Question about VFDs - Woodworking Talk - Woodworkers Forum
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post #1 of 9 Old 06-04-2020, 05:59 PM Thread Starter
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Question about VFDs

What are some of your experiences with converting single phase to three? I am looking to run a 2hp 3ph 700rpm motor from 1950. Is a VFD a good option? would I have anything to worry about with the age of the motor? Any advice would be of great help

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post #2 of 9 Old 06-04-2020, 06:21 PM
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For our CNC I use a Hitachi VFD from Drives Warehouse in Dallas. Call them and ask if it's a viable option.

My initial response is that this would not be a good application. Does the current application require variable speed? How much is a single phase 2 HP motor? You can also get less expensive VFD's on eBay, btw. In some cases you'll lose some power using a VFD, as well.

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post #3 of 9 Old 06-05-2020, 04:22 AM Thread Starter
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No variable speed is required just looking to convert single phase to three. I would like to try and get another motor, its a 32in northfield band saw direct drive. I will have to see how easy it is to find another motor that is compatible.

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post #4 of 9 Old 06-05-2020, 02:01 PM
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When you are below 3 horsepower, VFDs are typically cheaper than other options. These 2 distributors carry several low cost VFDs to choose from.


https://www.factorymation.com/ac_drives_qs


https://www.automationdirect.com/adc...cy_drives_(vfd)
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post #5 of 9 Old 06-06-2020, 08:54 AM
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I think VFDs are great. I currently am only running one, on my vertical knee mill, 1ph. I have one on a 1941 Rivett 1020 with a 2ph motor (which I've sold to a good friend). I installed them on two Bridgeport vertical knee mills for a patternmaker friend, one 2hp, the other 3hp. All were TECO FM50. All were set up for variable speed and reversing operation. I've never felt there was any significant loss of power. The ability to run my mill down to almost no revolutions and instant reversing is an extremely valuable feature. Allows me to do rigid tapping.

Installing the FM50s has been easy, once I'd done it once, but there was a bit of learning curve. An installation without speed control or reversing would be a snap. One "trick" is that VFDs do not like external switching, so the On/Off switch of the bandsaw would have to be rewired to route it through the VFD. Terminals are clearly marked, though, so it isn't difficult.

One thing to consider is that VFDs usually like 220v input rather than 110V, although there have been 110V units available.

The FM50 series is now discontinued. The replacements are the FMX TD200 series. I've not done one of these, but believe they would be similar.

If your 1950 3hp motor is in good working condition, I see no reason why it would not work just fine.

I would be interested to hear more from David about why he thinks a VFD would not be a good application. While not taking advantage of the variable speed or reversing capabilities, it would allow operation of the bandsaw with full power without having to replace the motor.

Rick

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post #6 of 9 Old 06-06-2020, 11:33 AM
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Quote:
Originally Posted by RickKr View Post
I would be interested to hear more from David about why he thinks a VFD would not be a good application.

Rick
I misspoke, Rick. Multitasking and responded too quickly; I was thinking about a static convertor where you lose about 30% power. A VFD and rotary phase convertor allow you to run at full power.

And not having priced 2HP single phase motors recently I just figured the cost to get the VFD and set it up would just about be the same as buying a new motor but the VFD I got is the Hitachi and its cost is higher than some that some that have been linked here. But again, it was a shot from the hip so my aim may have been off on both counts.

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post #7 of 9 Old 06-06-2020, 02:29 PM
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VFD's work great, but if you are really going to work it hard the motor should have class F insulation, but that being said I have ran motors with class C and D and put many hours on them


The first VFD's I worked on used vacuum tubes for diodes, when a drive went down I would just take all the tubes out and that them the the then Revco drug store where they had a kiosk that had a tube tester and replacement tubes LOL


Or you can also built a rotary converter you will need a 3 phase motor at least twice the size of the one you are driving preferably a 2 pole, or 3450 RPM, hook L1 and L2 to the ballast motor, and then hook L1,L2&L3 from the driven motor to L1,L2,&L3 of the ballast motor. You will need a method of getting the ballast motor spinning before applying power, but the ballast motor will create the third leg. It will be a weird voltage but I have been running my Axleson 7 1/2 hp engine lathe with this setup for over 25 years


If you look on Youtube you ought ot be able to find a video describing it better then I have

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post #8 of 9 Old 06-06-2020, 02:31 PM
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No worries, David. Actually, I'm glad you mentioned the rotary phase converter. That is another good option. Perhaps more expensive and they can take up floor space. I have one for my Monarch 10E metal lathe. 5hp phase converter runs off 220V, runs a 3-phase AC motor, which turns a DC generator to run a 3hp DC motor that drives the lathe. Speed is controlled by a rotary dial on the front of the lathe. One of the more reliable drive systems for the Monarch 10EE lathes.

Faced with this need, I would choose the VFD. Rotary phase converters add noise as well as often taking up floor space. The VFD can go right on the side or top of the machine.

Rick
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post #9 of 9 Old 06-06-2020, 03:58 PM
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A VFD puts out better three phase then a rotary, plus if you run the machine a lot a rotary isn't very efficient besides taking up the room


I just posted building a rotary because if you have a source for used 3 phase motors it is the cheapest way to go, but now they have VFD I think that will go to 10 hp from single phase


I have a 100 amp Phase Perfect digital converter that puts out better power then the utility company delivers, I used it on a Hypertherm Hydef plasma cutter, but it was about $12000 when I bought it
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