VFD Mystery: Why’s My Spindle Overheating & Shutting Down?

Hello! I've picked up loads of knowledge on this forum but problems with my home CNC build lead to my first post.

I'm trying to configure my Mitsubishi VFD (FR-D720S-100SC-EC) with my G-PENNY air-cooled 2.2KW 220V spindle (GST2.2C-80-24K), but I must be getting something wrong, as the spindle is drawing too much current, getting very hot, and the VFD is cutting the power. I don't want to kill the spindle, hence looking for advice on VFD parameters. Is this the right place to ask?

I also posted on CNCzone and asked the spindle manufacturer, but I probably went into too much detail because I didn't get any responses yet :smile:

Thanks in advance for any guidance.

Hi @Spurtle, welcome to the community!

Yep, you’re in the right place for this sort of question, and you’ve definitely done the right thing by asking before letting the magic smoke out of that spindle. The G-PENNY 2.2 kW units run happily on the Mitsubishi FR-D720S, but only if the parameters match the spindle’s nameplate.

A mismatch will cause exactly what you’re seeing, high current draw, excess heat, and the VFD cutting out.

For reference, here’s a parameter map that works well for a GST2.2C-80-24K air-cooled spindle (400 Hz, 220 V, ~8 A rated) on the FR-D720S-100SC-EC:

Code:

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Parameter No. Setting Description

Pr.3 400.0 Hz Base frequency – matches spindle rated frequency
Pr.4 400.0 Hz Maximum output frequency
Pr.7 10.0 s Acceleration time (extend if overcurrent trip persists)
Pr.8 10.0 s Deceleration time (extend if DC injection braking is too aggressive)
Pr.9 8.0 A Motor rated current (check spindle nameplate)
Pr.14 220 V Motor rated voltage
Pr.72 10.0 kHz Carrier frequency (reduces audible noise – adjust for VFD heat)
Pr.75 2 Control mode: 0–10 V analogue speed control
Pr.79 2 Voltage/frequency pattern – constant torque (suitable for spindle)
Pr.150 400.0 Hz Upper frequency limit
Pr.151 0.0 Hz Lower frequency limit
Pr.152 400.0 Hz Multi-speed high limit (if used)
Pr.157 400.0 Hz Jog frequency (optional)

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I've stuck those in a table attached to this post, so you can take them to the machine with you.

Notes:

• Cooling: Try not to run much below ~6000 RPM for extended periods; air-cooled spindles rely on fan speed for cooling.
• Trips (E0L2): If it still trips on start, bump Pr.7 (accel time) up a little until the trip stops.
• Check the nameplate: G-PENNY 2.2 kW spindles are often labelled 8.0–8.5 A; set Pr.9 accordingly.

Once you’ve set the above, you should see the current stay within spec and the spindle run cooler.

Let us know how you get on, I'm sure a few here run the same or very similar combo and can help fine-tune if needed.