Misleading motor nameplate

[sysrq]

I have a motor with misleading name plate.

230/400V, 0.18kW, 50Hz, delta/star

There are six screws in the terminal box and only three wires are connected to three of them. It's connected in star configuration, only thing is I can't see any wires coming from the windings to U2, V2, W2 .
Can't get any readings with ohmmeter between the centre point (U2, V2, W2) and U1, V1, W1 , I'm only getting equal resistance between the U1, V1, W1. Can't remember the value now but it appears to be good, I think around 50 ohms, will have to check again tomorrow.

I think it might be connected in star configuration internally. I need delta configuration as it will be running on single phase VFD. Another option is to use VFD with three phase power input to get 400V, 415V on the VFD motor outputs.

 

[Darkwood]

Its internally connected so you don't have the option to change the configuration, I would use a 3ph input vfd, as this will both make use of the existing wiring and not load up 1 ph to approx 3x the motor rating, its possible its been rewound or repaired but I have come across a few myself with contradicting plates, is this the same vfd from your previous thread that you already have.. if this is the case and you want to keep the vfd you could take the motor to a motor engineer to see if its an option to bring the wires out or buy a new dual voltage motor.

 

[Marvo]

Can you take a photo of the terminal block and attach it so we can see? Are you sure it's in star? It's more common to delta connect because you get maximum torque that way. Are there any brass links on the connection block? It's possible the U2, V2 and W2 are connected to the underside of the block and you can't see them so maybe take the screws out of the block and lift it clear to see underneath. I doubt it's internally starred especially if it gives you the 230/400v star/delta option on the info plate which strongly suggests it's designed to be connected either configuration.

*edit* Geez, I type slow, DW managed to reply twice before I managed even one

 

[Darkwood]

Can you take a photo of the terminal block and attach it so we can see? Are you sure it's in star? It's more common to delta connect because you get maximum torque that way. Are there any brass links on the connection block? It's possible the U2, V2 and W2 are connected to the underside of the block and you can't see them so maybe take the screws out of the block and lift it clear to see underneath. I doubt it's internally starred especially if it gives you the 230/400v star/delta option on the info plate which strongly suggests it's designed to be connected either configuration.

*edit* Geez, I type slow, DW managed to reply twice before I managed even one

Not in the OP's case he has it configured in star for 400v 3ph at present and want to connect at the reduced voltage 230v 3ph (1ph to 3ph VFD) so needs to change to delta but because he's reducing the voltage too he will have the same torque in both set ups. You have a point of the star maybe on the --- side of the connection block though

 

[sysrq]

Well theoretically if I set VFD Base Frequency (output frequency at which maximum voltage is
reached) at 25Hz and the max voltage is 200V, then 400V motor should maintain some torque at 200V (voltage/frequency ratio).
Torque demand might be low anyway cause it's a short helical feeder with gearbox for conveying powdered material. Flow rate shouldn't be too high either.

 

[sysrq]

According to readings it appears to be in star now cause 0.27kW motor in 415V star configuration has 115 ohm resistance and 0.18kW motor has 118 ohm resistance.

 

[sysrq]

Well theoretically if I set VFD Base Frequency (output frequency at which maximum voltage is
reached) at 25Hz and the max voltage is 200V, then 400V motor should maintain some torque at 200V (voltage/frequency ratio).
Torque demand might be low anyway cause it's a short helical feeder with gearbox for conveying powdered material. Flow rate shouldn't be too high either.

Sorry, my bad the right base frequency is 50*240/415 or 29Hz.
And in this case the motor power will be reduced from 0.180kW to 0.104kW.

 

[sysrq]

I think in industrial settings even low power VFD's for small motors should be with 3 phase input to reduce overall phase imbalance and increase power reserve. I don't know why have they bought several single phase VFD's.