VFD fundamentals

[Susquatch]

That is interesting. What is the size of your cabinet? I have mine mounted in a repurposed fire alarm cabinet with ventilation holes in the bottom and top and have never had any issues with heating. I use the same cabinet for my RPC controls.

Like so many things of this nature, "It depends."

How fast, or even if, a device will overheat depends on many factors. Insulation factor, heat conductance factor (heat sinks), convection (air flow volume), enclosure size, duty cycle, load, other loads, etc etc.

With things that depend on so many factors, I prefer to measure worst case temperatures and let that decide what I need to do to prevent problems.

 

[PeterT]

Here are some pics & specs. 215 to 3250 spindle rpm range based on belt/sheave combos. Jeez, maybe I should just get my butt in gear & shimmy up there more often. Belt move is a bit inconvenient but not difficult. Anyways looks like 1725 rpm, 1/3 HP moor. I don't see anything that defines the mount bolt pattern or shaft so I'll have to examine that more closely.

 

[deleted_user]

Here are some pics & specs. 215 to 3250 spindle rpm range based on belt/sheave combos. Jeez, maybe I should just get my butt in gear & shimmy up there more often. Belt move is a bit inconvenient but not difficult. Anyways looks like 1725 rpm, 1/3 HP moor. I don't see anything that defines the mount bolt pattern or shaft so I'll have to examine that more closely.

If you installed the 3600 rpm motor I previously linked to you could leave the belts set at the ~2:1 reduction 820 rpm.

At 60Hz you'd get 1714 rpm.

You can turn down the motor to 4 HZ where the motor would be turning at ~240 rpm and the belt reduction would give you 114 rpm.

You can easily run at 120 HZ and get 3428 rpm.Most VFDs can go higher on the HZ frequency too.

But you could also change the belt to high speed, run the VFD at 120 HZ and get 13,392 rpm.

 

[thestelster]

Baldor General Purpose TEFC motors with the Super-E designation, are classed Inverter Ready in their literature, but they have a 20:1 turndown ratio. Their Inverter Duty motors are 1,000:1, but start at 5HP and $3,500.00, ouch!!

 

[deleted_user]

Baldor General Purpose TEFC motors with the Super-E designation, are classed Inverter Ready in their literature, but they have a 20:1 turndown ratio. Their Inverter Duty motors are 1,000:1, but start at 5HP and $3,500.00, ouch!!

Baldor are over priced.

Plenty of sub 5 HP motors with 1000:1 turndown in the $450 - $600 range. The way to find them is search for Inverter only motors

 

[PeterT]

If you installed the 3600 rpm motor I previously linked ...

This one?

Personalize

Is it a call/email for price sort of thing?

Is there a good cross reference site I can plug in frame spec, for example 56C, it shows corresponding dimensioned drawing?

Looks like IMP shaft/key. Now I'll have to see what I actually have.

 

[YYCHM]

I didn't realize this was so complicated LOL....

RF30 Basement Install

So after much dithering I finally decided to convert my mill to 3 phase with VFD speed control. Pretty much have everything I need now 2 HP 3 PH motor $60 from Kijiji 4 HP VFD $75 from Amazon ESD switch $18 from BB 12' of 14AWG 4 strand electrical cord $23 from Home Depot I was going to...

canadianhobbymetalworkers.com

 

[PeterT]

CT means Constant Torque (range) right? Just for interest I went back to the EMWI website where they showed prices, sub-category knife grinder machine motors. Bigger HP but it was a convenient collection. There is a slight price dif between 10:1 & 2:1, but not particularly huge. Is there an application or reason why one would not want high CT?

 

[deleted_user]

This one?

Personalize

Is it a call/email for price sort of thing?

Is there a good cross reference site I can plug in frame spec, for example 56C, it shows corresponding dimensioned drawing?

Looks like IMP shaft/key. Now I'll have to see what I actually have.

The code 56C denotes frame size indication and type variation. A 56 frame size motor will have a dimension from the rotor shaft centreline to the underside of the motor feet of 3 ½” and a shaft diameter of 5/8”.

The C suffix relates to a motor with a type C face mounting and in the case of a 56C motor frame the distance from the mounting location shoulder outer face to the shaft end is 1 7/8".

 

[deleted_user]

CT means Constant Torque (range) right? Just for interest I went back to the EMWI website where they showed prices, sub-category knife grinder machine motors. Bigger HP but it was a convenient collection. There is a slight price dif between 10:1 & 2:1, but not particularly huge. Is there an application or reason why one would not want high CT?

Im sure there is a reason, but I dont know it.

 

[Brent H]

Some info you you guys:

https://controltrends.org/wp-content/uploads/2010/10/VFFundamentals.pdf

 

[PeterT]

I can see lathe motors being a being different animal. They typically have a relatively heavy flywheel (the chuck) to get moving & slow down. And maybe upper RPM limits based on bearings/heat regardless of what the motor can spin? I don't even know.

