Nuisance tripping of 80 amp CB?

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Mustangx3

Member
Location
Global
Hey out there... here's what we have. A Siemens ED63B080 80 amp 3 phase CB is tripping randomly when our elevator pump motor starts up. The motor is a 40hp 3 phase motor by Magnetek. Pretty normal setup and has been reliable for many years. What we see is when the contactors shift from start contactor to run contactor the incoming power wires "jump" (sort of like stiffening up). The amps are about 130 amps start and 50 amps run. Motor has been completely checked without finding problems, new contactors have been installed, new circuit breakers and even the wires have been upgraded to 6 awg from 8 awg.
Sooooo, what would cause an 80 amp CB that is supposed to trip at 25k amps/480 randomly trip when this motor switches from start to run?
We did a check on the building power with a Powersight 3000 unit and found that the building power rises and falls from typically 460 vac to 510 vac over a 3 hour period. We have seen sags down to 330 vac and peaks at 510 vac (phase to phase). The sags seem to happen on all phases at random times (about every 45 minutes one of the phases will sag). We also see current on leg A is below B and C legs (example, when the large air comp. kicks in we see 210 amps on B and C legs but only 110 amps on A leg). The A leg seems to always be 10 to 100 amps lower than the other legs. The "high voltage" guys say nothings wrong with building power and that it's the elevator... see our problem? Any extra "2 cents" out there would be appreciated!
 

69boss302

Senior Member
Re: Nuisance tripping of 80 amp CB?

I have had about three instances similar to this. All three times it took some doing but we managed to find a wire chaffed or exposed somewhere inside the conduit or wireway and grounding out intermittently. A 150 HP nitrogen compressor motor, a 250 HP DC motor, and a 40 HP hydraulic pump motor. If your wires are moving then it's usually a sign of an excessive load somewhere. Only other place I've actually seen wires move that much is feeders to an electric arc furnace, and that's the way you can tell if they're working right.

Have you meggered everything. The ones I have seen were intermittent and very hard to find. One even found us instead of us finding it. Smoke can give you a good indication of where there is a problem. Not exactly a recommended troubleshooting practice however.

Welcome to the forum MustangX3 careful it's addicting :D
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Re: Nuisance tripping of 80 amp CB?

What we see is when the contactors shift from start contactor to run contactor the incoming power wires "jump" (sort of like stiffening up).
If one of the contactors is hanging up, on transfer, there is a possibility of excessive current. Also the trip of the 80 amp breaker should be no where near 25,000 amps. I would expect to see the instantaneous trip point of this breaker to be in the range of 1200 to 1500 amps.
Don
 

69boss302

Senior Member
Re: Nuisance tripping of 80 amp CB?

True don, I believe the 25,000 would be referring to interrupting capability, not where the breaker trips.
 

brian john

Senior Member
Location
Leesburg, VA
Re: Nuisance tripping of 80 amp CB?

1. Check the transition timing, from start to run this can be done with the motor disconnected and only control power on, if it is an open transition, a light bulb set up through both starters should do it, if it is a closed transition time the closed transition, with a stop watch against what the manufacture recommends.
2. Megger the cables, cables that snap on start up are not uncommon, pretty standard actually for large motors, the snap as noted can result in insulation failure over time.
3. High current test the circuit breaker, long time at 300% instantaneous at pick-up typically 4-12 times depending on the manufacture, curves are available for CB?s
4. This CB is not that expensive replace it and if it still happens see above 1-3.
 

charlie tuna

Senior Member
Location
Florida
Re: Nuisance tripping of 80 amp CB?

hydraulic elevator motors have a reputation for inducing very high starting current due to the motor starting under full load conditions. i have seen many times where feeder breakers needed to be replaced every couple of years. especially, if the current rating of the breaker is close to the current drawn on start! they also have a high problem rating concerning connection problems due to these surges ---check all your connections too!
 

Mustangx3

Member
Location
Global
Re: Nuisance tripping of 80 amp CB?

