Hi,
This old beast from -78 has been working great up until a month ago;
I powered up, hit spindle forward and incresed RPM slowly. Got a field loss alarm, re-booted to try to clear it and got field loss and fuse alarm. Two of the clearup's (thyristor fuses) and two FCF2-20 fuses had popped.
I replaced all fuses and tried again. This time I only got Fuse alarm and only one of the FCF2-20 fuses popped.
I dont have a manual for the drive so dont know what spec resistance is for the SCR thyristors, but at least the individual SCR's dont show open or short.
I have cleaned up the drive and bought a replacement drive control PCB and a Thyristor exciter module, just in case.
I have meggered the motor which is DC shunt type and get 40 - 50 M ohms between armature and frame. On a Fluke DMM I get around 3 Meg ohm between field winding and frame but when meggered at 500VDC I only get 0,03 M ohms. I have not read anywhere what insulation resistance is acceptable for a DC motor field coil, but would suspect this is way too low. Chime in, please?
Now I have pulled the motor off to clean it up and have a closer look inside. I have only pulled apart small permanent magnet DC servos before and this one is 155 kg.
Is there something I should watch out for?
Oh, if anyone has a service manual for Yaskawa Varispeed 505MT or a wiring diagram for Mori Seiki SL3, preferably with Yasnac 2000B control I would be happy to pay for a pdf copy.
Mori and Yaskawa dont have parts or documentation any longer which is very understandable. Many give the advise to scrap the machine, but I really like it:-)
All the best,
Andy