Soft start motor control?

hot_rod

We have this soft start on our irrigation pump, 30 HP, 480V 3 phase. We replaced the motor, and an electrician wired it, checked rotation with just a bump as we hadn't flooded the ditch yet to run the pump.

When I try to fire it up now I get the "phase loss" error. All legs measure 485 V.

Any motor control guys out there?

Solid_Fuel_Man

You have all 3 phases there? 277 to ground on each, and 480 line to line on all 3? 

Have you checked the resistance of the 3 motor leads at the soft start? Should be around 5 ohms for a 30HP motor. 

hot_rod

yes on the 3 phases, I will check resistance, thanks.

The electrician did switch two legs to correct rotation, would that confuse the starter?

Zman

Did you verify that all the leads are wired correctly for 480?

Solid_Fuel_Man

Moving phases for correct rotation shouldn't have anything to do with the control throwing a code for phase loss. 

I'd also try unwiring the motor side and do a start with no load. See what code the soft start throws then. 

Any chance you can put a meter on each phase during a start? Of do it 3 times to be sure that phase isn't disappearing under load. 

hot_rod

I’ll try removing the drive, disconnect the motor from the pump shaft also, that is how it was run and tested for rotation, under no load.  I can spin the pump by hand, so it should start.

Zman

I have seen the symptoms you are seeing caused by incorrect, loose, or fried wires under the cover on the motor where the leads come together. It was causing a similar message on the VFD and one phase was dropping out on amps.

hot_rod

so testing testing each leg to ground I get
242v, 242v and 422v on one leg

with pump feeds disconnected it trip phase loss error right away, still

Jamie Hall

All three phases should be exactly the same (assuming no or very little load) to ground or neutral. 3 phase Y should be 277 phase to ground (or neutral) and 480 phase to phase or sometimes 208 phase to phase and 120 phase to ground (or neutral). Somethings not right in the wiring...

hot_rod

It must be a power company fault then, this is measured right at the breaker panel.

JakeCK

hot_rod said:

It must be a power company fault then, this is measured right at the breaker panel.

Don't you just love it when the poco delivers dirty power? I fought that battle at my house years ago for months. They kept saying the problem must be in my house. That is until whatever was wrong out on the pole blew up and knocked out the whole neighborhood. Then no more problems at least for a long while... I guess it wasn't my house. The whole battle is why every sensitive piece of equipment I own that can be on a UPS is on a UPS. 

I wish you luck dealing with the power co.

hot_rod

this is in the middle of a farm field, along an irrigation stream, so the transformer on the pole is only for our pump.

hot_rod

isn’t there a 3 phase high leg power? Where one leg reads the high voltage to ground and the other two read the lower voltage of a 277/ 460 service?

Jamie Hall

Hmm... well, there is a rather unusual three phase wiring called high leg delta which will give that voltage ratio for the phases to ground. It uses a centre tap on one leg of the secondary of the transformer and connects to neutral there. The transformer is usually set to 240 volts, give or take, phase to phase, and two of the terminals give 120 to ground. In your case it could be 480 phase to phase, which would give the voltages you measured to ground.

NOT a very common arrangement... Older installation, maybe?

MikeAmann

Any phase to NEUTRAL = 277v
Any phase to another phase = 480v

MikeAmann

Your 3-phase high leg delta is here: https://pveducation.com/solar-concepts/common-electrical-services/

JDHW

A few pictures of the pole from different angles with a telephoto lens would maybe help deciding the supply you have.

ScottSecor

I believe they refer to your incoming power as "red leg" here in my area. Not too common here, but I have seen it on a few occasions.

I doubt this is helpful and my memory is a little fuzzy about this job from over twenty years ago. We installed two large dual fuel power burners at a private high school campus, one for each of the dorms. We were aware that this was a "red leg" power supply. From day one we had nuisance lockouts at each building. Sometimes the lockouts would occur two or three times per day. The campus administration pushed the utility company hard for months to rectify the power issues and they denied it was there problem. Only these two buildings were fed with this above ground transformer. The feed to the transformer was underground, so were the feeders to the buildings. When they decided to replace the boilers after one season, we re-purposed the burners (as planned) and installed them in the new boilers over the summer. During the summer, the gas company ran new gas lines to the buildings and accidentally ripped the underground wires feed out of the boiler room panels (yes ripped them out). The utility company fixed everything and got the power up again. A few weeks later, the utility co. reluctantly decided to replace the transformer. That was the end of the nuisance lockouts.

