# Variable Frequency Drives



## precisionworks (Mar 14, 2009)

This topic comes up quite a bit, and a short history may help users understand what they can & cannot do.

*What names are they called?*

VFD is pretty common today, but you'll also see reference to AFD (adjustable frequency drive), VSD (variable speed drive), AC drive, or inverter drive. 

*Are they something new?*

The first industrial VFD controls appeared in the 1970's, and they gained wide acceptance during the 1980's, due to advances in both power transistors (IGBT), and increased microprocessor capability. The earliest drives were able to control only speed, but not torque. Today's vector drive adds full torque control, which is critical to machine tool operation.

*Two basic types of VFD*

The earliest drives controlled voltage & frequency, and are called V/Hz drives. They are still available today, but are not useful for machine tool control. The reason is that when a V/Hz drive lowers the frequency (to lower the speed) it also lowers available torque. V/Hz drives are used to control fans & pumps, or any application where load decreases as speed decreases.

The newer VFD style is the sensorless vector drive that provides torque control. The microprocessor in the drive compares theoretical rotor position to actual rotor position, and uses an algorithm to increase voltage as torque demand increases. As late as five years ago, there was a big price gap between V/Hz drives & vector drives, but today the gap is nearly zero on smaller drives (3 hp and under).

*Buy new or used?

*This is one area where new is usually a better buy than used. EBay is full used drives, as well as new old stock, but documentation & factory support can be tough to get. A friend got a "great deal" on a newer GE-Fuji drive, only to realize that tech support calls go to Pakistan. Some of the better sources are Drives Warehouse, Factorymation, and Wolf Automation, plus many others. Make sure that what ever brand you buy comes with toll free tech support in your native language. 

*Enclosure types

*The basic VFD enclosure is called NEMA 1, which means it's open on all four sides for ventilation. These need to be mounted where metal dust & chips can't penetrate an opening & cause problems. You can mount a NEMA 1 drive in a closed metal box with an area 4X the size of the drive - the drive then radiates heat through the larger box, while keeping chips out.

The other common enclosure is NEMA 4X, which is totally enclosed, dust tight & water tight (suitable for outdoor use if needed). The advantage of this enclosure is that it's ready to plug and play without need for enclosure in a larger box.

*What if I only have single phase power?*

Most drives will take single phase power and convert it to three phase power. Even a drive rated for three phase input will work on single phase, but has to be derated 50%. Make sure your drive will accept single phase before purchase.

*Will a VFD eliminate changing gears or pulleys?*

It is a fine tuning device that does not eliminate the need for gear or pulley reduction. You can work with fewer gear or pulley changes, but it isn't a magic bullet.

*How slow can they drive the motor?

*Most motors work well down to 10% of rated speed, while still providing full torque. You have to remember that motors provide full hp at full speed, half hp at half speed, etc. If you plan to run slow under heavy load, install the largest motor & drive you can afford.

Another issue with extended slow speed operation is cooling. The fan on any motor is designed to cool the motor when it's running at full speed. If you plan extended runs at low speeds, you'll want to add a muffin fan that always runs at full speed.

*How fast will they drive the motor?

*You can drive the motor at 1.5X rated speed, with no noticeable loss of power. If the motor is driven at 2X rated speed, power drops in half. That still gives a range of motor speed from 10% to 150%, which works for most users.
*
Will lathe or mill controls still work?*

They will, but they will control the VFD instead of directly controlling the motor. The VFD is hard wired directly to the motor, with no switches in between. The machines switches are reconnected to the VFD control terminal strip, and tell the VFD to run/stop/reverse.

*Is a VFD hard to install?*

The first one can be intimidating. That's where factory tech support is really nice, as they help avoid the most common mistakes - like connecting 240v power to the wrong terminals (don't ask how I know, and yes, the drive was replaced under warranty). User manuals are mostly well written, some better than others. Setting the drive parameters (accel time, decel time, minimum freq, maximum freq, etc.) is not hard on most drives. IMO, taking out the single phase motor & bolting up the three phase motor can involve some time, and may involve fabricating a transition plate. Figure about a full day for the first one, including the motor swap. The following photos show my Burr King 482 with the 1 hp motor taken off, getting ready to install the new 3 hp motor.

