RUNNING FANUC DC VELOCITY CONTROL UNIT IN OPEN LOOP

[keyancnc]

Hi friends,
can i run Fanuc DC Velocity control unit in Open Loop?
i connected Fanuc Velocity Unit H003 with Servo transformer. i enabled the drive by shorting pin 1 &14, 2 & 15. I put TSA and TSB in open. and VCMD and EC in open. when i give 100V to Drive my Fanuc Yellow cap DC motor is Running at its maximum speed. when Jumper S23(TGLS is disabled)

what my question is , i am not giving Velocity command signal to my drive. why it is running in its maximum speed?

if it is Due to TSA & TSB? or if it is drive problem?

before i handled some AC velocoty control units with RED cap servo motors, but it not having TSA & TSB. so If i Give 100V to enable MCC ,motor OFFSETS and slowly running.

but in DC Velocity control units it is runnig in maximum speed without giving velocity command.

kindly tell me why it is happining.



regards,
keyan

[tc429]

turn the offset pot a little either way...there will be a very tight region where it will stop, but a little either way will equal full speed fwd or backwards. it simply needs a tach input.

pretty sure 6047 dc drives used F/V signal from the cnc (again from quadrature encoder pulse rate) to emulate the tach. Fanucs tach levels are 7v/1000 rpm if you want to fab a tach mount, or build a f/v converter.
I think the big gold axis LSI (7103 chip) used in so many old controls handled the ref, quadrature and f/v signals all on one chip, with just a 455 op amp to boost the analog out... you could probably build a small board using these right off the encoder. find a obsolete r/c robot mother board for cheep and pull the (6) 7103 processors, those are pretty cool chips.

I used a servo as a sub-spindle drive motor years ago and ran into this same dc servo tach issue... found it was just easier to put a 6050 ac servo on (the encoder plugs into the drive- both for commutation and freq/volt tach simulation from quadrature slew rate). a size 20 ac servo works out to about 5 hp IIRC...