# Max Rpms?



## wawoodman (Oct 12, 2015)

I have my Rockwell mill 3-phase wired through a Hitachi VFD. Today, for the first time, I thought I would take the time to check machine rpm on the different pulleys at different settings on the pot.

The slower 4 pulleys worked fine, right through the range (max of about 1750 rpm.) But when I got to #5 (of 6), when I got about halfway through the range, the machine cut out and the VFD showed an error code. I reset it, and tried a couple more times. Same result.

I'm guessing that the machine is receiving the same amount of current; only the pulleys are different. So why might it be cutting out?

That having been said, I doubt that I would need much more speed unless I'm using 1/4" mills in aluminum. Still it would be nice to have a higher top end, just in case...


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## JimDawson (Oct 12, 2015)

I would first check the setting on your VFD to make sure the output amps and volts matches the motor name plate data.  The error code (and it's meaning) would be helpful in troubleshooting this problem.

Is this happening at a setting less than 60 Hz?  You may not be able to run at greater that 60 Hz at higher belt ranges.
.
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## wawoodman (Oct 12, 2015)

I'll check that tomorrow, Jim, and post a follow-up. thanks.


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## wawoodman (Oct 13, 2015)

Here's a little more info. 

Motor: 1/2 HP, 3 phase, 1140 RPM, 60 cycle

Input power: 220V, 60 cycles (AFAIK)

Inverter: Hitachi SJ200

When I run the motor on the four slower pulleys, all is well. If I run it under NO LOAD, it runs fine at top speed. If I put the belt on either of the high speed pulleys, it will run for a short period of time, and then shut off, with one of two error codes: 

E05: Overload protection>When a motor overload is detected by the electronic thermal function, the inverter trips and turns OFF its output
E07: (one time only) Overvoltage protection>When the DC bus voltage exceeds a threshold, due to regenerative energy from the motor

Looking at this in the cold light of morning, it suggests to me that the machine spindle may be slightly restricted; just enough to cause a little drag at the high speeds. I may just have to stay away from those higher outputs.


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## tcarrington (Oct 13, 2015)

Both of the error codes could be caused by your accel and decel times. On the higher pulleys the reflected load has a higher rotary inertia. Said another way, it takes more energy to bring the spindle to a higher RPM. The overload might be eliminated by increasing the accel time and the overvoltage error eliminated by increasing the decel time. The overvoltage can also be tamed with a brake resistor. As mentioned earlier, do check the motor name plate and make the SJ200 parameters match.


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## JimDawson (Oct 13, 2015)

When you installed the VFD, did you set the parameters to match the motor?  especially the max current?


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## wawoodman (Oct 13, 2015)

I honestly don't remember. I will have to look through my paperwork, or, go through the programming to check.

I was walked through the setup by someone on one of the forums, but again, I don't remember his name.


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## wawoodman (Oct 13, 2015)

Looks good! I checked the output, and it was set to 60 cycles. But the start/stop times were set to 1 second. I'm sure I did that, but I don't know why, unless I was going to power thread. I reset the times to 10 seconds (the original defaults), and now I can get ALMOST to top speed. I can live with that.

Thanks, gentlemen.


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## JimDawson (Oct 13, 2015)

Happy to hear it's up & running OK.


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