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I have a motor with specifications:

  • star 400V
  • delta 230V

and motor is of course 3 phase. Now the question is, how can I connect the motor to delta connection if I have only 400V line to line voltage? Where can I get 230V line to line? Will I damage the motor in delta connection? Is delta configuration only meant to be using with VFD in that case?

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Now the question is, how can I connect the motor to delta connection if I have only 400V line to line voltage?

If you have 400 V, use the star connection. There is no reason to use the delta connection and the motor will draw too much current and overheat if you apply 400 volts to a connection designed for 230 V.

Where can I get 230V line to line?

There places in the world where 230 V, 3-phase is available and not terribly uncommon, but if you don't have it and have 400 V, there is no reason to find it.

Is delta configuration only meant to be using with VFD in that case?

The delta configuration is for people that have 230 V 3-phase. However you could use it with a VFD if you want to operate above the rated frequency. You could probably go 25% above rated frequency and voltage, but the motor bearings and rotor balance are probably not adequate for any speed higher than that.

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Now the question is, how can I connect the motor to delta connection if I have only 400V line to line voltage?

Wire the motor in star and connect it to your 400 V phase-to-phase supply.

Where can I get 230 V line to line?

You can't.

Will I damage the motor in delta connection?

Yes. You would be applying 400 V to a winding rated for 230 V.

Is delta configuration only meant to be using with VFD in that case?

No. It is meant for a 230 V phase-to-phase supply.

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    \$\begingroup\$ well, one could get a transformer that drops 400V to 230V, but it'd be a pretty expensive way to avoid just connecting the motor to 400V in a way that was already provided for. \$\endgroup\$ – TimWescott Oct 9 at 21:39
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If the motor is designed to run in star a 380V 3-phase power supply, then it cannot be connected in delta on the 'same' supply.

This is similar to applying 380 volt to 220 v windings so clearly the motor would fail.

The solution is either to get a 3 phase step down transformer to get 220 3 phase voltage and you need to calculate the ratings if the KVA of the transformer based on the load.

OR get an inverter, simply provide a 220V single phase (Line and neutral of the 380V supply) to it and get a 220V 3 phase.

Hope the answer is useful and clear

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