*Transition plate welded & installed on Burr King base*







*3 hp, 3 phase Baldor bolted to transition plate*






*VFD mounted on the wall, away from the belt grinder. Gray box below the VFD is a disconnect (on-off control for the VFD).*






Feel free to ask any questions.


----------



## Anglepoise (Mar 14, 2009)

I don't want to hijack your thread but think this is in topic.

I have a heavy duty Hitachi 115 volt AC die grinder. I think the motor is referd to as a 'Universal type motor' as it is AC with brushes.

It spins at 25,000 rpm.

Now I have an inexpensive speed reducing box that allows me to dial down the rpm but this device I am sure is not very good for the die grinder especially at low speeds when it makes a ratcheting sound.

What can I buy that will allow speed reduction on this motor and at the same time allow long term use and reliability.


----------



## wquiles (Mar 14, 2009)

Thanks Barry for this post :twothumbs

OK, so I will start with the questions, since I want to do this conversion to my PM12x36 lathe:
1) Regarding the motor. I am constantly looking for that Baldor 3HP 3PH motor that you alluded to before in the forums, but I have also found a few that might or might not be "right" for the job. So what do I need (or don't)?:
a) 4 pole vs. 6 pole - would both work, or depend on the specific VFD drive?
b) Some are listed as 1750 RPM - are these the only ones to look for?
c) Sometimes I find the same motor, one designed for 50Hxz and other designed for 60Hz. Does it mater with the VFD?


2) Regarding the motor, part2. Based on the information you have, which of these would be good or not for such a conversion?
a) http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=220371961711

b) http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=180333710124

c) http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=180332057026

d) http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=220372519111

e) http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=270353432323

f) http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=270353447718


3) About the actual VFD's, something like these would work?
a) http://cgi.ebay.com/VARIABLE-FREQUENCY-DRIVE-INVERTER-VFD-NEW-3HP-2-2KW-10A_W0QQitemZ220364718355QQcmdZViewItemQQptZBI_Electrical_Equipment_Tools?hash=item220364718355&_trksid=p3286.c0.m14&_trkparms=72%3A1205|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50

b) http://cgi.ebay.com/Variable-Frequency-Drive-Inverter-VFD-NEW-3HP-2-2KW-10A_W0QQitemZ140303630544QQcmdZViewItemQQptZBI_Electrical_Equipment_Tools?hash=item140303630544&_trksid=p3286.c0.m14&_trkparms=72%3A1205|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50

c) http://cgi.ebay.com/3HP-VFD-Variable-Speed-Phase-Converter-1-to-3-Phase_W0QQitemZ250362302712QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item250362302712&_trksid=p3286.c0.m14&_trkparms=72%3A1205|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50

Thanks in advance,
Will


----------



## 65535 (Mar 14, 2009)

Anglepoise said:


> I don't want to hijack your thread but think this is in topic.
> 
> I have a heavy duty Hitachi 115 volt AC die grinder. I think the motor is referd to as a 'Universal type motor' as it is AC with brushes.
> 
> ...



Universal motors are normals AC/DC and run around 115 volts nominal, they are loud and inefficient, as with that they lose torque rapidly below nominal voltage and current. 

You're speed box is probably a variac type device, it will adjust voltage to the motor but you will lose marked amounts of power from the grinder. It shouldn't hurt the grinder you will not be able to dial down that motor very well. If you need variable power die grinding I would suggest an air powered grinder, but they still have poor torque at low speeds.


----------



## precisionworks (Mar 14, 2009)

> 4 pole vs. 6 pole - would both work, or depend on the specific VFD drive?


The number of poles determines motor rpm. The formula is:

RPM = 120 x frequency / poles

So a 4-pole motor has a synchronous speed of 1800 rpm, and a 6-pole motor has a synchronous speed of 1200 rpm. 

