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stickman47

Reliance Legacy Drive

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I have a strip accumulator that had two MAxPak III drives running two 40 hp D.C. motors. Last weekend rain water got into one of the drives and it blew up on power-up. The DVDT resistor board was destroyed. We were able to get a replacement board and installed it in the drive. On power-up everything was normal but when commanded to run the display indicared a Current Minor Loop Fault and the drive shut down. I was troubleshooting this when my superior calimes that the blower motor was single phasing and pulling down the line. I checked the blower motor and found only that the starter overload block was faulty. I eliminated the overload and the blower ran fine. We pulled the drive and sent it out to Radwell to be checked out. The drive returned within 6 hours and they said they replaced a faulty "Output Module". I re-installed the drive and powered it up, all was well. Whe I commanded the drive it blew out one of the transistor modules and two of the line fuses. Since we could not get this problem repaired the decision was made to replace the drives with new Seimens drives. This was completed this weekend and on power-up the blower motor went up in smoke. My superior is claiming that this was the problem all along and that there was nothing wrong with the MaxPak III from the begining. I can't defend this position but I feel the two could not be related. Can anyone help me here? I think this could mean my job if I can't come up with a reasonable explanation as to why the blower could not have caused a Current Minor Loop Fault in the drive and I can't find any information on the MaxPak III ANYWHERE!! HELP!!!

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Stickman - I am assuming that the blower motors that you refer to are the blowers that circulate air through the 40 HP DC motor. I also assume that the blower motor is a fractional HP, 3 PH, AC motor with a separate across the line start (independent from the DC Drive). "...the display indicared a Current Minor Loop Fault and the drive shut down." Is there a CT loop on one of the blower motor leads that feeds back to the DC drive? Is there an auxiliary contact on the blower starter that connects to an input on the DC Drive? If so, that could be the relation between the blower and the DC drive and the minor current loop trip. "I checked the blower motor and found only that the starter overload block was faulty. I eliminated the overload and the blower ran fine. " Did you eliminate the overload protection, as is it's no longer in the motor circuit, or did you replace a bad overload relay or set of thermals? If so, was the unit set to the correct motor FLA? "This was completed this weekend and on power-up the blower motor went up in smoke." There was probably an original condition that caused the OL's to trip... Did you do any diagnostic testing to the motor (resistance measurement across the windings, meg windings to ground, check the across the line voltages, and get running current readings on all three legs)? You mentioned rain water leaks... Did the motors, specifically the blower motor, get wet?

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JMK, You are correct that the Blower was the cooling motor mounted on the 40 HP motor. It was connected through a "Blower Motor Kit" mounted on the drive. It had a connection on the overload block aux. contact that was wired to the machine e-stop. When the overload was eliminated the motor ran fine and had not indication of any problem. No rain water entered motor, but there was substantial water in the maxPak III dirve unit that caused the failure of the DVDT board. There was no deteoration of the line voltage with the blower running. the only message we got was "Currnet Minor Loop Fault". The drive was putting out voltage for a second before the fault shut down the DC contactor. We also read a high current on our scope at the test points indicated in the manual. I feel that three was damage to one of the SCR modules when the DVDT board failed and this was the cause of the drive failure, not the blower motor. Stickman47

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I know it's a bit late, but here's a link to the MaxPak III books... Replacing one drive with another manufacturer's can be tricky, so I'm not totally surprised at the blower motor going. I just crossed my fingers last Thursday when I replaced an EMS drive with a Control Techniques drive. Start-up went ok on 1st shift, but 2nd shift didn't tell 3rd shift about the change so they had a couple of crashes while starting the line because they set the speed pot at the old setting. Fortunately, no one blew up anything! Good luck coming up with the explanation.

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ssommers, Thanks for the link. I had seen those publications and they were not of any help, too specific. I found the problem with teh blower motor, bad wiring to the motor. As for the drive failure, after the water damage was repaired and we could not get the MaxPak III working we swaped out with Seimens. The conversion went o.k except for the motor encoders. The Seimens unit would not work with the pulse encoders so we improvised until a decoder card arrives. During the start-up we discovered that the original current minor loop fault was caused by a defective isolation transformer on the line. The new drives also indicated a problem that led us to find this transformer problem. The boss is upset about this but I explained to hin that you can't keep running obsolete equipment forever, eve if you have spares. Eventually there will be no one to repair them or advise us when there is a problem. Theses drives were 18 years old and Reliance just doesn't exist anymore. Even my old Reliance service contacts were retired or dead. It's a tough pill to swalow but when you wait too long to upgrade this is what you end up with. The machine is now running, although still limping. but I hope to have everything resolved by week's end. Thanks to all for your help, it looks like I can keep my job...

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Too late to help, but just wanted to reaffirm for you: There is absolutely no way that the blower motor problem caused the current minor loop fault. There is no legitimate reason for you to receive blame because a wet drive ended up dying, unless you are responsible for roof repairs, or whatever problem allowed the drive to get soaked. A panel full of water is alomst always going to cause more than one failure, and it may take some time to find them all and fix them. You can try to get everything dry and test the big stuff, but at some point you have to cross your fingers and throw the juice to it and see what smokes. I have dealt with lots of flooded panels, and it is never easy or simple, so I feel your pain. Good luck, and hopefully the boss will eventually realize you probably saved them from other costs by being able to troubleshoot properly and for the emergency retrofit...

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OK, let me get this straight. You have an old Maxpak III. You can obviously tell by the ummm....interesting "display" module how old it is. It has a blower motor hooked into the drive with an overload to protect the drive circuitry in case the fan motor does something bad (or the fan gets jammed). And you simply bypassed the overload? You didn't even try to scavenge one out of an old starter? Since you eliminated any and all protection, how could you determine that the fan motor didn't cause a problem? Have you ever fought with a bad inertial switch? Meggering a motor catches about 90% of motor faults. It doesn't catch 10%. I have a Maxpak III this week where the fan motor was running right at FLA. Meggering doesn't show anything. What was wrong? Turned out it was a loose & corroded terminal. This did NOT show up by meggering. A voltmeter found the problem. What would you say if it was a phase imbalance problem?

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