How I put a VFD on a drill press for no more belt changes

With several recent threads about VFDs, I thought I’d share how I equipped a drill press with a 3-phase motor and VFD to avoid needing to change belts.

First, the drill press: a pretty junky Taiwan-era Delta that I picked up for $75 on craigslist. It hadn’t been used very much, though, and had almost no measurable slop in the quill. It got stripped down, completely repainted, and put back together (this is the before picture, obviously :) )
http://imgur.com/O6kDDtk.jpg

Next, the motor. I found an old 3-phase motor in the “junk box” at work (so it was “free”). It’s a 200V, 2HP, 1725 rpm motor. It also got stripped apart, repainted, and new bearings installed. It’s probably much too big for this application, but it was free, so I’ll work with it.

http://imgur.com/1RJDqoB.jpg

Then, the VFD itself. Trying to be thrifty, I picked up a no-name “ebay special” shipped-from-China VFD for $100 (including shipping), rated for 2HP. Additionally, this VFD had a remote-mountable control panel, and a built-in speed adjustment pot, which I wanted.

http://imgur.com/TXjxfkC.jpg

The VFD I bought also supported “space vector control”. To explain the value of this, we need a quick detour to motor drive theory: When a VFD varies the frequency of the output, it also varies the amplitude of the voltage. Most VFDs increase the voltage proportionally to the speed, and this is called “V/Hz” control. This is done to maintain constant magnetic flux within the motor, and since flux is what produces torque, it results in constant torque over all speeds. However, power is speed times torque. If torque is constant as speed is varied, it results in very low power at low speeds, and full power only at full speed. For something like a drill press, we likely desire plenty of power at low speeds (for large diameter cutters), so this is undesirable.

One way to overcome this is to simply use a larger motor. In this case, I’m doing that, already. The larger motor will produce more torque at a given speed than a smaller motor, and that, alone, may be sufficient to get enough low-speed power. However, another method of increasing power delivery at lower speeds is to deviate from V/Hz control and use space vector control, instead. The one sentence explanation of space vector control is that it uses current sensors to actively monitor the 3-phase currents and adjust the pattern of switching of the transistors to produce more torque at low speeds.

I hooked the motor to the VFD and programmed the various parameters. Of note, since the motor is only rated for 200V, I needed to program a 200V limit into the controller (since the supply voltage is 240V). I also needed to program several other motor nameplate parameters into the controller and let it run a “tuning” algorithm to “learn” the motor parasitic parameter values in order to use the SVC mode.

Unfortunately, this motor was physically much larger than the 3/4HP motor originally installed, and the mounting plate didn’t align in any way with the holes on the new motor.

http://imgur.com/f6t5OTU.jpg

I ended up fabricating a replacement out of some aluminum (note: this is probably the only part of the project I was disappointed with: the aluminum wasn’t stiff enough and the motor sags a bit).

http://imgur.com/xyLHBDM.jpg
http://imgur.com/hOTsFEj.jpg

With the motor mounted, I removed the center (idler) pulley, mounted a new sheave to the motor shaft, and used a link belt to connect to the remaining sheave.
http://imgur.com/xQOWaZF.jpg


I mounted the control panel of the VFD in the space previously occupied by the on/off switch – luckily, it fit almost perfectly, and a little black RTV filled the small gaps around it.

http://imgur.com/qjygTby.jpg

A RJ-45 cable runs from the control panel to the VFD, which is located in a small metal box near the base of the drill press. This control cable and the power cord for the motor are held together in a piece of looming that keeps the cords neat.

http://imgur.com/PYd8sMS.jpg

The VFD offers the ability to display various parameters while running. One very useful parameter is “load speed”. It also offers the ability to set a “load speed multiplier” to adjust for any pulley ratios, etc, that might be in the system. Mine is thus configured so that, when running, it displays the actual speed (in RPM) of the chuck. A turn of the knob on the control panel runs it from zero to 3,000 rpm. Pressing the “stop” button brings the chuck to a standstill in 1.0 seconds (also a programmable value).

http://imgur.com/wVb3wxZ.jpg

My total investment in this project is <$200 (which is obviously because I got the motor for free, but 1-2HP 3-phase motors can often be had very cheaply, anyways).

