Delta vfd error codes

[Tmag8500]

Hey guys and gals, I'm having some trouble with a CS350 cold saw with a Delta VFD model 022E21A. Yesterday it would power up and run but wouldn't get to the full rpm. It is a variable speed machine with up to 120 rpms but was only getting to around 40. Today I'm getting an error code ( AErr) which is an analog signal error. The fix for it says check wiring of ACI. Any idea where to start? VFDs are new to me but always willing to learn. I've tried looking for Youtube videos but can't seem to find what I'm looking for yet. The saw has been sitting awhile and unknown if it ever came up to full speed.
Thanks in advance.

 

[mksj]

A common problem is the speed pot becomes erratic, has a bad connection or the trace (resistance path) has deteriorated. I would remove the speed pot. and check its continuity/resistance with an ohm meter. It should read 5K Ohm between the high (3) and low terminals (1) and via the center sweep (2) it should be a linear increase/decrease when measured between the center sweep (AVI) input and either the high (+10V) or low terminal (ACM). Check that the connections to the VFD terminals are secure. Another option to test the full speed only would be to remove the speed pot wires to the terminals and connecting a wire jumper from AVI to +10V and this should give you full speed. It the poteniometer is bad, you can replace it with a linear 5K ohm with a 2-4W rating. These are readily available through electronic distributors or eBay.

 

[brino]

Wow, the only thing I could possibly add to Mark's excellent reply is:

Use a linear ohm meter (meter with needle) for checking the potentiometer, with a digital one it can be difficult to see any issues due to the digits bobbling around.

-brino

 

[Tmag8500]

Thank you for the quick responses. I'll check the potentiometer out and let you know. Thanks again.