Looking for 20hp VFD anyone selling?

Bill D said:

Location? Farmers use big VFDs for irrigation pumps. Probably too big for you.
Bill D

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stephen thomas said:

What size is it?
# heads?
Work alone or with employees?

Not to argue with go big or go home, depending on your needs, my experience might or might not be useful.

First thing to understand is that widebelt sanders are abrasive limited.
There is only so fast, or so deep (trade-off) they can go efficiently per each abrasive grit, modified slightly by the substrate. Poplar going a slight bit deeper or alternately, faster, than hard maple on the same grit. Pine sometimes being more difficult because it clogs the belts, as does bloodwood. IOW, the sander takes only a modest amount of power to start since it is not under load. Then it might seldom if ever need all the power on tap, if the abrasive is used the way it should be for accurate work (reliable calibration), efficient throughput, and cost effective life of the abrasive.

As an aside, to use a widebelt efficiently, the platen should not be in use except for fine finishing, say 120 grit and above. It has no use and is a power & maintenance drag on coarser grits. It corrupts calibration efforts for which only the contact drum should be in use.

My 25" x 72" (not a typo, it is pre-75" standard) RAMCO came with 30 HP on it, which i could not run. But there was a 15HP here which i swapped on, and continued to run for the past couple decades off the 7-1/2HP installed shop built phase convertor (Idler motor, cap start). Ignoring the possibility of running a separate phase convertor for the sander alone, i did not want the cost of idling a big convertor for the rest of my shops needs the other 90% of the time when the sander was not in use.

This includes running the 15HP sander, adding the 2HP Torit cyclone after the sander starts. A 9HP tablesaw can be started and used in addition either before or after starting the sander. (the more motors idling, the better the power balance in the sytem) Separately, the 7.5HP will start and run the Diehl lumber jointer (550v transformer, 3 heads = 15HP + the Torit running full tilt). I have run these combinations for flooring jobs with an employee. The machines were not idling. The only time there has been a problem was running Wenge & similarly hard/dense flooring full width on the sander at 60grit with an employee to off-bear. Throughput for that has to be reduced on hot days. Working alone, i've never overloaded it.

The phase convertor is only generating one leg.
Size all wiring for the big loads, and protect it with correct 3ph breakers.
Protect all motors individually at the starter, within the normal operating limits.
If you don't have at least one employee paid to push the limits in production as you work together, you might never notice the phase convertor is "underpowered"

BTW, as often related in the past, the pole pig across the street blew twice. The second time, NYSEG sent an engineer to inspect my shop system. Then instrumented the house and shop for 30 days during a period when i had to get a flooring job out (production). The engineer found nothing wrong, was impressed with the set up, and later relayed that the problem had been NYSEG's. When i upgraded the house from 60A pull fuse service to a 200A panel and notified them to come out and hook up to the service entrance & set the meter in the hub, they ran new cables from the existing transformer but never changed it beyond the original service. After the inspection/instrumentation period they sent a crew around to actually install the bigger transformer to better match what had been paid for earlier.

Point is, always comply with all safe wiring practice and protection devices. Within that construct, starting motors with minimal load takes little comparative HP. So the adage to use twice the HP idler for the motor being run is prudent but often unnecessary overkill. (Unless a compressor is being run on the same circuit). In use, analyze how often you will ever use -true- "full load amps" above the idler motor rating. Quite a few of those amps are by-passing the idler on the way to the driven motor, anyway. The more motors idling in the same circuit, the more uniform it is. If there is trouble starting a given machine, letting say the TS idle with the blade below the table can make it easy to start other machines, and acts as a second idler. I originally wired in a station with mag starter to add a second idler to the generated 3ph panel, in case 7.5 idler was not enough. Have not ever needed to use it.

Good luck.

smt

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FREISEN said:

Man I wish I had the knowledge about this stuff you seem to have. I am pretty out of my depth when it comes to anything involving designing electrical set ups and how to use what. I started as a hand tool guy and just got into bigger machines. My shop is single phase and I have 1988 37" timesaver that is three phase with a 20hp motor and 5hp feed motor. I'm trying to figure out a way to run it and keep it all under $5k if possible.

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