I was worried about the reliability of the VFD, but I believe even the no-name VFD manufacturers are using control ICs from reputable chiphouses, and the transistors in these drives come in a “pack” of 7 (6 for the 3 phase, and 1 for braking resistor) that are also sourced from reputable vendors. The VFD manufacturer is merely adding a user interface and mechanical packaging.

Anyhow, hope you enjoyed this. I’d be glad to answer any questions.

I've cursed the tangle of belts on my drill press for years. Thanks for posting this fix.

Nice job Dan, I put a VFD and 3 phase motor on my General 340 press last year and I had a 2 hp motor initially as it was the size that fit the pulley and was in the rathole. At the suggestion of a friend I set the current limit of the VFD as if it were a 1 hp motor so all I get is 1 hp, because I really didn't want 2 hp on the 340, I have a bigger press for larger drilling tasks where I can clamp the work securely and give it more torque.

I have since sourced a 1 hp motor for the 340 so the 2 hp motor is back on the shelf. Sure is handy having digital speed control on the press and I did the same with my wood lathe.

That's a good idea, Erik - I may need to put a current limit on mine, too. I've noticed that with larger-diameter bits (forstners, etc), I can EASILY get so much power at ~300rpm that the belt slips or the keyless chuck becomes impossible to release without some channel locks :)

That really an inspiring project. I've wanted to do something similar for quite a while. Good job.

Mike

As a lover of VFDs, ( I have 7 in use now and two more almost ready to go), my only concern it the box that has the VFD in it. They do produce heat and need ventilation. I mount mine high and out of the way like in the photo below.
CPeter
Attachment 351224

Well done Dan, nice project.

It is some times a good idea to keep the old mechanical drive in tack. that way you don't need the full range from a drive . the motor and drive like a range of about 30hzs at the low end and thats plenty for woodworking drill presses , after that the power and toque drop off. it maintains a good motor speed for cooling to. Often you don't want high toque and so setting the VFD to a lower hrz in a higher speed pulley gears lets you do sensitive work like tapping threads without snapping the tap. Also higher gears and over running the motor to say 2 times speed or 120 hzs get the spindle up to 10,000 rpm for cutter router bits. you need the right chuck but i do this on mine . I wounder if you set the base frequency on your drive for that 200 volt motor? not all drive can do this. 200 volts is not a common 3 phase voltage and is out side your house hold range. Any plans for external switches.

Good point, Jack. It wouldn't have hurt to leave the belts. In my case, the drill press gets little use, to begin with, and with such a big motor, I'm not worried too much about cooling. I also never ever ever want to touch one of those belts, again :)

This is plugged into a 240V (RMS) single-phase supply, and since it's using SVC, I don't think I need to explicitly set a base frequency. It's programmed not to exceed 200V output (which I have confirmed works properly), and other than that, the SVC algorithm takes care of adjusting the voltage to whatever is necessary for the given frequency.

Dan.

I also have a 200 volt motor that needs a VFD.
Where did you order yours from?

Thx.

Fred

Quote:

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Originally Posted by Dan Friedrichs

Good point, Jack. It wouldn't have hurt to leave the belts. In my case, the drill press gets little use, to begin with, and with such a big motor, I'm not worried too much about cooling. I also never ever ever want to touch one of those belts, again :)

This is plugged into a 240V (RMS) single-phase supply, and since it's using SVC, I don't think I need to explicitly set a base frequency. It's programmed not to exceed 200V output (which I have confirmed works properly), and other than that, the SVC algorithm takes care of adjusting the voltage to whatever is necessary for the given frequency.

