Main Breaker Problems

What is your amperage draw and breaker size?? Is there a time delay on the starter? Does the wire heat up when the compressor is running? What is the full load amperage listed on the motor? What wire size are you using? How's the quality of your power supply? Frequent outages or brown out conditions?

Thanx for replying

Sorry for a typing error it is 160kw motor

Cable size 95mm

There is a time delay between star and delta

Breaker 630a

Full load 280a

The cables are warm but not hot

the running load amps are one thing.....you need to know the draw on start...don't rapid cycle it, keep it to a minimum!

it TRIPS when delta kicks in the motor is at full speed then

As I am sure others here will also say, you do need to know your "instantaneous" current draw in both star and delta when starting. With such a starter, there will be two peaks.....

I suspect that the breaker is being "partially" tripped at each start. Eventually this causes "creep" and the breaker drops off at one of the later starts.

Remember, an induction motor, depending upon some internal design parameters of the motor and the starter, plus mechanical load, can often take between 5 and 8 times the normal full load current at start up.....

In my experience, 6x is quite normal and to be expected/planned for.......which would explain the tripping.....6 x 280 = 1480 amps possibly, in a worse case situation...though I suspect yours will be less than that, or it would trip even more often.

Breakers for such motors are generally designed to handle a certain level of starting current, though you local code will tell you more possibly.....

Can the motor manufacturer shed some light on the question....?

Also, Electrical Code where you are needs to be checked for the cable sizing, even just getting warm is to me a "heads up" to do that.

Especially if within say with a foot (30cm) of a connection!! Now that really gets me "hot under under the collar connection!"

I like all cables and their connections to be "cold" myself.....but that's possibly just me......I always go to the "safest" set up!!

Warm/hot cables, seen over the years, simply hardens the plastic, which at some point will just "flake" off if mechanically moved or even touched!...highly dangerous.....and seen VERY often.....

Some sort of IR scanner can be used to check temperatures of live connections, even a modern laser thermometer for under US$50 nowadays, may shed some "light" on the subject!

I have even used my Sony video camera, in total darkness, using the ultra low light setting, which is very sensitive to IR. Quite useful......costs me nothing to use it!! I am sure that other similar units will do exactly the same.....

Saving a few Dollars on going for the smallest diameter of cable possible is to my mind:-

"saving money no matter what it costs!"

Quoting an old German saying that I am fond of!!

The current at the point of Y∆ transition can be 10xFLC.

There's no fault other than bad design.

Thank you

What do you suggest I do ??

Get it designed correctly. Consult a qualified local Electrical Engineer.

you should at least get a free cup of coffee for that answer, well done

Should you guys be in Cape Town I will take you out for lunch

P.S My boss is an accountant

Than You for the reply

I will try the "Roll Over"trick but the next question from my boss will be but it worked like this from the year dot?? My only explanation is that the circuit breaker was 30 odd years old ? Can this be the problem ? My idea is to go the soft starter way.

Thanking you

Malcolm

"...but it worked like this from the year dot??"

Something has changed in your system. It might not even be to your own facility, i.e. someone moved in down the road and the utility changed a transformer, or added line capacitors to boost the voltage because there is more load now. Could be any number of things out of your control or knowledge. Again, that's a known risk of Star-Delta starting, it cannot adapt to changes in the system. With a solid state soft starter if the system changes, you change the settings.

Remember THIS one you helped me with many moons ago?

The ability to start in the morning but not midday suggests that conditions at the breaker are thermally borderline. Over many years, dust may have accumulated, slowing heat dissipation. Or connections may have vibrated loose, creating hot spots. A thermal scan might tell more.

GA on the IR camera. That is becoming a very efficient tool to track down problems in the plants. What used to take hours to troubleshoot often times can be found in less than 5 minutes now. Especially when you are dealing with higher voltages.

I hear flir is partnering with smart phone providers to have ir viewing capability built in to the phones....that will be something handy to have at the ready...

yes here it is...

http://investors.flir.com/releasedetail.cfm?releaseid=955547

they've been around a while, heres a pretty good idea of its capabilities

looks like my link didn't make it

https://www.youtube.com/watch?v=WPtizsZ7nis

Being that it only trips on transition, I'd say that it's not likely a thermal trip, it's an instantaneous trip.

Yes, but then why does it happen after noon but not in the morning? Any reason those two factors couldn't combine?

I suspect a voltage drop in the system caused by many other loads being present at certain times. Morning starts don't cause a trip because these loads are not present. E

If you are so sure, why not post using your own avatar?

As you don't, you are not sure about the validity of your comment either!

I agree with that, an invalid answer!!!

People post anonymously to annoy TROLLS like you!

How misguided and ignorant can you get??? See all my "LOLS"

But at least you gave me a great laugh!!! Many thanks for that, we all need a good belly laugh from time to time.

Many others too I would guess!!!

OH!, by the way, let me educate you a little better, a Troll is someone who posts anonymously!!!!

.....and you didn't know!!! Hilarious!!!

See this website, where the only difference is I do not let childish people like you upset me as I find them rather pathetic and eminently laughable:-

anonymous-trolls-and-posters

Where you can read this:-

Usually I'm pretty easy going and let most things roll off my back. One thing that has bothered me for some time and continues to do so are those who post anonymously and then attack people when they don't agree with what the other says or just to be down right nasty and attack someone.

There is no place for that kind of cowardice in this field or any other. Why is it that someone can insult someone else because they disagree with what the first person said and think they can hide behind an anonymous post? Instead of being man or woman enough to use their real name, they feel like they can hide behind the safety of the internet under anonymous moniker to attack and belittle the person they disagree with.

So it quite obvious WHO made the mistake here, YOU!!!

By the way, you MUST now remain anonymous, as you would not live it down if you outed yourself after such a childish stupid mistake......

So now we all know that you are Troll in this case, also you should read this, its VERY informative:-

internet-trolls-are-narcissists-psychopaths-and-sadists

But I seriously doubt that you will read it, FAR to close to home for comfort!!!

But thanks for the great laugh, got anything better to say?????

Also, I am pretty sure that I know who you are as well!!!!! No surprise there....

That was not funny, except in the farm sense.

The responses all have merit and are logical deductions to the problem posed.

Though the electrical characteristics have been considered it infers then, that the mechanical driven component i.e. the compressor is completely fault free.

If the circuit breaker is thirty odd years old then the motor and compressor I assume are of similar vintage.

I have seen on similar plant long acceleration times and if the auto unload/load control has a Gremlin then the compressor starts to load prior to the transition at normally 80% of full load speed.

The now loaded compressor exacerbating the required current drawn in the first couple of cycles of transition.

Gut feel as a shift electrician ambient related problem with circuit breaker characteristics requiring testing after mechanical issues if any eliminated.

Lookup the definition of troll on Wiki.

白目

dear malcolms, is this tripping occour in front of you any time. what is behaviour of motor this time, any sound or abnormalty is there.If not than check operational mistake. Is any other compressor is running in parellel of this. If yes than check ,that air delivery line is common . Many time when we changeover of compressor than if operator is not expert of system than this tripping is occour. Air presser of other compressor force another compressor if valve are not close or line is not seperate. If system is single than check your breaker o/c and time delay setting, also check breaker internal contact. Check the time delay between star to delta if tripping comes on delta time.