clammy

We have the red leg in my area ,it’s the end of the service line for one utility company and the end of another . Usually w a motor starter I like to install a phase monitor just to protect things,better to protect then replace I feel . As other have stated I would go over the motor wiring closely to ensure it s bugged properly for you voltage on more then a few occasion I ve had electricians ,plumbers and other Hvac techs wire multi voltage 3 phase motor incorrectly ,worse is when they burn them out . I kinda remember having the hot leg specify wired to one leg of the unit . These where package rooftops and this was many many years ago . You could also ohm out the motor wirings and check against motor specs . A phase ,voltage monitor would be a wise investment, Icm makes them they where fairly inexpensive great protection and usually has fault codes and auto reset ,they can be helpful. Have you tried by passing the soft start control ,possibly the issue may be in its electronics or possibly to sensitive for voltage or phase monitoring .if voltage or phase drops out it either the control or the pole this would be after re checking all wiring Peace and good luck clammy

pecmsg

The High leg or Wild leg goes on the center taping!

hot_rod

Time to call in a pro on this one. I'll stick with the mechanical, pump side, of this job
It looks like these soft starts offer a bunch of different protections in one box. I thinke this replaced the basic "heater" type overload a while back.

It looks like it is trying to protect against a phase issue.

One of our members is an elevator service technician, I think he installed this, and would be the one to troubleshoot it. Thanks for the suggestions.

clammy

Yeah some times its better to leave it to those who are the ones responsible for the wiring and or suppling of motor when there’s issue . Possibly the parameters on the control may be to tight for the application . Thanks for the center tap reminders it been a long time .peace and good luck clammy

Solid_Fuel_Man

Yes, you have a high leg or wild leg 480V delta. Most likely only have 2 transformers on the pole and not 3. Called an open delta. 

This is done in rural areas around here as the poco only needs 2 phases instead of all 3. The 3rd phase is "manufactured" by the reactance of the windings in the transformers. It isn't true 3 phase, but it will spin a motor. 

Many 240V open deltas here for rural agricultural refrigeration and irrigation. 

A 480Volt Wye system would be 277V to ground on each leg. 

EBEBRATT-Ed

Sounds like a wild leg system. Are any of the phase wires marked orange??

Jamie Hall

I continue to wonder... I think we are kind of agreed that what you have is a high leg or open or whatever delta. Which will work very well -- normally. But they tend to get a little squirrely when the power factor of the load is not 1 (pure resistive) and if it's well off 1 -- which it will be starting an inductive load like a motor -- the voltage relationships and even phase angles can get cockeyed.

I think a phase and voltage monitor might show some interesting results...

hot_rod

Had the power company out, it is a 3 transformer supply with one "red" or high leg that measures 460 to neutral. The power company tells me they always mark the high leg as red.
Finally got it running today. Seems to be a connection at the pump, as soon as the cover gets put on it trips the soft start. The electrician re did all the connections and it starts and runs fine.

No obvious arc at the motor junction box. The soft start must be sensitive enough to detect a loose or grounded connection? The soft start also errors with the motor leads disconnected from it.

EBEBRATT-Ed

Glad it's fixed

EBEBRATT-Ed

Don't run into the "wild leg" system very often. Usually in older buildings. It was usually used in buildings that needed 3 phase service and only needed a small amount of 120/240 power like a small machine shop with a small office, where the office needed 120-volt power but most of the load was on the 3 phase for motors.

We had an old school where we were changing a 3 phase oil burner one summer. The old burner was down in a pit which had constant ground water so the had a 120 volt sump pump in the pit. Even in the summer there was enough water to make the sump pump run fairly often.


So when we removed the burner and it's wiring the sump pump wiring was in the same conduit that we had to remove.

My boss who was the electrician I learned from got a scrap pc of romex and hooked it up to keep the sump pump running overnight (we were coming back the next day) so the pit wouldn't flood. We tried the pump and it worked.

Wen we got there the next morning the pit was flooded and the sump pump motor was hot enough to fry eggs on and was off on internal overload.

You guessed it. He had temp wired the 120 volt sump pump to the **** leg (he didn't check so we didn't know it was a wild leg system the first day)

He rewired the pump to one of the other legs and when the motor cooled down it was fine. (today's motors wouldn't have stood that.

Strange thing is that old school had two electric service which is unusual and usually not allowed.

Some things you don't forget