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Dan has nothing to do with RMS its got to do with the Volt /Hzs relationship. More than likely you have provision to set the base frequency in the motor overload section . on that drive for that motor if base frequency is not set than the only time that the voltage and Hzs are in sink is at 72hzs assuming your voltage is 240. the vector control will not operate properly if base is not set. you don't need to limit the motor to 200 volts what you need is to set base so that the relationship to volts is the same at 200 as it is at 240 volts . in your case you would set base to 72 hzs. that is because at 200 volts that motor likes 60 hzs so you have a ratio of 3.3333volt to 1 hz.

proper math is in the PDF

http://controltrends.org/wp-content/...ndamentals.pdf

Jack, I don't know what you mean by "voltage and Hzs are in sink".

I think what you mean is that most VFDs maintain a constant V/f ratio, in order to maintain a constant value of magnetic flux (because the amount of flux is determined by the quantity of volt-seconds applied to the motor). Increasing the voltage without increasing the frequency proportionally will result in more magnetic flux, which may magnetically saturate the motor. Thus, to avoid magnetic saturation (essentially "short circuiting" the motor), many VFDs maintain a fixed V/f ratio. You're suggesting that I need to program the VFD to use a V/f ratio of 200V/60Hz. Normally the "base frequency" is the actual rated frequency of the motor (60Hz), but in this case, since I'm running a 200V motor off 240V, I need to "trick" the VFD into producing the correct V/f ratio (200/60) by telling it that the motor is rated for 72Hz (because 240/72 = 200/60).

I agree that you are correct if this were a V/f drive. However, when using sensorless vector control, the V/f ratio is NOT constant. The frequency is set by the operator (ie - I turn the knob to set the desired speed, and the drive sets the electrical frequency to produce that), and the voltage amplitude is determined by an algorithm. There is no need to maintain a fixed V/f ratio, since the drive measures the actual current, separates the current into the magnetizing and torque-producing components, and adjusts the timing and amplitude of the voltage to maximize torque.

So I believe the only parameter I need to set is the maximum voltage (200V). The only reason to maintain fixed V/f is to avoid magnetic saturation, and since this drive contains current sensors which monitor the 3-phase output, it knows if it exceeds the magnetic saturation threshold without having to merely rely on a "hard" V/f limit. This is why SVC allows greater low-speed torque.

Quote:

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Originally Posted by fRED mCnEILL

Dan.

I also have a 200 volt motor that needs a VFD.
Where did you order yours from?

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Fred, here's the one I bought:

http://www.ebay.com/itm/361155386082...%3AMEBIDX%3AIT

It might be too small for your 3HP motor, though. Based solely on the appearance, I'd guess the Amazon one you linked in the other thread is probably by the same manufacturer.

Quote:

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Originally Posted by Dan Friedrichs

Jack, I don't know what you mean by "voltage and Hzs are in sink".

I think what you mean is that most VFDs maintain a constant V/f ratio, in order to maintain a constant value of magnetic flux (because the amount of flux is determined by the quantity of volt-seconds applied to the motor). Increasing the voltage without increasing the frequency proportionally will result in more magnetic flux, which may magnetically saturate the motor. Thus, to avoid magnetic saturation (essentially "short circuiting" the motor), many VFDs maintain a fixed V/f ratio. You're suggesting that I need to program the VFD to use a V/f ratio of 200V/60Hz. Normally the "base frequency" is the actual rated frequency of the motor (60Hz), but in this case, since I'm running a 200V motor off 240V, I need to "trick" the VFD into producing the correct V/f ratio (200/60) by telling it that the motor is rated for 72Hz (because 240/72 = 200/60).

I agree that you are correct if this were a V/f drive. However, when using sensorless vector control, the V/f ratio is NOT constant. The frequency is set by the operator (ie - I turn the knob to set the desired speed, and the drive sets the electrical frequency to produce that), and the voltage amplitude is determined by an algorithm. There is no need to maintain a fixed V/f ratio, since the drive measures the actual current, separates the current into the magnetizing and torque-producing components, and adjusts the timing and amplitude of the voltage to maximize torque.

So I believe the only parameter I need to set is the maximum voltage (200V). The only reason to maintain fixed V/f is to avoid magnetic saturation, and since this drive contains current sensors which monitor the 3-phase output, it knows if it exceeds the magnetic saturation threshold without having to merely rely on a "hard" V/f limit. This is why SVC allows greater low-speed torque.

