What's new
What's new

Idler motor requirements - Australia 240VAC single phase to 415VAC three phase RPC

callielli

Plastic
Joined
Mar 9, 2020
Location
Melbourne, Australia
Hi guys,

I am in Australia, recently I have purchased my first machine, it's a S1 Bridgeport Vari-speed.

Much like most people who decide to build the RPC, I am tossing up between idler motors.

I'm a robotics engineer so understand electronics however 415VAC is not an area I have spent much time working and this voltage is less-friendly to trial and error for obvious reasons :nono:

To help clarify my decision, I was hoping someone with more knowledge could assist.

1. 3 Phase motor selection.
- Does the idler motor have to be 240/415V wound ie: can I use a 415VAC induction motor like TECO 3 PHASE ELECTRIC MOTOR 5.5 kW 1440RPM - 380/415AC 12.4/11amps 38mm shaft | eBay

I note there is only a delta rating at 380-415VAC.

2. Is there any advantage or disadvantage to running a certain pole count/RPM?

3. What practical numbers to guys look to build to ie: 5.5kW idler will happily power ##kW of downstream power?

:scratchchin:
Thanks for any help!
Callum
 
Well I dont know metric electric motor specs but I can give you American... 7.5 hp, best if it is 2 pole (3600) 480 volt star (Y)winding to run a 480 rpc, every motor will be a little different as far as the kvar that is need to start and run the rpc...Phil
 
Hi Callum,
I think $250 for a used 5.5kW 3phase motor is too much. But maybe you live in a remote area and free delivery.If your plan is to build a 415v 3 phase RPC all you need to focus on is 415v input and that at 5.5kW will require connection in Delta.
I think 4 pole 1420 RPM or even a 6 pole would be best. Now, as for what power you can get from a 5.5kW idler well you have not mentioned what transformer arrangement you will be using. Is this for home/hobby use or you may be putting it to work. A lot of people want a RPC to run a lathe, say the lathe is 5HP, if it was for leaning/hobby they would be lucky to use 2HP.
What method of starting this idler are you thinking of using?

Jim
 
Hi Callum,
I think $250 for a used 5.5kW 3phase motor is too much. But maybe you live in a remote area and free delivery.If your plan is to build a 415v 3 phase RPC all you need to focus on is 415v input and that at 5.5kW will require connection in Delta.
I think 4 pole 1420 RPM or even a 6 pole would be best. Now, as for what power you can get from a 5.5kW idler well you have not mentioned what transformer arrangement you will be using. Is this for home/hobby use or you may be putting it to work. A lot of people want a RPC to run a lathe, say the lathe is 5HP, if it was for leaning/hobby they would be lucky to use 2HP.
What method of starting this idler are you thinking of using?

Jim

Hi Jim,

Thanks for taking the time.

I am in the Metro area so could easily enough find other options, I guess I just posted that one as it was on my shortlist - what budget would you allocate for a 415V 3 Phase 5.5kw idler?

1. Is the main reason for 4,6 or 8 pole the lower RPM? I imagine this would be helpful to keep acoustics down?

2. As it stands, I am looking to run relatively low-power three phase machines.
- Drill press (3/4HP)
- Power Hack Saw (1HP)
- Bridgeport S1 (2HP)

+ plans to add a lathe in there at some point in the future. I can’t imagine it is going to be anything heavier than 5HP.


The machines get a workout as far as hobbyist level goes but there is no requirement to ever run more than one at a time, would be nice to have some power in the system, should it be required.

I am a little confused around what is and isn‘t suitable as an idler.

As I understand the motor needs to be 240 Delta/415 Star, however I see many builds with older 415V 3 Phase motors which I assume are wired in a single voltage arrangement?

I also have access to a 415V Delta 620V Star motor however my assumption was this would be too higher voltage and hard to start given the delta is 415V.

I will start with capacitors at this stage.

Thanks again for your help.
Callum
 
Hi Callum,
To build a RPC is an easy project. If your plan is to have a RPC that outputs 415v 3 phase. With your anticipated loads a welding transformer would make a suitable transformer so 240v in 415v out. Now any 3 phase Induction type motor that it's rating plate says 415v, ( in the HP you are requiring it )will state Delta or a Delta symbol, now if it was a lower HP it might state Star or a Star symbol. So a 5.5kW motor will be 415v Delta in Australia 99.999% of the time and this motor has to be connected in the terminal box of the motor in Delta.

When you say the Metro, are you meaning Sydney?
If you look on Gumtree, I thought I saw someone with several 3 phase motors, one 5.5kW at $50 or $60 each.

2 pole motors very noisy fans and harder to start, 4 pole good but if a 6 pole came up would be good.
I hope you understand you can just about use any induction motor that operates from 415v as an idler motor, (in this case). So are you going to use a welder as the transformer.

Jim
 








 
Back
Top