Hi a have a multitool machine running a 3 phase, 380V motor with two speeds through a switch (0,37 Kw and 0,51 Kw). Since i only have 220v at home a bought a frequency converter, that can do that. The inverter i bought is a "FR-S520SE 0,75K" (the datasheet into the link)

The wiring of the motors looks like this : enter image description here I am confused how to connect the motor to my inverter ?, since i have - as you can see in the picture - 6 wires coming out of the motor and going into the switch

  • \$\begingroup\$ See comment on previous question about checking with a competent supplier, that this one can supply a 380V motor. They will have the answer to this as well as how to connect. Otherwise, find a more competent supplier. \$\endgroup\$ – Brian Drummond Jan 20 '17 at 19:51
  • \$\begingroup\$ i am sorry what question are you reffering too ? \$\endgroup\$ – mounim Jan 20 '17 at 20:48
  • \$\begingroup\$ electronics.stackexchange.com/questions/280091/… \$\endgroup\$ – Brian Drummond Jan 20 '17 at 21:24
  • \$\begingroup\$ ah i see .. well i did, what it was advised, since the other model was not suitable. i got an inverter with the specification mentioned. the problem now is just how to wire it \$\endgroup\$ – mounim Jan 20 '17 at 21:50

Connect a Transformer Between VFD and Motor

You can use a VFD that accepts 240 volts, single-phase input and provides up to 240 volts, three-phase output. You will need to connect the VFD output to a three-phase 240 to 480 volt step-up transformer. You could use three single-phase transformers. You can use a 480 to 240 volt step-down transformer and hook it up "backwards." Adjust the VFD so the output only goes up to about 190 volts.

Connect the VFD to the Switch

You can connect the output of the VFD to the switch. You should not operate the switch while the VFD is running, but you can use either switch setting. Using the low-speed setting will give the motor more torque and also prevent having to turn the frequency too low. The transformer may saturate, draw excessive current and overheat if the frequency is turned too low.

Connection Diagram

enter image description here

A 240:480 V 60 Hz transformer will provide some margin of safety regarding saturation of the transformer with the VFD output. A 240:480 V 50 Hz transformer will provide less margin. A 220:380 V 50 Hz transformer will provide no margin and may force you to operate the motor at a reduced voltage.

Direct Connection To Motor

You could connect the VFD directly to the switch if you adjust the VFD to put out 220 volts at 30 Hz. You could operate the motor up to a little more than half speed that way. You might be able to operate close to full speed with greatly reduced torque.

  • \$\begingroup\$ Will work. But don't you think a boost mode VFD would be cheaper? \$\endgroup\$ – winny Jan 20 '17 at 20:45
  • \$\begingroup\$ i already bought this inverter "FR-S520SE 0,75K" .. i am just nt sure how to connect it \$\endgroup\$ – mounim Jan 20 '17 at 20:47
  • \$\begingroup\$ @mounim Oh, if you already have it and can't swap the motor to a 220 V one, a transformer might be the cheapest option. \$\endgroup\$ – winny Jan 20 '17 at 21:18
  • \$\begingroup\$ @winny ... the inverter should work, i am just not sure how to wire it, since i have 6 wires from the motor \$\endgroup\$ – mounim Jan 20 '17 at 21:51
  • \$\begingroup\$ @mounim You will not be able to use the center tap arrangement with your VFD. Find which windings are used for full speed. \$\endgroup\$ – winny Jan 20 '17 at 21:55

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