i could get the M3/4 speeds corrected. I got it thanks. I'll post once finished. Appreciate your input.

[martyscncgarage]

Great Marty, thanks for you viewpoint. I have already rigid tapped and cut steel. I only wanted to know if i could get the M3/4 speeds corrected. I got it thanks. I'll post once finished. Appreciate your input.

Love to see a video, with your setup and it rigid tapping, and see/hear your recipie for setting it all up....
The abrupt start and stop of the servo is not having any effect on your tapping? What size taps are you running?

Marty