Please can you help - Motor and control panel problem

[mark270981]

Hi all (I am hoping our resident expert can help me out here)

I am hoping you can offer me some advice please, as you may have seen I have purchased a new filter and fan unit. The fan itself is 15kw, the company who supplied the fan (used) had a new control panel made up and sent out to me.

Once the electrician had wired this control panel up and pressed go, it kept cutting out when switching to delta. The trip was occurring at the thermo overload. we turned the dial up to 18amp and tried it then the TO went pop (we've ordered a new one)

The rating on the control board is 18amp

The rating on the motor is 27.1amp

The control board people say this is correct, as the rating is calculated as 0.58 x amp required.

The electrician checked the windings on the motor which were fine.
He also checked the voltage in to control board and voltage out which all read fine upto the Thermo Overload (tested after it went pop)

He thinks the wiring diagram from the control panel people is wrong

I wouldn't normally ask but I have a workshop which is down and cannot function

Is the control panel under rated?
Is the wiring diagram incorrect?
Both?

Or perhaps something completely different?

Many thanks in advance.

Regards

Mark

[tusses]

wow ! that's a lot of watts for a fan !

Have you PM'd Bob ? might be quicker than waiting for him to see this

[mark270981]

I have sent a PM to Bob, cheekily directing him this way, I thought whatever answer he provides would be great for everyone to see should he wish us to do so.

Yeah it's a lot of wattage, so imagine my disappointed to not feel its full force on Friday!!!

[tusses]

I wouldn't get anywhere near that wattage in my workshop if I switched everything on at once ! lol

[9fingers]

1)First thing to check is that the U and V 1,2 &3 are correctly connected. This is critical for star delta switching

2)The diagrams don't show how the star delta switching is being controlled. There should be a timer and interlock switches somewhere.
If there is a fault in that section then it could be that C2 and C3 are being engaged at the same time which puts a dead short across all three phases.

3)Also you don't say if the option to bypass the overload when in delta (normal running config) has been selected - this is the dash-dotted wiring option.

I would assume that is has because the overload should otherwise be rated upto at least 27 amps.

Personally I think it is dodgy practice to bypass an overload rather than fit two, one each or the correct rating for star and delta modes - This means the installation is not protected in the run (delta) mode which the mode it will spend nearly all its life in. Only saves a few quid.

So check 1) above first
(corrected version now )
4) Disconnect two of the three links between C1 and C2 at one end of each. Insulate the bare ends. This disables the delta running mode. Now start the motor. C1 and C3 should engage to start the motor in star. When the controller decides to switch to delta (20-40 seconds later maybe), C1 stays engaged, C3 drops out and C2 should engage. because the links are removed, the motor should stop. If it continues to run, then it means C3 is still engaged and the controller is in an illegal state and needs investigating. This method should at least let you investigate without the "bang"

If you can check 1) and answer 2) and 3) and tell me what happens when you try 4)
we can try and work out what is happening.

A decent spark up to speed with motors ought to be familiar with star delta switching and able to work this out.
If he is a young chap, it is possible he has been brought up on soft starters - the more modern way to start up big motors.

hth

Bob

[mark270981]

That's a wonderful response Bob, I appreciate your time on a Saturday to reply.

There is only 1 overload I believe - i will post a picture for yours and everyone elses reference of the control panel.

Its always nice to be educated in something totally different.

I will direct my sparky to this to have a look at this weekend, and hopefully we will get up and running by Monday lunch time.

I may have to come back to you if not, - I hope this is ok?

[mark270981]

I wouldn't get anywhere near that wattage in my workshop if I switched everything on at once ! lol

Lol - when I had the drum sander it had 2 no 15kw motors plus a 7kw for the bed.

[9fingers]

Note that my first reply had an error in it and I have now revised it.

No worries about a saturday - when you are retired all the days are the same!!

Bob

[tusses]

for me, when you are self employed .. all the days are the same too ! lol

[9fingers]

A further thought!

I was called to look at a star-delta starter system a few months back all the contactors seemed to sequence properly and a quick measure of winding resistance seemed OK. It had me going for a bit until we got the motor terminal box open and found two windings with burned wires. They each measured ok but were connected together by the shorted wires and so ran perfectly in star but blew the main fuseboard when in delta.

Could be something daft like that?

I've got a dead CNC spindle to fix tomorrow but let me know how you get on and I'll try and advise further tomorrow evening/Tuesday if needed.

Bob

[mark270981]

Hi Bob

It seems that that 2 wires were terminated incorrectly into the motor itself - There were set of wires already terminated into the box on the motor with a tail of about 4 metres, so rather than buy 4 more metres the sparky added an extension and junction box........He reckons whoever wired the motor up originally had wired it wrong, but rather than correct his mistake at source he switched the wires in the control box..........Suffice to say following your instructions you kindly wrote out for me the machine now runs like a dream!!!!!!

Many thanks

Mark

[9fingers]

Excellent news Mark. Glad to have been able to help in some small way.

Cheers

Bob

[mark270981]

You were a huge help thank you.