Hitachi VFD Connection

Hey Michael, hey Moosa @moosaes,

Here you mix up input current and output current!

Also according to IEC 60034-1 the power rating on spindles does not mean the electrical power they draw, but the mechanical power they are able to deliver at their shaft (see here for details).

Yes, with a VFD on a single phase supply circuit, the input current is about is more than twice what is the rated output current. I own the Omron MX2 which is identical to your Hitachi WJ200, the manual is practically identical too (Omron MX2 User’s Manual / Hitachi WJ200 User’s Manual).

As you can see on the VFD’s nameplate that Michael shows above, it delivers max. 12 A three-phase output current to a spindle motor, and in order to do this, it draws up to 24 A on a single-phase supply line. In the manual, a 30 A fuse/MCB is recommended. That is because the output current rating applies to three phases that are delivered on three wires simultanely, each rotated by 120°. If you look at mathematics of three-phase electricity, you can calculate how much current that is if you sum up all the three currents at a certain moment in time:

Image: Three-phase electricity: Each wave is shifted by 120°.

A VFD is an AC-to-DC-to-three-phase-AC inverter, which means, first the AC input current from the supply line is rectified to DC power, then it is stored in a large capacitor, and then an array of six IGBTs controlled by a microcontroller switches the three output currents on and off to form the three output current waves on the fly.

That also answers the other question: The table in the Omron MX2/Hitachi WJ200 manual that says you have to use 10 AWG on both input and ouput is obviously wrong for the purpose of simplicity. This table has only one column “Power Lines”, but to be correct, it would need to have two columns for the power lines, one for input power wire and one for output (motor) power wire, at least for the single-phase input models.

– Source: Omron MX2 User’s Manual

Image: A typical spindle cable for use in a power chain (LAPP ÖLFLEX® CLASSIC FD 810 CY)

You need the 10 AWG cable only on the single-phase input (suited for 24 A), not on the (motor) output. For the VFD output, i.e. the spindle cable, 12 AWG is enough, as the current is spread over three wires (suited for rated VFD output, which is 12 A here). See nameplate of VFD. As you can see here, the nameplate of my Omron MX2 for 2.2 kW motor and single phase input is identical regarding input and output power to Michael’s Hitachi WJ200:

Image 1: Michael’s Hitachi WJ200 VFD nameplate.
Image 2: Aiph5u’s Omron MX2 VFD nameplate.

As you can see, the input and output currents on my VFD and on Michaels VFD are identical:

50–60 Hz 200–240 V 1-phase input: 24 A / 22 A,
.1–400 Hz 200–240 V 3-phase output: 12 A / 11 A.

The only difference is that the Omron MX2 can deliver 580 Hz instead of only 400 Hz on Michael’s Hitachi WJ200. So my MX2 can run a spindle like this: ATC-8022-42-HSK25 2.2 kW 42,000 rpm water-cooled spindle at 34,800 rpm (see also[ ➪ How to calculate the rpm of spindles based on frequency)

If you want to calculate what your spindle really draws, see here:

It shows what a 2.2 kW spindle really draws and that the power ratings on cheap chinese spindles are often wrong.

See also the explanations in

to be sure to select the correct spindle cable and its dimensions.

The Masso G3 CNC controller does not support Modbus serial communication. You’ll have to use the analog 0–10 V control for spindle speed and a programmable input terminal for spindle RUN/STOP/REV. Use the search function to find:

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