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Pairing VFD with table saw motor

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Forum topic by joeIWD posted 08-03-2020 09:50 PM 441 views 0 times favorited 12 replies Add to Favorites Watch
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joeIWD

18 posts in 641 days


08-03-2020 09:50 PM

On Wednesday, I am picking up an 80’s era Powermatic 66 that has a 3PH 5HP motor. I don’t have 3-phase in my home garage so I will need to convert it. If I go with a static converter like a phase-a-matic, it is cheaper but I drop to 3.3 HP which should still be plenty for the 8/4 stock I work with and would be able to keep the existing on/off switch.

The VFD option is nice since it will keep all 5HP at the blade even though this is way more than I need. It has the downside of having tiny on/off buttons which are inconvenient to use compared to the standard switch. Based on the motor plate, the FLA in 230V 3PH mode is ~14 amps. I have read some people go with 2X of the FLA rating on the motor. Is this necessary?

I am looking at using this VFD for my saw. [https://www.ato.com/5hp-vfd](https://www.ato.com/5hp-vfd)

Thanks for your help


12 replies so far

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MrUnix

8211 posts in 3047 days


#1 posted 08-03-2020 11:10 PM

Very few people actually operate their machinery using the VFD buttons. For your table saw, you can use your existing control station (start/stop switch). As for the VFD in question… I would be suspicious as the model specified is not listed as a valid model in the manual, and as with pretty much all current VFD’s, 3hp (~10-11A output) is the largest that will accept single phase input without having to de-rate the output. The manual for the VFD you show lists the same pattern, with the largest single phase model being the GD3500-2S0022 at 10A rated output using 220Vac single phase input.

I personally would just go with a reputable brand name 3hp VFD from a local supplier that can provide support should you need it. You may want to visit the practicalmachinest site for some of the stories, both positive and negative, regarding some of the cheap no-name imported models. Just my 2c.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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GrantA

2852 posts in 2256 days


#2 posted 08-04-2020 12:34 AM

Funny you post this today, I just took some pics of my 66 to list for sale. Mind telling what you paid for this one?
Brad, while the VFD is a fun option and adds a nice brake, the single phase input (and corresponding output cap) is going to choke the motor a bit anyways. $90 for a us made super simple static converter starts sounding a whole lot better and you’ll still net about 3.5hp
All my VFDs are ABB and I highly recommend checking with Wistex

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joeIWD

18 posts in 641 days


#3 posted 08-04-2020 12:52 AM

I paid $1080, 52” fence in good shape, motor cover and dust door. Not sure if it has the miter gauge. Serial number indicates 1984

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GrantA

2852 posts in 2256 days


#4 posted 08-04-2020 01:13 AM

Nice, mine is a 1985 I think (serial ends 1985) and has the same fence but the motor cover is missing. You’ll love it!! I’m not 100% sure I even want to sell it but now I have 3 bigger tablesaws and a little unisaw ugh

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MrUnix

8211 posts in 3047 days


#5 posted 08-04-2020 02:43 AM

Brad, while the VFD is a fun option and adds a nice brake, the single phase input (and corresponding output cap) is going to choke the motor a bit anyways. $90 for a us made super simple static converter starts sounding a whole lot better and you’ll still net about 3.5hp
- GrantA

The VFD adds a lot more than just braking and will run the motor at full power. I’m not sure where you get the idea that it will choke the motor. A static converter will run the motor at reduced power, and unbalanced – so it will run hotter, which can lead to premature failure.

Plus – the price of VFD’s have come down to the point that they are very cost competitive. A name brand VFD can be had for ~$200 and provide a bunch of features that is not possible any other way. You also will no longer need the stock starter that shipped with the machine, so you can sell it to recover a good hunk of what you paid for the VFD.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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GrantA

2852 posts in 2256 days


#6 posted 08-04-2020 02:56 AM

I’ll have to look at my PM66 motor but a similar 5hp Baldor that I have handy calls for 12a at 230v 3phase. If you can only feed it 10-11a you’re limiting power, right?
I didn’t think about the unbalanced load, again I love my VFDs I just was questioning if it’s really the best choice for the OP.

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MrUnix

8211 posts in 3047 days


#7 posted 08-04-2020 03:27 AM

I ll have to look at my PM66 motor but a similar 5hp Baldor that I have handy calls for 12a at 230v 3phase. If you can only feed it 10-11a you re limiting power, right?
- GrantA

Nope. You are looking at the FLA of the motor, which a table saw motor will rarely, if ever, reach. And most modern VFD’s can sustain up to 150% of rated output for short periods of time, typically 60 seconds or more. There are plenty of users running their 5hp machines on “3hp” VFD’s… here is one such example:

5 HP 12/14 saw with 3 HP VFD; Rusty's bench started.

And that is on a Delta 12/14 machine that not only has a 5hp motor, but is swinging a much larger blade as well. There are plenty of examples out there, so it’s certainly not a unique situation.

Cheers,
Brad

PS: You can date powermatic machines using the serial number, but it’s not the last 4 digits… you can visit the magic decoder page here: Powermatic Serial Numbers over at the Vintagemachinery site

-- Brad in FL - In Dog I trust... everything else is questionable

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GrantA

2852 posts in 2256 days


#8 posted 08-04-2020 03:34 AM

Good deal then carry on! Keep us updated OP with what you do and how you like it!

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Jared_S

396 posts in 807 days


#9 posted 08-04-2020 02:28 PM

I’m a fan of the fuji frenic series vfd, (I have 6 currently) they are relatively inexpensive, reliable and well documented. The single phase 3hp has a 12 amp output.

Yes its more than $200 but not much.

I’m running that same model 3hp drive on a 5hp 16” jointer, and a 5.5hp shaper. Both are in the 14FLA range.

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joeIWD

18 posts in 641 days


#10 posted 08-05-2020 09:41 PM

I got the saw today and couldn’t be more excited! I am going with a teco-westinghouse L510, VFD
Everything is in pretty good shape, some tightness on the bevel wheel and height adjustment wheel, but that’s to be expected. I’m going to pull the motor tomorrow and take to a motor shop to have a look. Second order of business is to take it all apart and to the sand blaster. I’m keeping the paint and stripes original.

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Matt

35 posts in 2815 days


#11 posted 08-17-2020 02:57 PM

I just picked up a Unisaw from late 70’s, early 80’s… It has a 3phase 3hp motor. Looking at installing a VFD as well. I’m curious how it is going for you so far?

-- Matt, Pennsylvania

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joeIWD

18 posts in 641 days


#12 posted 08-17-2020 03:45 PM

I haven’t picked up the VFD just yet, I have been spending lots of time on tearing things apart and stripping paint. I am buying the Teco Westinghouse L510-203-H1-U today from wolf automation so hopefully that will come in soon. I will let you know, but lots of people suggest the Teco Westinghouse L510 and Fuji Freneric are good options for this size motor. Hope that helps.

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