Well to eliminate as many parts as quickly as possible I would wire the motor directly to the mainline. Turn her on and see what happens.If the motor still wont turn I would be looking for improper wireing or physical binding.

This is assumming that you have checked your 3 phase power and it is the correct phase and voltage configuration for your motor.But as you say new construction I would be surprised to hear that phaseing was the problem but the wrong voltage is quiet possible.

Yea, a participant! Thanks for checking in. You do understand I'm talking about a problem that has since been fixed, right? It was actually about a year ago. This was an intriguing problem for me, and no one I talked to had ever heard of it happening. A once-in-a-career thing.

I like your train of thought. Yes, I had tried wiring the motor directly to the mainline disconnect. When I turned it on, the fuses in the disconnect blew immediately. The fuses were the correct type for motor rated duty, and the correct amperage, etc, per the NEC. I'll go ahead and tell you that it had nothing to do with the problem. The 3 phase supply in the disconnect was of the proper voltage and phasing. The power supplied was proper in every way, and had nothing to do with the problem. But yes, I sure did a lot of checking on the power, during the course of this issue..lots of head scratching...

Just as an aside, it was interesting that fuses of the same rating DID NOT blow while the power was going through the Seimens solid state starter. Its' current limiting abilities acted like a safety valve. It would allow a certain steady state of current, hundreds of amps even, depending on what allowable percentage of FLA you set in the parameters, but no more than that. But this also had nothing to do with the problem, I thought it was just interesting.

What would you do next?

(oh, boy, got one on the "hook"!) :^)

I probably should mention at this point, that I traced each and every wire, from the T1 terminal on the Seimens starter, to the T1 metal tag on the motor leads, then T2, etc, did each one, one at a time, all were correct. Single voltage motor, 6 leads. At some point, this question will cross anyones' mind, who is wrestling with this issue.

some imperial ac motors were wound to otis spec/labeling. if hooked up incorrectly like it was a nema spec the fields fight each other and create high current and a loud humming. is that the problem?

what about the freq of the motor? was it less than 60hz?

Mr Greenpants got the problem! One of the three fields was fighting the other two. Depending on how the motor last came to rest, it might get hung up in a dither ansd not turn, or it might rotate forward, albeit at high current, with two windings fighting the third backwards one, like two men dragging a third man, hence the great current draw.

The 6 metal "T" numbers were installed in China for Imperial Electric, but not for Otis.

Each of the three windings had a metal NEMA tag installed on each end. And each winding had the correct pair of metal designations on its' leads, but-

On one winding only, the two NEMA metal tags were installed swapped from end to end. The motor was wound correctly, and the windings each had the correct pair of NEMA metal tags crimped onto its leads, but just one winding was labled backwards. So if you wired it according to the drawing, the magnetic force of that one winding ended up bucking the rotor rotation. Two windings made the rotor turn forward, sometimes...Other times it would not turn at all...depending on the exact degree of rotation as the motor last came to rest.

Greenpants, it sounds like Otis had an issue with this before, eh? I had never seen it in my 25 years, neither did the tank manufacturer, nor the Imperial rep. But if they don't get the Chinese up to speed, me thinks they/we will see it more often.

Looks like everything is being made in China now, the default, low-cost labor factory for the world.

sccjr, it was 60hz. Good thought, because if you apply too low a frequency, (or if the motor was designed for a signifigantly higheer frequency) it doesn't create enough impedance to limit the current flow, so there is some validity to that. IDK how far off the rating would have to be to cause a problem, but I dont think the delta from 50 hz to 60 hz would be much of an issue, but Id have to look that up. Aircraft usually use 400 hz transformers, and motors, because due to the greater reactance at the higher frequency, they convert more efficiently, so they can be made smaller and lighter than 60 hz X-frmrs. It was said to me many years ago in aircraft school, if you put 120 vac, 60 hz, onto the primary of a 120vac, 400 hz aircraft transformer, you will draw massive current. (understatement!)

Which makes me wonder, when powering a 60 hz AC motor with a VVVF drive, what limits the current flow at lower frequencies, when the motor is turning slowly? I imagine the currrent sensing coils around the three phase feeders tell the drive board to chop the sine wave earlier and earlier, resulting in less RMS voltage accross what is essentially lower peaks.

I hope everybody found this intriguing! I like to solve and write about stuff like that. And I've got a couple more weird ones, if anybody is interested.

Greenpants has been around the block a couple of times. I first ran into this on a elevonic 401, the ac end of generator burned up and it was rewound. the repair crew hooked up the wiring per the dope sheet only to encounter vics problem. after going through the nema wiring diagrams it became obvious that the windings were not labeled the same as the original otis set up. we just rewired per nema standards and all is well. I have had this problem come around about a half dozen times in the last few years. as soon as you show up on an otis job with rewound ac motor, and they cant get it to run, you will look like a hero when you rewire it to nema standards. this is a good one to remember, as it will happen again.

hey vic, bring on the other wierd ones, im interested 🙂

Scott, I'm amazed it's happened to you at all! I had never seen it, or even heard about it. I thought it might have been a one-off problem.

When I was at Otis, I was compounding the generator on an MRS unit. It was 1990...Gas was a nickle, and dinosaurs ruled the earth..where was I? Oh, yes, for every turn we added in the series field, we should have gotten a linear effect in the base speed, but the speed jumped wildly when adding what should have been just another turn. Sure enough, the series field taps were mis-marked, and there was a couple of markers in the wrong place. I thought it was a neat problem, because the empirical evidence demanded a rational answer, even if that answer contradicted assumed constants. God, I love that sh*t! fun to think about, fun to solve. Sometimes daunting! Gets your brain working! Still hate Sudoku, though.... :^)

Here's one, also on a hydro- The job was a brand new 5 stop, standard bore hole, submersible, Maxton UC5, 60' remote m/r, with an MCE PHC 1000 control. The machine room was hot, because being the Marine Corps, the Feds didn't have to comply with the code mandated temperature maximum. They stuck the tank and control in a boiler room! The Federal Government is exempt from common sense, you know..

Customer would call and say the elevator just wouldn't respond. Everytime I got there, the thing had already cooled down. It kept shutting down on a maximum number of relevels. I forgot what that fault is called, but after 60 relevels, it triggered the MLT shutdown routine. I'd reset the fault, and run it for a bit, but it always ran great, with no problems. Then after I left, it would happen again. Where would you start?

I guess I would first start by making sure the valve would relevel properly, many overload and mlt trips that are intermittent can be solved by making the car relevel and be sure that the car does not overshoot up relevel, or overshoot down relevel, causing a jerking off sequence that eventually trips ol or mlt. Most guys will check this so I don't think it could be this easy. I have had one motion control do what you said and the onlynway we found it after many months of taking guesses was to put a analyzer on the system and check as ,any signals we thought appropriate. After a couple weeks it failed, and we played back the analyzer to find that during the night some one would take the car to the op floor and it would sit there for an hour or so and slowly leak down, and start chattering the Lu signal, this should have releveled the car, but the up normal limit was set incorrectly, and Lu could not move the car up, it would then mlt. Set limit correctly and that was the end of many months of calls. Ok now I'm thinking it can't be that easy, let me think about this awhile .. Ok how about the intrnal motor overload getting to hot and opening, then get a Lu signal and the car won't run up until thermal cools down, then it starts up, but thermal opens again and continues this cycle until mlt