15 hp dust collector 480v problem

[larryc4]

I have a 15hp 480v dust collector that I bought used. When I applied 480v power and turn on the power to the motor control cabinet and pushing the start button the motor tried to start.
When I push the start button and hold it in the motor runs fine, but if I release the button the motor will stop.
Can you try to give me some possible things to look for. All fuses at good.

 

[ScottyUK]

When the main contactor closes there should be an auxiliary switch on this contactor which closes in parallel with the start button and maintains coil current to the contactor when the start button is released. It sounds like the auxiliary switch is not making correctly, allowing the contactor to drop out when the button is released.

The following link shows the general idea:

http://www.seamanship.co.uk/products_/engineering/eng_know-samples/motor_starters.htm

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Start each day with a smile. Get it over with.

 

[Skogsgurra]

I think that there are better and less ambiguous diagrams available. This one - showing a "contractor" coil, open overcurrent trip contact (should have been an NC contact) and main contacts being too short to do their job - is more confusing than instructive.

Searching the web didn't bring much. Are there no good diagrams available?



Gunnar Englund

http://www.gke.org

 

[machmech]

Hi skogsgurra

This link may help but I would prefer you or ScottyUK did the explanation. Im here to learn and for sure not advise.
Still wet behind the ears!

Chuck

http://www.elec-toolbox.com/usefulinfo/jogrelay.htm

 

[ScottyUK]

I found the same problem - no decent diagrams! I spotted the 'contractor' typo, but missed the other mistakes.

I wasn't going to post this because it links to a big file, but the 26th and 27th pages of the PDF - marked as pages 72 and 73 in the document - show things properly. And Siemens used proper symbols instead of the horrible ones in Chuck's link!

http://www.sea.siemens.com/step/pdfs/cc_3.pdf

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Start each day with a smile. Get it over with.

 

[machmech]

Wow ScottyUK

A diagram and education all in one! nice link.

Chuck

 

[Skogsgurra]

That's a lot more like it Scotty. Took you some time, heh?

Gunnar Englund

http://www.gke.org

 

[fsmyth]

Good link, Scotty. Gonna save some time in my next class
prep. Is the Siemens reference still active?
Any restrictions on using the doc?
Thanks.
<als>

 

[ScottyUK]

Hi fsmyth, skogs:

Yes, took it ages to find: I wasn't happy with the errors in the reference from my first post, so it had to be improved upon!

Do you mean 'Are the Siemens part numbers being still active?' I think the IEC ones are, certainly the Sirius range is fairly new. Not sure about the NEMA ones.

I'm not clear about restrictions on using the document - it is in the public domain and presumably put there as an educational resource, so I guess as long as you credit the origin of the document, don't alter it and acknowledge their copyright...


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Experience is what allows us make a completely new mistake every day!

 

[ozmosis]

Scotty
You are correct, there are no restrictions on the use of these documents. They are part of a series of educational booklets (called STEP 2000) and include all sorts of useful info from switches to PLC's and drives. I know the chap who wrote the drives booklet and he is more than happy for people to download and read them. They are part of an online training program available via Siemens Energy & Automation in the USA (pity my German colleagues never seem to do such a useful thing...)

 

[ScottyUK]

Thanks for the confirmation. Pass on my thanks to your colleague too - so much of what is published on the 'net is be appreciated by the readers yet we rarely get a chance to thank the authors.


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Experience is what allows us make a completely new mistake every day!

 

[pennpoint]

ScottyUK
Your link indicaating pages 72 and 73! Are good.
But can you tell me why the OL (overload contacts) are positioned on the neutral side of the coil? I have never fully understood this method.

Thank You
pennpoint

 

[dpc]

pennpoint,

This is a long-standing controversy. In general switching of the neutral side of anything is not allowed, but NEMA ICS 2 recommends this location for OL contacts due to the risk of welding of the overload contacts if exposed to short circuits (if control circuit is grounded at some point.)

Since the contacts are normally closed, this problem would not be detected during normal operation.

The NEC would not allow this for REMOTE devices, but it is allowed for an overload relay that is integral to the starter.

But some engineering firms do routinely specify the OL contacts to be on the other side of the coil.

 

[fsmyth]

Thanks, Scotty. I always try to attribute the source, if
possible, even if I only use excerpts. Just seems like the
right thing to do.
<als>

 

[pennpoint]

dpc
I now see the logic.
But you confirmed our procedure, we place it on the hot side of the coil.

Thanks

pennpoint

 

[skiier]

Why are you letting of the button?
You want the motor to run or not?

 

[ScottyUK]

Is that a serious question?


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I don't suffer from insanity. I enjoy it...

 

[waross]

There may also have been some remote device in the control circuit that is no longer present. Look for extra holes in the contactor and any sign of wires cut short.

If the starter is in good shape with no unused holes then locate the auxilliary contacts. Locate the coil, one wire from the coil usually connects to the overload relay which is usually below the main contactor. You want the other wire from the coil. Typically this side of the coil will have one wire to the Start Button that you have been pushing and another wire will go to the auilliary contacts. If there are any numbers on the auxilliary contact they will typically be 2 and 3 not L2, not T2,just 2 and 3. If you find the numbers great, if not just follow the wires.
I'm sure someone will jump in and give you the European numbering in case you have a European starter. Find the wire from the coil to the Start Button and look for another wire from the same terminal to another device on the main contactor. This is the device that you want to check. The wire from the other terminal on this device will usually connect to the other side of the Start Push Button.

 

[itsmoked]

waross; has a very good point.

Dust collectors are notorious for exploding into flames. They are perfectly designed for mixing air with combustionable dust. They normally have lots of fire systems incorporated with them.

There could be some keep alive signal missing now.

 

[jraef]

Depends on the dust being collected. Sawdust, possibly. Rock dust, no.

Methinks the OP was a one-shot wonder who really had no business wiring up a motor starter to begin with because he had no clue about 3 wire control. He probably replaced the start button with a light switch. Then he'll be upset that the motor comes on all by itself after a power failure! Don't laugh, I have seen it a lot.

Eng-Tips: Help for your job, not for your homework Read faq731-376