Three Phase Conversion using VFD

[joseph mansker]

For a very long time, I have resisted using three phase motors in my shop. I always removed the motors and installed new single phase motors and new motor starters. I bought a 1 hp Delta/Rockwell grinder at a school auction in February for $150 (because it was inexpensive and I really wanted it!) and finally got around to putting this tool in service. I researched and purchased a TECO/Westinghouse 1 hp VFD for $135 using 115v single phase input and converting to 230v three phase output. The process actually went pretty smoothly with a few mistakes made and corrected along the way. I mounted the VFD in an enclosure and then installed the enclosure on the shop wall, directly behind where the grinder is placed. I wired the 115v input cable and sourced from a nearby outlet. Fortunately, I already had a quantity of 4 conductor 10 gauge shop cord (overkill, I know, but its what I had) and used this for the three phase output from the VFD, wiring directly from the VFD to the motor leads. I had wired to the factory motor starter in the grinder stand but found that in my VFD documentation that the VFD output must be directly wired to the motor with no switches in series between the motor and the VFD. The manual provided with the VFD really wasn't helpful in the programming/startup process, so I called TECO/Westinghouse technical support and they were super helpful...had the grinder running in about five minutes. Really excellent customer service. Now I have a variable speed grinder that can handle some really challenging work.

So, would I do this again? Absolutely. Should have installed three phase sourcing long ago, could have saved myself some labor in the conversions...but oh well... Pictures are attached for the voyeurs in the crowd....:)

On another matter....I purchased a Mummert Dixon Oilstone Grinder at yet another school auction years ago and it has been lurking in a corner waiting for its restoration. I have plans to use it for plane iron and gouge sharpening...i have also attached pics...the stone cone which mounts on the front is not mounted in the picture, but I have several. Along with the grinder stones and leather honing wheel. Have any of 382563you ever se382564en one of these?382565382570382568382569382567382566

[Chris Parks]

. I researched and purchased a TECO/Westinghouse 1 hp VFD for $135 using 115v single phase input and converting to 230v three phase output.

Does this unit really step up the voltage because that is not a normal thing.

[joseph mansker]

Yes, it does step up the voltage. Stepping up voltage is entirely normal in the electrical distribution system that is in use in this country. We use step up transformers in switchyards and power plants all over the world. The VFD is not a step up transformer, but it accomplishes the same thing on a micro scale.

[Matt Day]

Lower hp vfd’s can use 110V line in, just don’t ask me why but it can. It’s preferable to use 220V from what I understand.

[Rod Sheridan]

A VFD that has a 120V input and a 208/240 volt output uses a voltage doubler rectifier to create a DC voltage that's a bit higher than the AC output voltage.

This is only done in small power applications because of the rectifier parameters.

For larger loads a transformer would be required..............Rod.

[Malcolm McLeod]

... Now I have a variable speed grinder that can handle some really challenging work.
...

Nice looking installation! How are you controlling On/Off, and speed? ...Do you just open the mounting enclosure and use the on-board keypad? (Don't see anything obvious in the pics.)


Does this unit really step up the voltage because that is not a normal thing.

Yes, it does step up the voltage. ...

Lower hp vfd’s can use 110V line in, ...

VFDs can step up voltage, but there are all sorts of limits: theoretical, practical, and software. I'll get beyond my knowledge base pretty quick on the theory, but I see some sources claim the 'increase limit' is the sq root of 2 (~=1.4X). So, supplying 120VAC to a VFD input, could yield a 168VAC ouput at 60Hz (less as the speed is reduced, of course). Others state it is theoretically unlimited. (Easy to google, so break out your IEEE-ish-ness, and decide which you trust.) Then practical limits get introduced by the simple fact that the output section (IGBT) of the VFD has to be 'off' for some fraction of each cycle. And finally throw in the manufacturer's software that may apply additional limitations, just so they don't have to replace the VFD every 3rd day (that whole 'warranty thing').

Bottom line I'd be very surprised if you can get a true doubling of the output voltage - - but I've never tried it, for the simple reason that I've never needed to. So, please take my (free) 'expertise' in this instance for what it's worth;).

Fluke site has a good reference for how to measure the voltage output of a VFD using their meters. Just in case you don't trust the VFD's on-board display?

*************
Edit: I get to spend the next 9 months commissioning 250-300 VFDs that range from 150Hp to 4000Hp (480VAC to 4160VAC).:cool::D Too bad they're not in my workshop.:(

[Brian Holcombe]

Using three phase was a mental hurdle for me, but now I think I would prefer 3 phase equipment in many cases.

[John Ziebron]

I restored a Logan (metal) lathe last year that has a 3/4 HP 3 phase motor. I was out of 220 volt breakers in my shop so I bought a Teco unit like Joseph that would convert my 110v single phase to 220v 3 phase. Teco, and I suspect other VFD manufacturers, only make 110 to 220 conversion VFDs for motors up to 1 HP. As Matt mentioned, it is preferable to use 220v input when possible but if the 3 phase motor is larger than 1 HP you have no choice.

VFDs work on the principle of controlling the frequency of the voltage pulse being sent to the motor, hence the name Variable Frequency Drive. There are many advantages of using a VFD and, with regard to frequency, one can program the high end frequency. VFDs typically come with the max frequency set at 60Hz which means your motor will run at it's rated speed. But most folks, like me, reprogram that max to 100Hz which is a safe setting. The high end frequency that one can set is really determined by the bearings in the motor.

Other advantages of a VFD are being able to program motor start and stop times, and remote control of certain functions like start, stop and forward/reverse. There is a lot of information on VFDs on line and YouTube videos. And the tech guys at Teco, as Joseph mentioned, were very helpful when I had an issue. Here is a picture of my remote control box with those functions. The readout on the remote is an inexpensive unit that comes with a small Hall effect sensor and magnet.

[joseph mansker]

Malcolm,
Thanks for the compliment. I am using the VFD keyboard and the potentiometer to control on/off and speed. I used the enclosure to keep the VFD isolated from dust and debris that might be generated from the grinder. I am mindful of the heat generated by the VFD so will be checking to assure temperatures don't get out of control. Another shop issue to deal with. I recently obtained a Grizzly air filtration unit that I have installed above my table saw to help reduce fines in the air to improve the overall safety of working in an enclosed environment.

[Bill Dufour]

In North America 120 volt circuits are normally limited to 15 or 20 amps. So 120 volt input vfd's are limited to 1-1.5 horsepower input.. This limits the output to the same 1-1.5 hp. IF you want more horsepower it is cheaper to double the voltage using the same wires and double the available horsepower.
If that is not enough you need to pull new bigger wires and you might as well use 240 at that point. I have never seen a single pole breaker bigger then 30 amps.
Bil lD.

[Rod Sheridan]

Hi, single pole breakers are common to 50 amperes....................Rod.