This is sort of why I was even writing in the forum (everything's new). Although everything meggered OK, etc. The building officer wanted parts changed. We ran all new wire from the main dist. panel to the motor, there are new oversized contactors installed and the CB's are also new. Basically the entire system from the street is new wire, breakers, contactors, motor, etc. The mfg. states a 1.4 sec. start/run transision and it's right on 1.4 sec. The system has been working great for years but they recently had a lot of electrical work done in the building. This elevator starts without a hydraulic load. The way it works is the motor starts up (wye) while the hyd. valve is in recirc. mode so the oil just recirc. in the system. Once the motor goes to run(delta) in 1.4 seconds, the hyd. valve slowly switches from recirc. to "up" which begins moving the elevator up. As the car nears the floor landing, the hyd. valve slowly moves back to recirc. to slow the car down and have it level off at the floor landing. Motor current start up is about 130 amps and running current is 50 amps. We are suspect of building power since the 480 vac sags to 330 vac every 45 min. or so for some unknown reason.

Oh, and the rating was for interrupting capability.

And we are still tripping (trapping the riders for a few minutes till we reset it).

Arghhhh!!
 

69boss302

Senior Member
Re: Nuisance tripping of 80 amp CB?

Mustangx3, this could sound like the typical electrical/mechanical battle, but, is the hydraulic system functioning correctly? Is the pump binding. Doesn't sound like it if your current draws are checking out correctly.

Does it trip always at a certain time?

Does it run a fixed amount of time each time?

Does it trip with the elevator at the same spot every time?

Your voltage sag could definitely cause a problem also depending on when it was during the start cycle. Do you have any thermography program for your distribution equipment?

I know these are just a bunch more questions that may have been asked already but may need to think of it from another angle.
 

Mustangx3

Member
Location
Global
Re: Nuisance tripping of 80 amp CB?

Yup, hydraulic system is fine. Can even take the belts off the pump and run the motor alone with tripping still (go figure that one).
Trips are at random times, nothing we can re-create either. "usually" trips when transfering from start to run (or a second or two after run contactor pulls in). The run time varies also, once we saw the chart recorder show that the motor went from start to run but tripped even before the full 50 amp run draw was there (about 35 amp trip, motor never made it to "run"). We thermo. the whole system, connections and all without any problems noted (cool running). Contactor pads are clean with minimal arcing wear (new 3 weeks ago anyway). No signs of ANYTHING wrong except building power sagging (510 vac to 330 vac) and an uneven amp load on the building (A is up to 100 amps lower than B or C legs). Keep on with questions, that's where we are at now... what angle can we head to find the "smoking gun". Kinda kicking our butts since everything has been changed out with new and we think we've eliminated any possible causes except for building power concerns.
 

69boss302

Senior Member
Re: Nuisance tripping of 80 amp CB?

If your using a chart recorder you may not be picking up any quick transients in the system. Do you have an actual portable power analyzer to hook up to it. There's some good one's you can rent or maybe your power company or a local motor shop that also does power analysis can help you out. Sure sounds like something funny with the power. Definitely an electrical problem though.

May sound silly, but is there anyway to run power to it from another source, separate panel or anything?
 

Mustangx3

Member
Location
Global
Re: Nuisance tripping of 80 amp CB?

We have the chart recorder and a Powersight 3000 monitoring it. The powersight is what has been picking up the transient events (pretty neat unit) such as millisecond sags and spikes, etc. The high voltage people don't seem concerned with a nominal 480 vac system running between 510-330 or the unbalanced amp draws on the 3 legs. I guess it is possible to get power from another main switch panel but that would be a whole bunch of work. We have been monitoring upstream at different spots and the same building power concerns are there too. The only spot we haven't been able to get someone to monitor is upstream of the main transformer. The "powers that be" say it's the elevator (ignore the fact that everything is new, upgraded, oversized, and that it just started happening AFTER all the building electrical work was done...). I figured (although nothing checked bad) we would be forced to change things out (CB's, contactors, motor, connectors, and even the wire itself upgraded from 8 to 6) and once all that was done they would believe it's not the elevator since everything was new but that didn't appear to convince anyone. I've asked what do they want us to change next but they know there is nothing else to "easter egg". It boils down to what in the world could cause random tripping when we know that we are not getting high amps (unit also has overloads on the contactors that doesn't trip). My theory is that if the elevator gets a call and the motor starts at the same time there is only 330 vac on one leg it would act like a single-phase to the motor.
 

69boss302

Senior Member
Re: Nuisance tripping of 80 amp CB?

