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#7690 - 07/16/13 09:23 PM
Single Speed AC Otis
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Joined: Dec 2009
Posts: 542
solidstate
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addict
Joined: Dec 2009
Posts: 542
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We have been called in on a unit and thought that we had it done. Several companies have looked at this and told them they needed a mod.(a whole different subject please) It is a 1958 circa Single speed AC unit, no selector. It was blowing the mainline fuses when it took off. The problem we thought, and still do,was the brake was not releasing fast enough and the motor was trying to pull through it. You can see the brake pick just a little, the motor hums pretty good and then the brake will pick all the way. We first cleaned all contacts, adjusted the resistors, to get full brake voltage from the rectifier. It worked for about a week and then started blowing the fuses again. We then did a complete brake teardown and adjustment. We pulled apart the brake pistons, cleaned them, turned the sleeve, lubed it with graphite and replaced the coil to be on the safe side. The new coil resistance was the same as the old one. It worked this time for two weeks and today it blew one of the mainline fuses. They are 30 amp, with 25 amp fuses inside the controller. The rectifier was supposedly replaced a couple of years ago. The rectifier while not under a load will produce 160 volts. Once under a load it drops to 127 volts, which we are getting to the coil. It will only blow the fuse at take off, once the brake has lifted it will travel the entire 60 foot of shaft with no problem.
Any ideas?
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#7761 - 07/23/13 02:49 AM
Re: Single Speed AC Otis
[Re: uppo72]
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Joined: Aug 2011
Posts: 563
uppo72
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Joined: Aug 2011
Posts: 563
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#8107 - 08/15/13 01:46 AM
Re: Single Speed AC Otis
[Re: uppo72]
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Joined: Aug 2011
Posts: 563
uppo72
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I would also look at running temporary brake wiring, along the floor away from other wiring, to the brake just in case your getting a leak either thru other cabling(induced ac voltages) or your having a under load break in the wiring so your voltages drop to the coil. I've bumped this up as I think this should be your start maybe after you have tested the motor like JKH just stated. It appears that you have 2 phases shorting or overloading and those 2 are the ones id look at. Also make sure your arc shields are in place as they can track across them.
Last edited by uppo72; 08/15/13 01:50 AM.
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#8189 - 08/20/13 10:47 AM
Re: Single Speed AC Otis
[Re: jkh]
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Joined: Dec 2009
Posts: 542
solidstate
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Joined: Dec 2009
Posts: 542
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It is a three phase unit. Just as it ran for a while after replacing the brake coil and brake tear down. It has ran now for a week without blowing the fuses. It was blowing different fuses in the mainline, not the same ones each time.
We have opened up the motor and looked at it. We have made sure the contacts are even, wipe good, and the shields are in place. Your comment about the material is a likely possibility, did not even consider that.
When we go back out there again, we will look at the contact material, check the amps with a loaded car, and try uppo's suggestion about the brake wires.
Thanks for the follow up.
Last edited by solidstate; 08/20/13 10:49 AM.
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#8206 - 08/21/13 07:02 AM
Re: Single Speed AC Otis
[Re: jkh]
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Joined: Aug 2011
Posts: 563
uppo72
addict
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Joined: Aug 2011
Posts: 563
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Brett I will send you an old print from a tear out. Nothing like a print to refresh your memories. thanks mate.
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#31417 - 07/16/21 03:06 PM
Re: Single Speed AC Otis
[Re: solidstate]
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Joined: Nov 2012
Posts: 7
maine_r
Upsanddowns
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Upsanddowns
Joined: Nov 2012
Posts: 7
New England
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So what was the end result ??
I live in the north east. Where one day you can walk out of the job and it be 60 out and the next day its snowing. good times. Im new to the forum.Iinstall thyssen product and on my way into adjustong. Ive got 15 years in and im 34. UNION STRONG BABY !
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