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I don't see any function to set voltage . In fact the drive states that its is only for 220 to 240 volts .

i take it this is your manual.

http://www.hclub.ee/download/varia/K...0119(V1.1).pdf

just trying to help out and would like you to get the most from your drive.

found this on page 79

http://i284.photobucket.com/albums/l...pst6p5f8wv.jpg

i am just a woodworker with about 15 drives in the shop so maybe those with more knowledge can comment? does Mr Norton get out much anymore? been year! but he does know his singa faze and tree faze,

Yes, that's the manual. It's confusing because the drive supports both V/f control AND vector control.

http://i.imgur.com/ihBO5rc.jpg

In vector control, the max voltage (and other parameters) are set in this table:

http://i.imgur.com/RFNqUs5.jpg

Note that you only have to input parameters 0-4. Parameters 5-9 are automatically calculated when it performs the dynamic auto-tuning.

I looked through the manual, and couldn't immediately find a way to set the frequency differently if V/f mode was desired, though.

Quote:

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Originally Posted by Dan Friedrichs

Yes, that's the manual. It's confusing because the drive supports both V/f control AND vector control.

http://i.imgur.com/ihBO5rc.jpg

In vector control, the max voltage (and other parameters) are set in this table:

http://i.imgur.com/RFNqUs5.jpg

Note that you only have to input parameters 0-4. Parameters 5-9 are automatically calculated when it performs the dynamic auto-tuning.

I looked through the manual, and couldn't immediately find a way to set the frequency differently if V/f mode was desired, though.

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V/F is still vector! its used to running more than one motor at a time. V/F in not volts/hzs. For auto tuning to be usefull motor inputs have to be correct . D0-01 is model dependent and this one is lacking .

Quote:

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Originally Posted by jack forsberg

V/F is still vector! its used to running more than one motor at a time. V/F in not volts/hzs. For auto tuning to be usefull motor inputs have to be correct . D0-01 is model dependent and this one is lacking .

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Respectfully, I think you're misinformed about this. "V/Hz" and "V/f" are both used interchangeably to refer to a control mode where the ratio of volts to hertz (or "frequency") is constant. People often call this "scalar" control. "Vector" control does not use a fixed ratio of volts to hertz. It adjusts the voltage as needed to maximize torque.

Here's a good article I found that explains it:
http://machinedesign.com/motorsdrive...ol-method-vfds

Sorry, I accidentally clipped off the header at the start of those tables. The column containing the phrase "model dependent" has a header that reads "Factory setting". So they're just saying that the default value of d0-01 varies, depending on which specific model of the drive you buy. You can program d0-01 to whatever you want.

Quote:

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Originally Posted by Dan Friedrichs

Respectfully, I think you're misinformed about this. "V/Hz" and "V/f" are both used interchangeably to refer to a control mode where the ratio of volts to hertz (or "frequency") is constant. People often call this "scalar" control. "Vector" control does not use a fixed ratio of volts to hertz. It adjusts the voltage as needed to maximize torque.

Here's a good article I found that explains it:
http://machinedesign.com/motorsdrive...ol-method-vfds

Sorry, I accidentally clipped off the header at the start of those tables. The column containing the phrase "model dependent" has a header that reads "Factory setting". So they're just saying that the default value of d0-01 varies, depending on which specific model of the drive you buy. You can program d0-01 to whatever you want.

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is this the part that got clipped off?

http://i284.photobucket.com/albums/l...psrec4rjiz.jpg
So D0-01 is not capable of 200 volts even though it can be entered as a value in the setting.

there are other modes for V/F that use torque compensation that adjust the voltage as i said for more than one motor. that's why you have a function on your drive for base frequency. I did not see one place in that manual that said the the VFD in sensor less vector did not need the base set when the motor was out side the VFD input voltage. Please Inform me i am clearly confused .

I can't find that text in the version of the manual I have, but I also don't understand what you're saying. Are you saying you don't think the output voltage can go below 220VAC? That's clearly wrong - the output voltage must go down to near zero when the frequency goes to near zero.