A drill press has a small mass chuck/tool. Just guessing, higher RPMs reserved for smaller cutting tools (therefore load). Lower RPM, maybe more/constant torque would be good, like hole saws, bigger drills maybe more challenging materials? Tapping heads are clutched anyways but maybe medium load? Then on the drill press there is the choice of sheave/belt position that I guess would be your middle ground of expected plus minus rpm range.

Maybe for knifemaker belt grinder guys, 10:1 is a good compromise? They are direct drive vs geared & probably some maximum SFPM dictated by abrasive belt. I know even less about those applications. Is lower RPM for more control = less removal rate, or coarser belts & high removal rate? I see these videos where they demo the range of tick-over low to high speed range, but when it comes to cutting always seems like med/high RPM & its more about the the belt grit selected for application? But I'm digressing to yet another project n my wish list.

 

[Mcgyver]

Is there a good cross reference site I can plug in frame spec, for example 56C, it shows corresponding dimensioned drawing?

Hi Peter,

Do a search for "nema frame size" and you'll readily finds chart from which to match your dimensions. Here for example :https://www.grainger.com/know-how/equipment-information/kh-nema-frame-guide

I like your DP's counter shaft giving the low speed range. My Buffalo DP is one stage and the lowest speed is 580, I find it a bit hairy when using a tapping head so usually don't, which is sub-optimal. The flip side is speed changes are so easy, just grab the belt and move it.

I'm also thinking of converting mine to 3P and VFD. Slow speeds is imo where drill presses underwhelm but getting the slow speed is useless without power. Low speeds are needed for running a large drill or taping at a controllable speed is what my lacks (yours is kind of already there imo @ 215) so I plan on going with a 1725 motor. Going with a high rpm motor negatively impacts low speed power. Not sure I see the point of a high speed motor, if you think the rest of machine is up to it, you can always run the lower rpm motor over 60 Hz. Really though, are you going to need more than 3200 on that machine? if the answer is yes, imo you need something like a servo drill press. If the need for speed is really there, you're going to need high precision, balance, sensitivity. concentricity etc beyond what a larger DP offers. By starting with a lower speed motor, at tapping speed/large drill speed (say 2/3 - 1/2 reduction), there still should be enough power left.

As a VFD provides for low voltage controls, one I idea I have is to rig up a kill switch on a kick plate, basically a foot actuated e-stop. With one hand holding the work/vise and the other on the feed, a way to kill the power quickly if you feel something going wrong would be a good thing. In adding a VFD to a DP, it might be something to consider planning for in the wiring.

 

[Brent H]

Since you guys are going deep into the VFD world…..

Setting up the programming:

Max Voltage: 220 V for typical motor
Reference Frequency: 60 Hz for our motors or 50 Hz for Euro

Intermediate Voltage - default is 110 - What is this? Appears to be just half the motor max voltage but does it have a purpose?

Intermediate frequency: 25 Hz is default- again what is this? It is half the working frequency- does it have a purpose for adjustment?

Minimum voltage: 0 - what does increasing it do?

Minimum frequency: 0 - what does increasing it do?

Maximum operating Frequency: default is 65 but could be set to yield your maximum desired RPM.

Minimum Operating Frequency: 0 default but could be set for your slowest RPM.

There are tons of codes you can program- any ones that should be fixed up? or that there is a benefit to changing? - Working frequency, revolution for 50 Hz for example.

 

[Susquatch]

Since you guys are going deep into the VFD world…..

Setting up the programming:

Max Voltage: 220 V for typical motor
Reference Frequency: 60 Hz for our motors or 50 Hz for Euro

Intermediate Voltage - default is 110 - What is this? Appears to be just half the motor max voltage but does it have a purpose?

Intermediate frequency: 25 Hz is default- again what is this? It is half the working frequency- does it have a purpose for adjustment?

Minimum voltage: 0 - what does increasing it do?

Minimum frequency: 0 - what does increasing it do?

Maximum operating Frequency: default is 65 but could be set to yield your maximum desired RPM.

Minimum Operating Frequency: 0 default but could be set for your slowest RPM.

There are tons of codes you can program- any ones that should be fixed up? or that there is a benefit to changing? - Working frequency, revolution for 50 Hz for example.

Hi Brent. My manual is useless on all those questions. I played with them anyway. One of my many character flaws I guess...

What I discovered is that they DON'T do the obvious. Some of them seem to make no difference. Others totally screw up sensorless vector mode - not good. Still others cause the motor to not spin up properly on its own.

I ended up resetting to factory and starting over leaving all of those alone. But even this is a problem because factory default is NOT what they say it is. So I had to painstakingly go through everything.

If you decide to play with them, keep a log so you can reverse whatever you did. But I'm not really sure that works because some settings change others and then don't reverse when you change them back.

I'm still waiting for a call back on auto tuning function. The tech I spoke to couldn't get his head around "yes it works but I want it to work optimally". He wanted to close the file the moment I said it works. Obviously not wired the way that I am.

I opened Pandora's box when @Dabbler convinced me to get a VFD. Now I wanna know what else is in that box..... LOL!

If you have a TECO, here are my current settings. They do work great.