Most motors today are rated either either 1725 rpm or 3450 rpm, and all drives can be configured to will work with either motor. My preference is for 1725 rpm, as the fan makes less noise at full speed and the bearings last twice as long.



> Sometimes I find the same motor, one designed for 50 Hz and other designed for 60 Hz. Does it mater with the VFD?


The drive can be configured for either a 50 Hz motor or a 60 Hz motor, and both work equally well.



> which of these motors would be good


Some of those use a mounting system called a C-face. This is a common American mechanical standard designed with a large, thick flange on the face of the motor for mounting purposes. The weight of the motor is supported by the flange. Unless your machine already uses a C-face motor, you want to stay away from this design. 

Look for a motor like the one mounted on the Burr King (above), which is a common, rigid base design. The best type motor for machine tool use is called TEFC (totally enclosed fan cooled). The motor housing is sealed, so dirt & chips cannot get inside. The windings radiate heat through the shell, and the fan blows air over the shell to dissipate the heat.

The absolute "best" motor for VFD use is a style called TENV (totally enclosed non ventilated). These have no external cooling fan, and depend on a massive shell, sometimes finned, to radiate winding heat. They are as close to bullet proof as you can buy, but they aren't cheap (unless you get really lucky on eBay/Craigslist).

Some manufacturers brag about Inverter Spike Resistant magnet wire, claiming that it's something special. The fact is that all modern motors (high quality motors from both the USA and Europe) use 600v rated wire. The voltage spikes from a 240v VFD will never exceed 400v, leaving a wide safety margin. 

Look for a decent maker, like Baldor, Leeson, Westinghouse, WEG, Toshiba, etc. They rarely make a bad motor



> About the actual VFD's, something like these would work?


The first and second ones listed are both V/Hz drives, meant *only* for pumps & fans. The third one is a vector drive, and will work fine, but is high priced in today's market - and there may be no tech support.

My current favorite is the AC Tech, SMVector drive. In 3 hp with single phase input, Wolf Automation sells these for about $250 (NEMA 1 enclosure) or $340 (NEMA 4X enclosure). Other solid drives are the Hitachi SJ200, and the Teco-Westinghouse MA7200. Tech support is superb from all three manufacturers.


----------



## gadget_lover (Mar 14, 2009)

Thanks for the great write-up. It answers a lot of questions.


Daniel


----------



## wquiles (Mar 14, 2009)

precisionworks said:


> My current favorite is the AC Tech, SMVector drive. In 3 hp with single phase input, Wolf Automation sells these for about $250 (NEMA 1 enclosure) or $340 (NEMA 4X enclosure). Other solid drives are the Hitachi SJ200, and the Teco-Westinghouse MA7200. Tech support is superb from all three manufacturers.



Found them:
AC Tech:
http://www.wolfautomation.com/Product.aspx?ProductID=19500

Hitachi SJ200:
http://www.driveswarehouse.com/Drives/AC+Drives/Sensorless+Vector+VFD/SJ200-022NFU2.html

TECO MA700:
http://www.factorymation.com/s.nl/it.A/id.219/.f?category=41

All seem like they would do the job. It appears that the Hitachi and the TECO come already with the remote keypad (it is removable if I read it correctly) vs. being an accessory in the AC Tech unit. Plus the remote keypad in the Hitachi already has a built-in POT for the Speed control, which is nice, while the TECO comes built-in with the built-in dynamic breaking transistor 

Specifically for the lathe, how would you wire the control side of the VFD? Would you try to:
1) just re-wire the lathe's control panel re-using the buttons in the front of the lathe but with no remote keypad? or

2) re-wire AND use a remote keypad?

By the way, DRIVESWAREHOUSE is right here in Dallas where I live !!!

Will


----------



## jtr1962 (Mar 14, 2009)

Interesting discussion. Besides machine tools, variable frequency drives for three-phase motors have revolutionized the railroading industry over the last two decades. Here is a brief technical paper on an AC locomotive. Just as with tools, VFDs allow precise control of both torque and speed. As a result, wheels can be allowed controlled slippage which greatly increases available tractive effort (i.e. pulling power).