Setting D0-01 to 200V and running in SVC mode clearly limits the output voltage to 200V. I've ran the motor up to the voltage limit, and it definitely stops increasing at 200V (as shown on the display and verified using an oscilloscope). When I change D0-01 to other values (ie - 180v, 190v, 200v, 210v), the voltage also stops increasing once it hits those values.

Torque compensation is just slightly "nudging" the constant V/Hz ratio at different speeds to give more favorable performance for a particular load curve. It still relies on a constant V/Hz ratio.

SVC does not use a constant V/Hz ratio, so setting a "base frequency" makes no sense. It won't limit the output voltage because the output voltage is not related to the base frequency!

I want to be very clear that I think you're completely correct, Jack, about how to set up a V/Hz drive to allow running a 200V motor off a 240V supply - I agree with you, entirely, there. But those are not vector drives. These new vector drives do not operate the same way.

I don't know how I missed this thread but, Jack and Don you both right. In V/H there is a constant line between volts and hurts. When your hurtz are at 50%, so are your volts. In most applications this would be OK.

In higher torque applications at lower speed/hurtz you should be using a sensorless vector mode (this is open loop).This maintains the voltage(better) and hurtz varies more. This keeps in the flux in the amateur stable with torque requirements. The motor actually works more like a DC motor.

On a drill press that is drilling metal and I am running a 1.5" drill bit at 45 RPM with power feed of .005 per revolution i'd like to know my horse power is up there. This would be applicable for lathes, Tablesaws running a smaller dado blade, milling machine, bandsaw... almost anything that you want the rim speed or surface speed to have constant torque.

If the VFD only has V/H at 50% hz. you have just De-rated the motor 50% of its horsepower and it is linear.

I think if you put this https://www.amazon.ca/dp/B003GUH4SC/...WHPFVFGE2RE3EK
And gave it a good pull at 800 RPM you'll see a trip.

It is definitely an interesting topic. I think running a "only" V/H inverter needs to be considered and weighed out for the application.

I can't remember the last time I changed the belt on my Delta drill press...too lazy I guess! This is pretty cool stuff, Dan. I'm an EE but lacking in 'motor' skills.... :)

Quote:

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Originally Posted by Chris Padilla

I can't remember the last time I changed the belt on my Delta drill press...too lazy I guess! This is pretty cool stuff, Dan. I'm an EE but lacking in 'motor' skills.... :)

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See, that was my problem, too, Chris - "Set to 2k RPM? Sure, that'll probably be fine for this circle cutter ;)"

More correctly, V/f (or V/Hz) pattern is the generic term for the software parameter which can be set to Open Loop Vector, Closed Loop Vector, Constant Torque, Variable Torque, Auto Torque Boost, Multi-Point V/f Custom Curve Setting, and other manufacturer specific operation modes.

Constant torque produces a linear output voltage to frequency curve that provides increased current (torque) at low speeds. Variable torque produces a non-linear curve that provides energy savings for pump and fan operation. Vector control modes monitor output current and motor speed if available and adjust output frequency and voltage to maintain the desired shaft rpm or load current.

Other than some rare, esoteric configuration, the first five parameters in the table above should reflect the motor nameplate data. Base frequency (d0-03) should be set to the synchronous speed of the motor (60Hz). The auto-tune function uses these parameters to set limits of operation and performs electrical tests that enable calculation of the motor electrical parameters.

Single or multiple-motor operation can be accomplished in most output modes, but it gets dicey in vector control mode if the number of connected motors changes considerably. (Think hot-strip steel mill cooling table with 50 motors on the same drive.)

As an aside Dan, I would be careful about running your control and power cables is such close proximity. Your manual may specify precautions. Locating low voltage signal cables and motor output cables together is a big no-no. VFD input cables are less noisy, but can occasionally be problematic.

Interesting factoid: Tektronix consulted with our company for the development of the PWM triggering functionality in the classic PS 222 portable scope.

As a time out from the discussion I am enjoying, I wanted to say, Dan you did a really nice, clean install! I just surface mount the VFD anywhere that seems convenient but it always feels half done... for a week then I move onto other projects.

