# Electric motor question



## DTR (4 Dec 2015)

Afternoon all,

I've found recently that the motor on my (new to me) BCA is making a bit of a racket. It doesn't matter if the motor is on load or off, but the funny thing is it only makes a racket when its powered. Off load, with the power cut the noise stops and it runs down smoothly. That rules out the bearings. As it winds down, at some point it makes a clicking sound which I assume is the centrifugal switch closing. The motor is 230V, single phase (photo of the data plate to follow).

Any suggestions as to what it might be? I'm not afraid to open it up if need be, although getting it off the back of the BCA will be a bit of a *******.

Now, here's the other thing.... If I need to replace the motor, I'm led to believe that the best option is to go 3 phase with a VFD inverter? The speed control would certainly be useful, in fact I'm leaning towards a 3ph for that reason alone. Also, would I see any advantage from the reduced torque ripple?

Thanks


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## DTR (4 Dec 2015)




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## NazNomad (4 Dec 2015)

Initial thoughts were...

1. Brushes

2. Has something got into the motor and it rattling about?


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## mind_the_goat (4 Dec 2015)

No expert but why rule out bearings? The forces are different when it's powered to when it's not so the bearings will be loaded differently.


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## Inspector (4 Dec 2015)

Fan?

Pete


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## Myfordman (4 Dec 2015)

There could be a winding problem causing the noise only when powered. 
The magnetics of motor could be causing axial thrust on one bearing causing it to be noisy.

To be honest, a mill with continuously variable speed is so much more of a pleasure to use I'd replace the motor with an inverter rated dual voltage 3 phase 4 pole motor and drive it from an inverter.


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## DTR (5 Dec 2015)

Myfordman":1m1jn9wi said:


> To be honest, a mill with continuously variable speed is so much more of a pleasure to use I'd replace the motor with an inverter rated dual voltage 3 phase 4 pole motor and drive it from an inverter.



I'm not usually one to throw money at a problem, but I think that's the best option. Any suggestions on brands, dealers etc?


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## Myfordman (5 Dec 2015)

Motors: I normally specify Marelli or TEC as good balance on price and quality. Myself, I use what ever I can get my hands on.

I do a lot of work with inverters and tend to stick to brands with good documentation so I can programme them readily without learning new stuff. My preference is for Siemens for the above reason but there are plenty of other makes out there.

I tend to supply inverter solutions for "difficult" jobs eg star wound 415v motors when there is only a single phase supply available or multi motor machines needing logical interlocks between motors where I can use my skill to dig people out of difficult motor holes.
Yours would be a simple 240 in, 240 out inverter straight off a shelf programmed according to the book.

In your case I would say get ones that come with a manual or you can get download online. Buy used inverters on fleabay.
For best performance at low speeds, look for inverters that offer "Vector mode" or "Sensorless flux control" EG Siemens Micromaster Vector or Micromaster 440. Other brands will work just as well.

Have a read of my paper on the subject which has been kicking around on this forum for years under my pre ban username. I think there is a link to it in the stick at the head of the metalwork section by CHJ.


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## graduate_owner (5 Dec 2015)

Hi DTR,
I bought a 3 phase inverter earlier on this year, from Willpowerelectrical in eBay. Their feedback was 100% positive and they answered an few concerns I had so I was happy to buy from them. When I had occasion to ask more questions they responded promptly and knowledgeably. The product is an Invertek and is British made, 2.2kW for £160 which I thought was very reasonable. They are currently £210 plus carriage.
Just a few points though. My previous inverter stopped working and I suspect it may have done so because of a dusty and damp environment. The Invertek instructions say to enclose in an IP 65 enclosure, or you could buy a IP65 model invertek but they are considerably dearer. I chose to build an enclosure with thermal cutout switch and vents with filters over them.
Also if you run your motor slowly then bear in mind the cooling fan will also run slowly and not cool the motor efficiently. You can get new motors now that are designed to work with inverters but I have no experience of them.

Finally, variable speed on a mill is just brilliant. I tend to have the belts arranged so as to give slow speed, then the motor runs fairly quickly (fan speed again).

Hope this may be of some help.

K


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## graduate_owner (5 Dec 2015)

Hi again DTR, I forgot to mention, you usually can't connect your inverter via the existing switchgear as the inverter needs to be connected directly to the motor, also the motor needs to be dual voltage and connected in delta mode ( lots of info on star delta on the web).

K


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