Have a Miprom 21 DDC that blows 250a 500v fuses at SCR drive. One time all three legs, one time just L1 & L3. Has happened twice in 6 months. It's in a bank of four. This one car is the only one that does it. thanks for your time dave

-- dave (dac@oz.net), May 16, 2000

Answers

SCR

You must take forward and reverse readings on all scr's and compare to a good scr or another elevator...also if your current limit is incorrectly set, the car can run full speed, even if the brake failed. Over heating the scr's and blowing the amptraps...and by the time you replace them and start trouble shooting, the scr's have cooled down and every thing looks fine...good luck...

-- Joe M... (bachaglupy@aol.com), May 17, 2000.

Also look for loose connections in the ac feeder path for that particular elevator drive. Malfunction or miss-adjustment of motor field controls can also cause excessive motor volts and loss of control of armature current, causing the fuses to blow.

-- Don Vollrath (dvollrath@magnetek.com), May 18, 2000.

Overcurrent

DV@ Magnatec is 100% right....If your field is too.....weak you will get an overcurrent at the hoist motor brushes {arching} creating an overcurrent condition and possibly blowing the amptraps...

Good Luck...Joe...

-- Joe M... (Bachaglupy@aol.com), May 19, 2000.

Miprom 21 AmpTraps

Dave, how old is the Miprom? There has been some bad boards from AB lately. Do they blow at powerup?

Glenn

-- Glenn Schmitz (gschmitz01@earthlink.net), July 03, 2000.

ever check that fan in the bottom of the drive that will do it too

been there done that!!

-- (gipper066@yahoo.com), July 09, 2000.

amptraps

clean out the drive, humidity can cause a scr to ground thru dust. overheating should show a heatsink error

-- cliff smith (cliff77@att.net), October 27, 2001.