BTW no offense as these discussions are useful and interesting to me but those that are only considering VFD for 3 phase woodworking machines might should steer clear it is easy to get the impression it takes a EE with concentration in motor theory to take advantage of VFDs where the reality is for our needs only the basic functionality is needed and you won't need to track down your neighborhood EE nor pay the local teenaged hacker to get you up and running with the correct amount of electrons running the correct direction and riding the sine roller coaster on the correct track. Again not suggesting it shouldn't be discussed, as it should be, but just some words to hopefully avoid scaring the bejeebus out of someone.

Quote:

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Originally Posted by Dan Friedrichs

See, that was my problem, too, Chris - "Set to 2k RPM? Sure, that'll probably be fine for this circle cutter ;)"

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I don't even know what mine it set to, Dan, but I've run EVERYTHING at that RPM. You may have just piqued my curiosity enough to look but I bet I'll forget when I get home.... LOL :D

Very nicely done Dan! That enclosure doesn't appear to be NEMA, how does someone determine if they need a NEMA enclosure or the VFD can survive in the shop conditions without?

Nice setup, but my understanding of 200V motors is that they are rated that so that they can be run continuously on 208, 230 or 240V. Over-voltage isn't a problem for most motors, but under-voltage (without current control) is.

Thanks Dan! Perfect timing for me as my single phase DP motor just quit. I'd like to go the 3 phase/VFD route for variable speed as well. I plan to purchase the same VFD you have. When I go to purchase the 3 phase motor, does it really matter what speed/rpm I get?

Looks like a NEMA 1 enclosure to me.

Quote:

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Originally Posted by Bill Adamsen

Very nicely done Dan! That enclosure doesn't appear to be NEMA, how does someone determine if they need a NEMA enclosure or the VFD can survive in the shop conditions without?

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Quote:

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Originally Posted by Mike Brucker

Thanks Dan! Perfect timing for me as my single phase DP motor just quit. I'd like to go the 3 phase/VFD route for variable speed as well. I plan to purchase the same VFD you have. When I go to purchase the 3 phase motor, does it really matter what speed/rpm I get?

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I'm not sure it really matters. You'll need to outfit it with a pulley, so by sizing that (and choosing which step on the other pulley), it seems like you could adjust for different motor speeds. My impression is that 1725rpm might be a better choice just given the relative pulley sizes you have to deal with.

Quote:

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Originally Posted by Bill Adamsen

Very nicely done Dan! That enclosure doesn't appear to be NEMA, how does someone determine if they need a NEMA enclosure or the VFD can survive in the shop conditions without?

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If NEMA was needed... I think a UL on VFD would be too (as well.. Final inspection on set up) . I don't think this set up meets UL requires.

Quote:

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Originally Posted by Bill Adamsen

Very nicely done Dan! That enclosure doesn't appear to be NEMA, how does someone determine if they need a NEMA enclosure or the VFD can survive in the shop conditions without?

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Quote:

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Originally Posted by Frank Pratt

Looks like a NEMA 1 enclosure to me.

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Quote:

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Originally Posted by Matt Mattingley

If NEMA was needed... I think a UL on VFD would be too (as well.. Final inspection on set up) . I don't think this set up meets UL requires.

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NEMA type-ratings run from 1 to 13 with several sub-catagories defined by adding letters (i.e. '4X'). Most smaller VFDs are designed with the intent that they are going to be integrated into a MCC (motor control center) or a control panel (enclosure). The MCC or control panel would have it's own NEMA type rating - suitable to the installed location. Since the 'integrated' VFD is thus protected from the environment, the VFDs are typically built to a NEMA-1 standard, intended only to protect personnel from incidental contact with live electrical parts (sometimes called 'finger-safe').

To enclose a NEMA-1 VFD, I would recommend a NEMA-12 enclosure as a minimum for a professional woodworking environment, but as with all things, it will cost extra.

