3ph Motor

[Echo-Star]

Good evening all

Took a look at the motor today, 3ph 2hp and no sign of the delta wiring symbol.

Removed the wiring cover to see if there was any information below the cover, there was nothing. What I did notice, that there was three wires only, coming out from the motor, I called Fraser & Macdonald, brooks crompton specialist based in Glasgow. Told the guy that I had this 3ph motor that I'd like to have the windings reconfigured to run on 240v delta. Anyway I got asked some questions IE, hp 2, kw 1.5 rpm 2800 and asked how many wires are coming from the motor, I told him three. There must be more than 3 wires he said, well no there is not.

Got talking about the price of a new 3hp brooks motor and quoted £375 +vat so looking at 450ish.

He then told me that this 3ph motor can run off 240v however It does not facilitate for delta wiring ?

Been reading lots of threads regarding this subject on the forum, as well as vid's on utube and just when you think your getting your head round all the wiring VFD's, then find myself with a motor with only 3 wire's

Can anyone help explain this, and best way forward for me.


Any help would be most welcome

Regards Rob

 

[Spectric]

Are you sure there are only three wires? It is possible because I picked up a big motor some years ago for a compressor build, it was 12 Hp and that only had three wires, I needed all six wires so I could use a Star Delta starter. After some digging I found out it was a lift motor, wired Delta only. This meant I had to use a soft start and dump valve.

Look deeper, even remove the terminal plate and somewhere the winding wires must be connected, you have three the others must be all connected together to give a star configuration, unless they are all wired within and just the three lines have been brought out for connection that would suggest a special application motor.

 

[Echo-Star]

Yes Spectric

Now that you mention it, and that would make perfect sense, the wires must be connected within the motor housing, as I did take the terminal plate off, and as stated. Three wires

Regard

 

[Ttrees]

If you wanting to take the motor apart, then it might be a good idea to draw a line down the length of the motor to aid reassembly of end bells later (if there is no distinctive orientation of them)
If you are planning on using a VFD/inverter with this motor...

Myfordman (Bob) has written an extensive article on induction motors and VFD's
which is more than just worth a read.

Induction motor information here https://drive.google.com/file/d/0B_GZrXNsNxTlQzd6aldlQjJtUDQ/view?usp=sharing

Are you planning to get the 'star point' dug out of the windings?

 

[guineafowl21]

It’s pretty common for older motors to be wired in permanent star 400V, and to only have three wires available. If so it won’t run properly with 230V. Your man in Glasgow doesn’t sound too knowledgeable.

The star point is most likely buried in the windings.

 

[EddyCurrent]

This is my "go to " place for motors and drives; Inverter Drive Supermarket: Buy VSDs, Electric Motors for Speed Control
A Brook Crompton motor will not be cheap but there are others that will do the job nicely.

 

[Fitzroy]

As GF21 said. The motor on my Wadkin planer was of this type and I had to find the star point, open it up and solder on three new leads to take outside the motor.

If you are going for a new motor just get a single phase, then no need for a VFD.

Fitz

 

[Echo-Star]

Thanks for all your input guys,

I've been doing research since I put up this post, and apparently this motor cant be run from 240v though an vfd, due to the wiring being wye fixed internally to the winding. The only option would be as Ttrees said and take it apart. Not a job that I'd be confident to take on, not being familiar with this task.

Guineafowl, Your right about this so called expert from Glasgow, as I have discovered this in an hour from Spctric's feed back on the web. whereas a pro could have told me at the drop of a hat.

EddyC, I will check out the web site, and keep options open

Fitz, what you've described, Ttrees also. That would be my only option to get the use of this motor. I'll have to put that to one side for the time being.

I will go for the new 3hp single ph option and go check out Ed's web site. I will also require new switch gear

Thank you lads

Rob

 

[Fergie 307]

If you have a vfd why not buy a second hand 3 phase, much smoother. I picked up a fairly recent 3hp 2800 rpm dual voltage one for my lathe for about £60. Loads of them on e bay.

 

[Spectric]

Rob, you obviously do not have a three phase supply so why not just buy a single phase motor and no problems.