Excessive Arcing of Controller Magnetic Contacts

Call an electrician. He can help you out.

Thank you for your reply but he told me you might google it...;;

There is no point in asking lyn to do it; it is better to do these things oneself so as to save time.

#2 reply: I don't want there to be any misunderstanding.

I contacted my technician and asked for helping me in this issue but he told me it was because of power supply issue and you might google it because it was common issue. I just wanted to hear other advice in this forum. Thank you for sharing your opinions.

Are you in North America and you have 480V available, or are you in some other part of the world where you use some other voltage, such as 415V? Because that would explain why you are reading 412V right there.

If you have 415V available and the motor is rated for 460V, it can posdibly still work, but not if the machine needs the full kW of the motor, because the difference in frequency will lower the kW capacity of the motor, even though torque will posdibly remain the same. Most machines work on torque, not power, but we have no idea what your machine is.

The arcing you show in that picture does not appear on the outset to be excessive. All contacts arc when they open (and a little when they close). But are these welding shut? That would be a problem.

If you want real help, you will have to do a more thorough job of describing everything about your system and issues. Otherwise you can expect further abuse.

Thank you for your reply.Our normal specific voltage rating is 460 V, 3 phases, 60 Hz.When we do not run our electric driven fire pump, it has 440V but after running it with load, the voltage dropped to 402 or 412V.The controller provides 400A magnetic so we consider that the capacity of current is not sufficient. We use wye-delta controllers at site. we installed motor connections as I attached(According to guidelines). Can this connection be an issue of arching matter?

You need to get an Electrician involved. Someone who can look at it and find out what's wrong.

Is this a new problem, or has it occurred for an extended time? Is there a mechanical interlock between your wye and delta starters? What is this motor driving? Is it starting unloaded? Which starter is arcing - wye, delta, both? (This is really not my area of expertise.)

Fire pumps, depending on the design, are often running 24/7, simply to maintain water pressure on a fire main piping in say a building, or even onboard a ship or possibly on a large area for a factory.

It is possibly not just simply switched on an off when needed.....in my experience......

I am not saying your comment is in error, but, in my 39 years of experience, I have never seen a fire pump ran 24/7 to keep pressure on a sprinkler system. I have seen lots of "jockey pumps" (small 1-2 HP motors) used to maintain pressure levels but never have I seen a main fire pump ran that way, sure would be expensive on the power bill.

On ships, there would be at least one full sized pump running 24/7 to keep the fire main ready for instant usage...

Alarms would alert the engineers to any pressure loss immediately.....

The OP has not told us if its a 24/7 or not or whether its on land, sea or even air!!

We are just left guessing....and covering all bases!

Never looked at fire fighting systems on ships so I will defer to your knowledge. Seems like a waste of energy to me though.

Must have been a military vessel, because we all know, energy is free on a military vessel...

All kidding aside I agree with you on the Jockey Pump issue, but this might also be a semantics issue as well. On a ship, the fire pump may have been one of many smaller pumps, cordoned off into sections of the ship separated by bulkheads in case they were sealed off, as opposed to a land building fire pump system where you have one large 200HP fire pump for the entire building and a small jockey pump to maintain pressure. So if instead the ship has 20 x 10HP zone fire pumps all tied into a common header, it doesn't make sense to add a 21st pump as a jockey pump, you just use the fire pumps themselves as jockey pumps and alternate them.

I can understand that, it was a good explanation, thanks.

On ships the firemain pumps that are run (in my day) are the "Big Boys".......maybe nowadays there have been redesigns.

My next question to the OP is does this contactor supply the Jockey or the main pump? If its the main pump, surely it is hardly ever in use? Fires every day? I think not!!

We need more info....

JRaef,

I apologize for more or less repeating what you stated in your post. By the time I had composed mine, you had already posted, with much more detail.

One detail not mentioned so far, is the ability of a contactor to maintain hold under voltage drop. There are contactors that can do this.

If time based, the transition from star to delta could be miss-timed.

What I would do:-

The contacts are definitely over heating badly....maybe not just in "starting", but also in "running" mode.....I assume that the motor has been checked out carefully for shorts and unbalanced fields?

Assuming that the motor is OK, this post suggests to me that there is too much resistance in possibly the cabling and definitely the contactor contacts.

Voltage is dropping and the motor is therefore taking more current....

With your present set up, even the motor is possibly in the danger zone of over heating as well.....have you checked that out?

Do not take this problem lightly.....it could become very costly and a fire that destroys everything is a distinct possibility....as I believe someone has already mentioned, Lyn maybe?

May I suggest that the cabling size be doubled (you neglected to mention what you have at this time) and the contactor contact current ratings should also be doubled to say an 800 amp. version.

Fusing/circuit breakers to be correct for the motor and load in use.....not increased.

Check the motor starting current through the contactor, you may find it exceeds the contactor rating in which case you may need to upgrade the contactor and/or add a soft starter to the motor to limit the starting current.

Also, your supply voltage under load appears a little too low (check your local standards for the actual allowed voltage drop) so you may possibly need to talk with your power board (or whoever is responsible in what ever part of the world you are in) and get a transformer upgrade (excessive voltage sag is not good for motors or switchgear). If this excessive voltage drop is only during starting then a soft starter should fix the problem.

Let us know what you find.

nice heaters though

Is your powersupply(KVA) capacity enough,did you check for loose connections,is the cable size enough?. For fire fighting starter should not be star-delta(delay) but DOL.

The load current is higher than the contactor is designed to interrupt.

Either the contactor is undersized or there is a downstream fault that is causing the current to exceed the contactor rating.

If this contactor is servicing the fire pump; Keep in mind that the interruption rating of the contactor is the most important factor and contactor selection should not be based on motor full load amperage alone.

Worst case conditions during interruption events need to be considered such as motor locked rotor amperage and the maximum current that can be developed in the circuit during a bolted-fault condition.

I agree with JREF in that if the system voltage is low the motor will pull excessive amperage during starting as well as when running.

If the contactor services more than just the fire pump; It is required that you determine the total load on the contactor and factor the interruption capacity accordingly.

If you have R-C network snubbers make sure they are ok. If you don't have any, get an industrial version. Also add Mov's . All of them need to be across the motor windings because the collapsing magnetic fields are what generates the excess voltages.

Just from the pictures, I'd say the contactors are undersized. Some I have seen are okay in light duty, but in your case I think you need a larger margin.

You may need to parallel multiple Mov's to adsorb all the excess energy released, but you will know this if they cook or explode!

http://en.wikipedia.org/wiki/Varistor

http://www.taitroncomponents.com/catalog/PDF/Passive/MOV%20Selection%20Guide%20&%20How%20to%20Order.pdf

Good luck!

Is this contactor in a factory built and certified Fire Pump Controller? If so... While there may or may not be a problem in this system that needs to be fixed, please, do not modify this fire pump controller in any way.

Doing so will void its certification and have a negative impact on your insurance situation should something happen.

Call Someone More Qualified To Troubleshoot The Problem. PERIOD!!!!!!!