I haven't read the manual for Dan's VFD selection, but a quick look at the photo makes me think it is NEMA-1. In a hobby setting, it will do fine with minimal care (use clean, dry air to blow the heat sinks, fan, and circuit boards clear of any dust accumulation). Biggest thing is protect it from water drips or spray. But all said, I'd grab a cheap NEMA-12 box and be done with it.

Edit: Putting a NEMA-1 VFD inside a NEMA-1 enclosure, certainly provides some extra safety margin, but I'm not sure it improves the NEMA rating for purposes of code compliance. ...I'd have to do some more research on that:confused::confused::confused: And very neat install Dan - I want one!

All that stuff is way beyond me. When I added a VFD I started with a 3450 RPM 3 phase, 1.5 hp motor. Had dog squat power at low RPM and could stall the motor by grabbing the chuck. I played around with the belting and finally switched to a 1725 RPM 2 hp motor. With the right belting I ended up with satisfactory low RPM power. I sacrificed a fit of high RPM, but never used it that much anyway.

I hung the VFD in back below the motor. The VFD has a pop-out control that can be remote mounted with the proper cable, but I didn't see to have immediate access to all those functions. So I just put a speed pot, a run switch, and tach up front. With a separate tack, I don't need to worry about slipping, etc. It is still not perfect but does what I need.

http://www.ncwoodworker.net/pp/data/500/DP-7.JPG

http://www.ncwoodworker.net/pp/data/500/DP-6.JPG

http://www.ncwoodworker.net/pp/data/500/DP-8.JPG

Very interesting and informative thread. I am also lazy switching belts and hate doing so. Recently was doing research for myself to do similar conversion. I'm still not clear about motor choice. From what I gathered, it seems to me that in order to get great torque at low speed one needs inverter duty motor, which can handle low frequency well. Standard and especially older motors will not work that well under VFD.
Is it true? What you thought experience on that matter?

Quote:

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Originally Posted by Yuri Sadykov

Very interesting and informative thread. I am also lazy switching belts and hate doing so. Recently was doing research for myself to do similar conversion. I'm still not clear about motor choice. From what I gathered, it seems to me that in order to get great torque at low speed one needs inverter duty motor, which can handle low frequency well. Standard and especially older motors will not work that well under VFD.
Is it true? What you thought experience on that matter?

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A 'inverter duty' motor is not mandatory. You can use nearly any good quality 3-phase motor with a VFD.

Sometimes you can experience problems with the motor overheating, due to inadequate air flow. This can occur IF you run for extended periods at low RPM - typically below 25% (15hz) of the rated motor speed. As always, every user is different. How long? How slow? What load? All these weigh into the mix.

Dan may have already worked thru this, but I'd be tempted to leave all the normal sheaves on the DP, and set the belts to run at ~1000 RPM at the quill. And then leave them alone.

Now install a VFD. At 25% VFD output, I'd have virtually no concerns about overheating, I have decent torque (see Dan's OP), and I'd get ~250 RPM (suitable for 2" or so Forstner).

At 100% output, I get full torque and ~1000 RPM.

This 25%>100% range, would cover 95% of the work I do.

For short runs, I can drop to 10% output (100 RPM).

On the other end of the scale, most VFDs can be configured to run at up to 300% of 'rated' RPM; a few to 600%. So with the same set-up, I can get up to 3000 RPM. Motor bearings take a beating, but again, for limited runs this will work.

I'm now able to cover 99.9% of the work I do. For the once-in-a-lifetime needs, I can move the belts (:confused:assuming I remember how:confused:).

Yuri,

I am not an engineer but have a number of VFD in my hobby shop and none are on inverter duty motors. As far as duty is concerned, the motors I have are not being pushed too hard. I have a 1 hp on the drill press, and 1.5 hp on the lathe and speeds are not fluctuating wildly and neither motor is being employed in a 24/7 severe basis as a pump, compressor or HVAC unit would be. While an inverter duty motor would be the gold standard, my hobby usage is unlikely to ever result in motor damage.

I agree with Erik and Malcolm. Especially on drill presses, where the "duty cycle" is very low and the mechanical load is very low, I think you'd be hard-pressed to do anything "wrong" - it will work fine. Maybe in continuous, demanding applications it would matter, but not here.

