# powerflex 70 speed variations



## waterhouse (Oct 26, 2009)

I have 2 powerflex 70(slaves) drives that speed is being driven by the actual speed of a 3rd powerflex 70(master) driven motor. Slave one works as expected. Meanwhile, Slave two is always decelerating and accelerating. Parameters are the same and no product is being used so load is minimal. Leaning towards a mechanical issue but, need to make sure. Any ideas?


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## sparkywannabee (Jan 29, 2013)

surging usually due to tach/encoder if you are using one. If you don't have access to a scope, you can try swapping encoders.


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## JRaef (Mar 23, 2009)

How are the slaves being given their speed commands from the master? Analog output from the master to both slaves? If so, how is that configured, 4-20mA in series, or 0-10VDC in parallel? If you tried 4-20mA in parallel, it would not work that way. If you know you have that right, I would double check your speed signal wire shielding, you might be picking up noise or induced voltages.


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## MDShunk (Jan 7, 2007)

Slap a 22-COMM-(whatever) card in them and call it done. Dead reliable that way. DeviceNet or EtherNet. Whichever is cheaper. 

Curious... how far apart are these drives from each other?


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## MDShunk (Jan 7, 2007)

Just happened to think that it wouldn't hurt to run the autotune routine, just for ****z, to see if that helps any. It's one of the parameters you stick a digit in, then it goes back to normal when the autotune is done.


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## waterhouse (Oct 26, 2009)

Thanks for the responses. it is using a 22com-e card. I swapped encoders as well as installed a new drive. Same issue. I am a shift coverage electrician and only saw this new installation on Friday. I just assumed that the encoder was wired back to the 20A-ENC-1 board on the drive. Not sure if I am right with that assumption. If I am correct I was thinking it could also be a defective 20A-ENC-1 board, connector to encoder not wired correctly, cable issues. I did download parameters from the other slave using the HIM and that made no difference. I did not do an Auto Tune. Is it necessary?

Could you elaborate on the use of the scope? I am an average programmer and a "trying hard to be electrician." Thanks


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## sparkywannabee (Jan 29, 2013)

Signal wires from encoder, A, A not, should be 5V sq wave opposite of each other. If you have a 2 channel oscilloscope, they should be 90 deg apart from B and B not. Check z and z not as well, should be opposite of each other. Tachs are checked for voltage. Make sure you don't have a bad connector, at the encoder itself. I used to have a lot of issues with GE DC250 drives surging, i could change a parameter and the drive would run on CEMF, which i think is like armature feedback, instead of tach feedback. This would really help narrow down, does your drive have anything like that. 
If this system used to work fine at one time, should be something stupid. You'll have it figured out soon. Good luck.:laughing:


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