----------



## precisionworks (Mar 14, 2009)

> It appears that the Hitachi and the TECO come already with the remote keypad


Only the Teco MA7200 has a removeable keypad. It comes out pretty easily, and uses a telephone style cord & plug that goes into a jack on the drive. Both the SMVector & the SJ200 have a keypad built into the front of the drive.



> how would you wire the control side of the VFD?


You certainly want the lathe forward/stop/reverse switch to control the drive. That means running tiny gage wire from the lathe switch to the drive control strip (white & black wires below):







On the SMVector drive shown above, terminal #4 is a "common" terminal. Terminal #13A has to be electrically connected to #4 for the drive to start. Hitting the E-stop button breaks the circuit & kills output to the motor.

The other terminals all have assigned functions, and some of those are configurable. This allows the lathe or mill switch to control the drive, instead of using keypad control. You can also add a jog switch.

IMO, the remote keypad is not needed, unless the machine is located far away from the drive - so far that you cannot see the display. Most users wire the machines switches to the VFD terminal strip. If you want to add a remote speed pot, those are inexpensive & easy to do, or you can change speed with the keypad.


----------



## wquiles (Mar 17, 2009)

precisionworks said:


> IMO, the remote keypad is not needed, unless the machine is located far away from the drive - so far that you cannot see the display.


That is the thing - I was planning on installing the VFD on the back of the lathe, so the VFD would be completely out of the way, right underneath of the motor, like in this picture:






Or the VFD can be mounted/attached to the metal door that covers the lathe's electrical box.

I take it that you are assuming that the VFD is installed/mounted on top of the lathe? Is that the typical place to install the VFD on a lathe?

Will


----------



## wquiles (Mar 17, 2009)

precisionworks said:


> Some of those use a mounting system called a C-face. This is a common American mechanical standard designed with a large, thick flange on the face of the motor for mounting purposes. The weight of the motor is supported by the flange. Unless your machine already uses a C-face motor, you want to stay away from this design.



By the way Barry, I looked this morning, and sure enough, the factory 1ph motor "does" come with the rigid mounting design that you recommend - it is very beefy, and the motor besides having a fan in the back (looks like a TEFC design), has a heavy duty ribbed solid metal casting housing (you can see these features in the photo above). Not to bad for a cheap Chinese motor, right? 

The motor base is bolted to a base that swivels, to provide tension to the dual belts, so getting a new 3HP/5HP 3PH motor to bolt in there "should" not be too bad given the current setup.

Will


----------



## precisionworks (Mar 17, 2009)

> the VFD is installed/mounted on top of the lathe? Is that the typical place to install the VFD on a lathe?


Only your imagination limits the location ... I've seen them mounted on brackets near the headstock, on a wall near the machine, etc. As long as the cord from the VFD to the motor is 10 meters or less, you can mount it anywhere convenient.



> getting a new 3HP/5HP 3PH motor


3 hp and below is the least expensive way to go, as single phase input (240v) units are common. To run a 5 hp motor from single phase, using a VFD designed for three phase input, you have to double the size of the drive ... so it takes a 10 hp drive to power a 5 hp motor.

There are a very few 5 hp, single phase input drives, but they are spendy. Figure $600 in a NEMA 1 enclosure:

http://www.driveswarehouse.com/Drives/AC+Drives/Phase+Converter+VFD/PC1-50.html


----------



## wquiles (Apr 3, 2009)

Well, I now have a brand new Baldor 3HP, 3PH motor on the way to my house. All I need to do now is to actually buy a VFD to start the "conversion" process 

If I want dynamic breaking, any of the 3 VFD's above will/can do it, right?

Will


----------



## precisionworks (Apr 3, 2009)

> If I want dynamic breaking, any of the 3 VFD's above will/can do it


All three can be configured for dynamic braking, which will stop the spindle in a heartbeat. As long as your machine does NOT use a threaded spindle nose, you can use instant stop ... if you have a lathe that uses a threaded chuck mount, you risk dismounting the chuck & having it land on your toe:mecry:

IIRC, the Precision Matthews uses a camlock mount, so instant stop will work.