I could have left the step pulleys in place, as Malcolm suggests, but in my case, the bore in the step pulley wouldn't fit my new motor, and step pulleys are much more expensive than singles. So I just bought the single.

Malcom,
thank you for the input. I use my drill press (Delta 17-965) in my hobby woodshop. No prolonged usage, so my concern about overheating is minimal. I want some range in rmp. High rpm (let say ~2000) for drilling with small drills with very low torque requirements. Low rpm mostly for hole saw/drill, forstner bits, occasional thread tapping. Basically, standard set of operations.
Main thing I need from the motor is that it should be capable to work at 25% or less of rated RPM. I read somewhere that standard (older especially older) will not work at all at 1/3 or even 1/2 of normal RPM.

I can buy that bundle (motor with VFD) ~$300
http://dealerselectric.com/three-qua...t-Package-.asp
where motor Features:
· NEMA MG1-PART 31 Inverter Duty 15:1 Constant Torque
· Service Factor 1.15
· IP55 degree of protection
· VPI Impregnation
· Internal Tropicproof
· F1, F2, & F3 convertible
· Class F insulation
· Dual Rated 60/50Hz
· Warranty: 3 Years
· CSA approved for Class I ; Division 2 ; Groups A,B,C & D,T3

though I can save $100 for the bundle if I just pick up standard/older similar motor.

Quote:

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Originally Posted by Yuri Sadykov

Main thing I need from the motor is that it should be capable to work at 25% or less of rated RPM. I read somewhere that standard (older especially older) will not work at all at 1/3 or even 1/2 of normal RPM.

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This is not completely true. I'm not exactly sure what you're considering "older" but ideally it comes down to cooling. It really depends on its design. If it is a
2 pole (3600 RPM)
4 pole (1800 RPM)
6 pole (1200 RPM)
8 pole (900 RPM)
10 Pole (720 rpm)
12 pole (600 RPM)
16 pole (450 RPM) these are all numbers at 60 Hz (what the power company presently is giving us in North America)
A typical 4 pole (1800 RPM) Motor can run at double the speed and usually the bearings are rated for 5000 RPM-ish and the built-in fan is doing the job it's therefore. Now if you take the same motor and run it at half speed 900 RPM with a full load torque the windings and Armature will start overheating causing breakdown of bearings, Greece, breakdown of winding shellac, linear expansion of armature... and the list goes on. But if you can adequately cool the motor with an additional fan, you can achieve rpm in the 10% range. Sensor less Flux vector VFD's work better in the situations.

Quote:

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Originally Posted by Yuri Sadykov

I can buy that bundle (motor with VFD) ~$300
http://dealerselectric.com/three-qua...t-Package-.asp
where motor Features:
· NEMA MG1-PART 31 Inverter Duty 15:1 Constant Torque
· Service Factor 1.15
· IP55 degree of protection
· VPI Impregnation
· Internal Tropicproof
· F1, F2, & F3 convertible
· Class F insulation
· Dual Rated 60/50Hz
· Warranty: 3 Years
· CSA approved for Class I ; Division 2 ; Groups A,B,C & D,T3

though I can save $100 for the bundle if I just pick up standard/older similar motor.

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Now my drill press has a 5 hp motor. What would be your suggestion? this question is open for anyone to answer. What would be the cheapest VFD single phase input (non-D-rated) three phase output that has sensorless vector control?

Quote:

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Originally Posted by Matt Mattingley

Now my drill press has a 5 hp motor. What would be your suggestion? this question is open for anyone to answer. What would be the cheapest VFD single phase input (non-D-rated) three phase output that has sensorless vector control?

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Here's a 2HP example with SVC for $110:
http://www.ebay.com/itm/361155386082...%3AMEBIDX%3AIT

You really have a 5HP motor on a drill press?


Also, I have a really strange question: Why do people keep typing "D-rated"? I've never seen that, before (I mean, everyone I know writes "derated"). Is it common shorthand?