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I have a challenge in connecting a 240 V, 3-phase, 9 kW machine to a 3-phase, 415 V supply in Uganda. The machine is from South Korea. The phase monitor trips.

Below is the brief precaution information for the installation of the machine

This equipment requires a lot of power consumption, so it must be installed in a dedicated line power source.

  • (AC 240 V, three-phase, 50Hz) Install in 9 kW or higher power line.

  • Equipment must be connected directly to the equipment through a dedicated switchboard.

  • Do not put a plug into the outlet.

  • Connect directly to a dedicated switchboard or distribution board.

  • Connect directly to the switchboard using the power cord attached to the equipment.

  • If the 3-phase power connection is not properly connected, the equipment will not work.

  • If the power line change message is displayed on the screen and the buzzer sounds, the power line connection is wrong.

The supply is 415 V.

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    \$\begingroup\$ Where's the photo of the motor nameplate? \$\endgroup\$
    – Transistor
    Commented Apr 7, 2019 at 21:46
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    \$\begingroup\$ Sounds like a job for a 3 phase transformer. \$\endgroup\$
    – Duncan C
    Commented Apr 7, 2019 at 22:11
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    \$\begingroup\$ I would also look at a possible VFDs to convert voltage and also reduce inrush power demand to reduce supply costs with a load that is now controlled ramp up V/f speed constant. Perhaps motor supplier can suggest., \$\endgroup\$
    – D.A.S.
    Commented Apr 7, 2019 at 22:23
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    \$\begingroup\$ Three phases of 240V gives you a maximum of 415V between phases. This is the correct supply for your machine. \$\endgroup\$
    – Finbarr
    Commented Apr 8, 2019 at 0:27
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    \$\begingroup\$ "phase error" could mean you have the phases in the wrong order, swap any two. \$\endgroup\$
    – Jasen Слава Україні
    Commented Apr 8, 2019 at 5:58

2 Answers 2

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The solution is to use an autotransformer with the following ratings:

Input: 3-N X 415 V ~ 50 Hz

Output: 3-N x 240 V 40 A

enter image description here

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One of these VFD's should meet your specifications if you provide all the inputs and outputs for Voltage, current with motor load specs. Send to various suppliers with your specs and expect some learning curve to setup many parameters for optimal operation.

The advantage of a VFD after setup is optimized is reducing the 300% to 500% starting induction motor ( if just one load) is reducing the surge power associated with AC motors as it spins up with constant torque using a constant ratio for V/f by controlling the startup ramp time if desired.

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