Changing from star to delta ?

[Pete.]

If you're fitting a single phase VFD, you need it in Delta - simple as that. There are some that output 415V, they need star, but 99% will be delta.

 

[Luke]

there's 3 windings, in star one end of each winding goes to a live phase, the other ends are connected together, that center point is essentially neutral

each live is 240v, voltage between live connection and center (neutral) point is 240v

in delta one end of a winding goes to a live phase, the other end goes to a different phase

voltage phase to phase is 415v (ish)


....isn't it?


EDIT: googled a picture

Yes you're right, if you're supplying the windings with 415 3 phase, which we're not in this case, as we're discussing a 240 V input single phase inverter which will output 240 V across the phases, not 415 V, hence needing to change the windings. The inverter and motor don't need a star point/neutral but the motor does need the correct v/f ratio.

As has been described above, star vs delta doesn't really matter. Big motors are 415 V delta 690 V so no use with 240 V inverters if you want to go to 50 Hz. What's important is that the motor is supplied with a voltage at the correct frequency ratio. With a smaller motor, wound 230 D, 400 Y, on a single phase inverter, the optimal solution is going to be to wire it Delta.

 

[ronan]

I do know that with any of the smaller, mill, lathe, grinder motors i have worked on, connecting vfds to, the motors have to be in delta. Which is why i asked was it ok to change this motor from star to delta.

You can buy vfds to run star only motors off single phase, but they are very expensive.

Oddly this motor, and the hydraulic pump motor, do not have any markings that i can see.

 

[knighty]

my mistake, I see where I'm confused now, I thought the inverters were 240v on the phases, but couldn't cope with phase to phase power

240v phase to phase explains it all now


I have a machine with a few inverters in it, they're all 240v phase to neutral (haven't checked phase to phase), I assumed the were the cheaper ones, guess they're not :-)