Hooking up a bandsaw from single phase

Aegir01 · Nov 10, 2023

Hello all,
I signed up here for a little help. I bought a 3 phase bandsaw and went down the rabbit hole of VFD’s etc.
‘The motor is 3 phase 400v and I have 1 phase 240v (Australia) .
So I bought a VFD that has an input of 240v single and an output 400v three. It’s currently in the post.

I opened up the box on the bandsaw to see where I need to wire in the section between machine and VFD. Not what I was expecting to find And now a little confused. I have every intention of getting a local electrician to come and do it for me, as this is beyond me, but my question is what am I looking at, because I did not expect to find the transformer, and the markings on it say 240/400 .
So does it mean I only needed single to 3 phase and not the volt converter?

westward10 · Nov 10, 2023

I suspect the transformer is possibly for a control circuit. It is rated at 30va which gives a secondary output of 0.13A so it is in no way rated to provide power for the motor.

Aegir01 · Nov 10, 2023

westward10 said:
I suspect the transformer is possibly for a control circuit. It is rated at 30va which gives a secondary output of 0.13A so it is in no way rated to provide power for the motor.

Ok, so not part of the volts in or out.

westward10 · Nov 10, 2023

Aegir01 said:
Ok, so not part of the volts in or out.

I would not have thought so.

timhoward · Nov 15, 2023

A further complexity is that a star/delta motor starter will probably be required if there isn't one integral to the bandsaw.
My thinking is that the plate shows wiring for star and delta configurations which is a pretty strong clue that it is an induction motor designed to start up in star configuration and then change to delta once running.
I'm not an expert industrial sparks but my hunch is at over 3kw it's beyond the power that a simple DOL starter should be used?

Marvo · Nov 15, 2023

I think the motor star and delta options are just two permanent wiring schemes and it would be wired direct on line. According to the IEC symbol on it, the transformer is a safety isolating transformer with no built-in short circuit protection. As Westward said, it will be to supply a control circuit.

westward10 · Nov 15, 2023

3kw 3 phase 400v motor not likely to need star delta starting.

brianmoooore · Nov 15, 2023

westward10 said:
3kw 3 phase 400v motor not likely to need star delta starting.

My knowledge of VFD's is limited, but I'd expect soft starting to be programmable into it.

TerryB NZ · Nov 20, 2023

The motor is a 3kW 400v Delta motor. As you can see you would need 690 Volts to run it at full power in star. This is common for a larger motor and allows for the option of putting your 400v into the star configuration as a soft start to get the motor moving with low current draw and then switch after a few seconds in to delta, lessening the inrush current. This can be done manually with a switch
IE: OFF-START-RUN.
Buts said the transformer will be for control circuit, it is wired 400v in and 230v out, so I would be guessing there is at least two (probably three) contactors and a timer in there to switch from star to delta on start.
As long as your VFD can do 3kW and your 240volt supply can handle the inrush currant you should be good.
Hope this makes sense.

James · Nov 20, 2023

Am I missing something here?
motor is 690/400v
you have a single phase 230v supply.

every single phase vfd I have Come across has no way of increasing the voltage.
so 230v 1ph becomes 230v 3 phase.
this is fine if the motor is 230/400v as you can change from 400v star configuration to 230v delta configuration to suit the 230v 3 phase from the inverter.

or is there someone out there making vfd drives that step up the voltage now?
if so, can you give an example?