Set 00-00 from 0 to 1 - Sensorless Vector Mode

Set 00-02 from 0 to 1 - use external switch for R/S & Attach SPDT switch to common, S1, & S2

Set 00-05 from 0 to 1 - External Potentiometer & Attach 2K pot to 10V, Gnd, and AVI (Ctr to AVI)
Note - my VFD Recommends 5K pot but other ranges will work. I didn't have a 5k so I ordered one and used a cheap 10k in the meantime.

Set 11-01 from 5k to 16k - Carrier Frequency - I am currently set to 12k

Set 11-02 from 1 to 0 - 3ph modulation - Required for Sensorless vector mode

Set 00-12 from 60 to 120 - upper freq limit

Set 00-13 from 0 to 5.0 - lower freq limit

Set 00-14 from 10 to 5 - accell time in seconds

Set 00-15 from 10 to 5 - decell time in seconds

I did not change motor settings (voltage, current, freq, etc) changing them made things work oddly. Leaving them at factory worked fine. I think the VFD figures out what they should be via the current and voltage feedback loop, and that works better than telling the VFD what they are.

Note that I have a VFD rated 1000:1 motor (0 to 120hz)

Maybe include the following later on if motor heating becomes a problem. (no problems so far at)

Setup Cooling fan to run below 30 hz and Use the relay on RA & RB then:

Set 03-11 from 1 to 5 - on when output below
Set 03-12 from 0 to 30 - 30Hz switch point

 

[Mcgyver]

Since you guys are going deep into the VFD world…..

Agree with Susquatch The documentation, even developed world ones, are rough going. Still haven't figured out intermediate frequency, something to do with torque compensation. They also accommodate remote operation via PLC, so I figured there is a bunch stuff that I don't need to understand. The mean nasty sadists who write VFD manuals, are just a little less demonic than those who have entered The Guild of PID manual writers.

 

[deleted_user]

Hi Peter,

Do a search for "nema frame size" and you'll readily finds chart from which to match your dimensions. Here for example :https://www.grainger.com/know-how/equipment-information/kh-nema-frame-guide

I like your DP's counter shaft giving the low speed range. My Buffalo DP is one stage and the lowest speed is 580, I find it a bit hairy when using a tapping head so usually don't, which is sub-optimal. The flip side is speed changes are so easy, just grab the belt and move it.

I'm also thinking of converting mine to 3P and VFD. Slow speeds is imo where drill presses underwhelm but getting the slow speed is useless without power. Low speeds are needed for running a large drill or taping at a controllable speed is what my lacks (yours is kind of already there imo @ 215) so I plan on going with a 1725 motor. Going with a high rpm motor negatively impacts low speed power. Not sure I see the point of a high speed motor, if you think the rest of machine is up to it, you can always run the lower rpm motor over 60 Hz. Really though, are you going to need more than 3200 on that machine? if the answer is yes, imo you need something like a servo drill press. If the need for speed is really there, you're going to need high precision, balance, sensitivity. concentricity etc beyond what a larger DP offers. By starting with a lower speed motor, at tapping speed/large drill speed (say 2/3 - 1/2 reduction), there still should be enough power left.

As a VFD provides for low voltage controls, one I idea I have is to rig up a kill switch on a kick plate, basically a foot actuated e-stop. With one hand holding the work/vise and the other on the feed, a way to kill the power quickly if you feel something going wrong would be a good thing. In adding a VFD to a DP, it might be something to consider planning for in the wiring.

It all depends on the type of work Peter will be doing with his drill press.

I do model engineering and often drill teenie tiny holes at high rpm. I have limited speed options and seldom in the past have I drilled large holes.

Peter's belt drive options mean that he could go with higher rpm motor and still get plenty of low end oomph to use a hole saw to cut steel tubing IF he also wanted to have very high rpm on the high end.

That said, my drill press is an antique and perhaps the spindle couldn't handle as high an rpm as I'd want to use.

Which drives home the point, conversions depend on the equipment to be modified, and the type of work to be performed and one size does not fit all.

 

[Dabbler]

I should add that if you buy a TECO - (ahem, I am biased in the matter) The technical guys are superb - They got me started in 15 minutes flat! They'll help you get going if you get confused. (I was, at first)

 

[deleted_user]

I should add that if you buy a TECO - (ahem, I am biased in the matter) The technical guys are superb - They got me started in 15 minutes flat! They'll help you get going if you get confused. (I was, at first)

There is much to be said for good support if you need it.

Amazon VFDs = zero support which makes anything but the most basic install an adventure

 

[Former Member]

Here are some pics & specs. 215 to 3250 spindle rpm range based on belt/sheave combos. Jeez, maybe I should just get my butt in gear & shimmy up there more often. Belt move is a bit inconvenient but not difficult. Anyways looks like 1725 rpm, 1/3 HP moor. I don't see anything that defines the mount bolt pattern or shaft so I'll have to examine that more closely.

You understand you will have to replace the motor to a 3 phase for the vfd to work. For that drill press unless you have attachment to it not worth it.