Single to three phase.

Besides the variable speed a VFD will give you full power, overload protection and prevent automatic restart after a power loss if you forget to turn the machine off. A static phase converter will only deliver 2/3 of the rated power. In this case the 1/2 hp motor would deliver only 1/3 hp. Do any of these things matter? You decide.
 
CluelessNewB said:
Besides the variable speed a VFD will give you full power, overload protection and prevent automatic restart after a power loss if you forget to turn the machine off. A static phase converter will only deliver 2/3 of the rated power. In this case the 1/2 hp motor would deliver only 1/3 hp. Do any of these things matter? You decide.
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people say this all the time...... I don't see any difference at all while running a motor with a VFD or a Static phase converter..... The only big thing I notice is the the VFD makes the loudest high pitched whining sounds and never stops.....
 
A very viable option I have not seen mentioned......

Back when I bought my first 3 ph machine I was told that using a static converter is basically single phasing the motor and that is why you get the reduced power. Due to this there are constant slight changes in the speed of the motor while it is coasting thru the phase that is not really powered and that shows up in the final finish of the part. For My shop I bought a large 5hp Rotary Phase Converter (RPC) and it powers all of the 3ph machines in my shop. My biggest machine is only 2hp, but I can have multiple machines running at the same time

The RPC is not as clean of power as a good VFD or true 3ph from the power company, but it is a lot cleaner than a static converter. I have a magnetic starter on the RPC so that if power goes out any and all machines stop and stay stopped. If you VFD you have to use a separate VFD on each machine. there is no running one VFD to power the whole shop. It also means looking at a new to me 3ph machine is not an issue because I already have power for it.
 
A static converter is no more than an appropriate capacitor connected internal to the enclosure, with the correct wires, or terminals, coming out. A "rotary" converter is a static converter with a 3 phase motor added to stabilize the output to nearer 120* phase rotation. Oh, and a start capacitor or single phase "kicker" motor to get it started. Both devices are as old as AC motor technology, and with a "flywheel" device to stabilize speed, steady enough for all but the most touchy operations.

A "Variable Frequency Drive", or VFD, is a derivitive of switching power supplies. The incoming line is converted to DC, with the AC (3 phase) synthesyzed from the DC buss. This could come from a series battery bank supplying 240 volts DC to the DC buss. I have seen such a device, an Uninterruptable Power Supply (480V UPS) large enough to start 500 HP worth of hydraulic pumps. I never needed to work on it, but did get acid burns when it blew up the batteries in 2005.

The newer (+/- 10 years) VFDs use a duty cycle synthesyzer to more nearly approximate a true "Sine Wave". Older versions use a "stair-step" synthesyzer, but the sine wave is not as close to a true sine wave as the newer versions. The stronger the attached magnetics, the more accurate the output. As in looking at the output with an O'scope but without a load shows significant "distortion". That really doesn't matter as the motor should always be connected.

For a grinder, there is a significant inertial load and the motor usually runs at 3600 (M/L) RPM. Less "slip" speed, where HP comes from. A static converter will work well enough there. As would a few "motor starting" capacitors in a DIY format.

.
 
Cooter Brown said:
The only big thing I notice is the the VFD makes the loudest high pitched whining sounds and never stops.....
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This seems to be a bigger problem with the super cheap VFDs like Huanyang. You may be able to change the carrier frequency parameter and eliminate or at least reduce the noise. Typically the higher the carrier frequency the lower the electromagnetic noise. Like everything there is a tradeoff, with higher carrier frequency you get more heat and possibly more interference with radios. Check your VFD manual for the parameter.
 
CluelessNewB said:
This seems to be a bigger problem with the super cheap VFDs like Huanyang. You may be able to change the carrier frequency parameter and eliminate or at least reduce the noise. Typically the higher the carrier frequency the lower the electromagnetic noise. Like everything there is a tradeoff, with higher carrier frequency you get more heat and possibly more interference with radios. Check your VFD manual for the parameter.
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I have an expensive one from automation direct.... My shop radio speakers hate this thing lol......
 
Cooter Brown said:
people say this all the time...... I don't see any difference at all while running a motor with a VFD or a Static phase converter..... The only big thing I notice is the the VFD makes the loudest high pitched whining sounds and never stops.....
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A 1/2hp grinder isn't exactly a powerful grinder, and now it's only a 1/3hp grinder. I sure can tell the difference between those two sizes in use. On bigger motors, and bigger machines it may not matter if you aren't pushing the machine hard, but something this small I wouldn't want to lose that much power. For light duty it might be fine, but that's not easy to pin down for someone else.
 
This is just a hobby. I'll just mainly be grinding 1/2" lathe tooling. I'm doing it now on a 1/3 hp bench top. Thanks for the input! I learned alot.
 
Cooter Brown said:
I'm tired of everyone "recommending" a VFD for every single piece of equipment.... This machine really wont from gain anything with a VFD.... Get a Static Phase Converter...... They are cheap, simple, easy to wire and they work!


www.ebay.com

HD 1/3-3/4 HP Static Phase Converter Mill Drill Saw USA MADE Single to Three | eBay

1/3 TO 3/4 HP STATIC PHASE CONVERTER. Bench grinder. Chop saw (1HP & under). Thickness planer. Amperage (Full Load & Single Phase)2.8. Table saw (2HP & under) Band saw (belt drive). Drill press (2HP & under).
www.ebay.com
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I hope you're right about this static phase converter, I bought this model off eBay (3/4 - 1 1/2 HP) from the same seller to power my DoAll ML band saw. Actually have two static converters for it. I read the manual which said it had a 1 HP motor and bought a 1 - 3 HP Phasematic off eBay. Then pulled the back cover on the band saw and found it actually has a 3/4 HP motor. My band saw has a blade welder which works off 220 single phase. I'm hoping when I wire the phase converter that I get the two pass-through wires in the converter correct for the welder. Here's the diagram I'm working off:

wiring diagram.jpg

My Bridgeport is on a static phase converter, 2 HP version so only seeing 1 1/3 HP. I've had no issues at all but I run on the conservative side for cutting aggressiveness (if that's a word). Figure the Phasematic will be a back up if the one on the BP ever fries.

I can't imagine stalling a bench grinder with a 1/3 reduction in power.

Bruce
 
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