Well not like a single phase, but amperage draw would be much more and speed would not come up as fast so that when it did go to swap to run the speed is still possibly bellow the pull out torque portion of the curve and could give you one heck of a jump in current, but that should show up on your power monitor. I wouldn't be concerned about the 510 Volts (after all that's what our friends to the North use) but I would be very concerned with the 330. If they just did a bunch of building electrical work I would definitely suspect that, more than likely some loose connection somewhere. Problem is finding it. Not a good plan to let it find you, usually other things start blowing first.

I think the Easter bunny may of done a real good job in hiding that egg. I can remember one problem kind of similar also that took us about a month to find. Found a building joist support that had fallen onto one of the ariels (that's old stuff for most of you), and welded itself to the building and ariel. It was up in a dark corner so no one could find it for a while. We were having all sorts of problems, one guy just noticed a red glow one night where there shouldn't be a red glow. Don't want to discourage you but just keep your eye's and ears open.

You said you had a big indication with an air compressor starting also?

Is that on the same feed? or panel?

Do you have any way to isolate area's of the power supply while the elevator is working?

Another couple silly questions, and probably can't be done if your in one building. I'm not familiar with your set up. I have done that before though, dropped parts of the plant so we can run the other piece of equipment to see if it would run OK.
 

Mustangx3

Member
Location
Global
Re: Nuisance tripping of 80 amp CB?

Yeah, when the air comp. starts up the amps are way unbalanced.
A=110 amp
B=210 amp
C=210 amp

All those items come off the same 800 amp panel and it takes an act of Congress to even think about isolating other parts of the building to troubleshoot. Another thing... I'm thinking something is causing that sag to 330 vac is upstream because we don't see the amps go up when the volts go down from where we are monitoring. We see the volts sag to 330 vac but the amps stays roughly the same. Does that seem correct thinking?
 

69boss302

Senior Member
Re: Nuisance tripping of 80 amp CB?

Did you say they did some work on the building power. What all did they do?

I can't understand why they wouldn't be concerned with voltage sags to 330 volts. That's close to a 30% sag.

Do the lights blink or dim by anychance?
 

charlie tuna

Senior Member
Location
Florida
Re: Nuisance tripping of 80 amp CB?

mustang,
330 volts represents a 30 per cent voltage drop.
a ball park figure on a motor load is if you lower the voltage by ten per cent it will near double the current draw. and can you imagine the damage to other equipment. why was the system changed? what did they add? have you actually changed the tripping breaker. we recently had a similar problem on an 800 amp westinghouse breaker feeding an elevator machine room with six cable cars. our data logger showed it tripping at only eighty amps and never really was loaded more than 140 amps. we tried changing the trip element and when the tripping continued we replaced the breaker. i would record the voltage at the main service to see if that sag is being caused by another building? power company specs usually require (+)or (-) ten per cent. they may be running on an alternate feeder or something---you don't think they are going to tell you---do you? your recorded information should show the voltage at the trip point--is it during the sag??
 

Mustangx3

Member
Location
Global
Re: Nuisance tripping of 80 amp CB?

Several companies have done power work on the building systems but no one can tell us "the big picture" of what all was done (go figure). There hasn't been any blinking lights or dimming that we are told, quite a bit of the systems are on huge UPS too. The building was being upgraded for more large equipment coming in (and some 400hz stuff). Everything in our elevator system was changed out (see above posts for details). We can't re-create the trips but haven't been able to positively say the trips happened exactly when the sag is occurring. We just keep monitoring and brainstorming. Frustrating!
 

Mustangx3

Member
Location
Global
Re: Nuisance tripping of 80 amp CB?

The UPS just show power sags are occurring. 3 "suits" showed up today with expensive laptops... they appear to be ready to help on this issue so MAYBE these men in black will have an extra 2 cents to throw in. I'll post what happens...
 

catchtwentytwo

Senior Member
Re: Nuisance tripping of 80 amp CB?

The reason I asked if the UPS's see the event is that if they "go on battery" often due to it, the batteries are taking a major beating. Especially if they are sealed VRLA (Valve Regulated Lead Acid Batteries). No matter what battery type, each "on battery" event takes some life away.

If you need a justification to do more involved troubleshooting or a shutdown, mention this to the IT people.
 

Mustangx3

Member
Location
Global
Re: Nuisance tripping of 80 amp CB?

"The Dream Team" looked at all the data and came up with nothing yet. I love it, the MIB got the butts kicked by this too. That's 9 electricians, 3 engineers and a couple old elevator mechanics all scratching their heads. Has been making for some interesting conversations though...

Any other thoughts please post!
 
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