Take a look at the drives mentioned above, and look at the braking module or braking resistor prices, as you need both the drive & the module for instant stop. For the 3 hp SMVector drive, the module is $108.75:

http://www.wolfautomation.com/Configure2.aspx?ProductID=25569&x=58&y=26


----------



## wquiles (Aug 12, 2009)

As I work towards converting my mill to a VFD setup, this old thread is still very useful :thumbsup:


----------



## 65535 (Aug 13, 2009)

This should probably be stickied.

I was wondering for people with threaded chuck mounts if there was a way to maybe add a bolt or set screws so that with dynamic braking it wouldn't dismount the chuck?


----------



## precisionworks (Aug 14, 2009)

> a way to maybe add a bolt or set screws so that with dynamic braking it wouldn't dismount the chuck?


I've never seen any type of secondary lock for a thread mount spindle. Unless you can come up with something that's 100% reliable, the best bet is to let the motor/spindle coast to stop. Next best is a gentle decel, maybe four seconds or so.

Most drives, unless a braking resistor is installed, will fault out on regenerated voltage when the decel time is under roughly five seconds. The only way to find out is to lower the decel time & try it, lower it by another second & try it, etc. With the resistor, you can decel as quickly as the machine plus belts (or gears) will tolerate.


----------



## wquiles (Aug 14, 2009)

precisionworks said:


> I've never seen any type of secondary lock for a thread mount spindle. Unless you can come up with something that's 100% reliable, the best bet is to let the motor/spindle coast to stop. Next best is a gentle decel, maybe four seconds or so.
> 
> Most drives, unless a braking resistor is installed, will fault out on regenerated voltage when the decel time is under roughly five seconds. The only way to find out is to lower the decel time & try it, lower it by another second & try it, etc. With the resistor, you can decel as quickly as the machine plus belts (or gears) will tolerate.



Question (since I am about to order the VFD controller for the knee mill) = How do I know if I need the external braking resistor or not for my knee mill?

Second question: Where can I find NEMA4 push button / E-switch enclosures? What about a NEMA4 enclosure for a speed pot?

Will


----------



## precisionworks (Aug 14, 2009)

> How do I know if I need the external braking resistor or not for my knee mill?


If you need to stop the motor faster than four or five seconds, the brake resistor is needed. You can set the drive lower, but it will fault on over voltage. To make the motor stop instantly, the resistor is needed.



> Where can I find NEMA4 push button / E-switch enclosures?


Factorymation carries them, about $30 each:

http://www.factorymation.com/s.nl/it.A/id.3898/.f

But for $3, you can buy a metal switch box at the hardware store, add a cover with 7/8" hole (which fits the 22.5 mm standard) and you're ready to go. I don't worry about NEMA 4X for e-stops or speed pots, as those cost about $5 to replace. I do think it's worth the money to buy a NEMA 4X drive as those cost $300 to replace.


----------



## wquiles (Aug 18, 2009)

Gotcha - I will skip the resistor for now. For the box, I might use something simpler, but will likely get a sealed pot, which are not that expensive ($10-15).

Thanks,
Will


----------



## gadget_lover (Aug 18, 2009)

On the way home tonight the traffic was heavy. I ended up thinking about a VFD for my mill too. It would be a nice upgrade, a good use for my birthday money.

I'll be watching this closely. 

Daniel


----------



## precisionworks (Aug 19, 2009)

A few things to keep in mind as you plan a VFD conversion ...

How slow you plan to run the motor is largely dependent on the hp of the motor. Say that your mill has a 2 hp motor & does just fine (at full motor rpm). If you stay with 2 hp & plan to run the motor at 1/2 speed, you will have 50% of motor hp available ... at 1/4 motor speed, there is only 25%, etc. If you plan to run slower than normal, start with a motor that's bigger than the one on the machine.

For motors up to 3 hp, with 240v single phase input, expect the VFD to cost about $100/hp. For motors larger than that, the cost jumps to $150/hp. If 3 hp is large enough, considering the lowest motor speed you plan to run, it is the biggest motor that still uses a lower cost VFD.

For budgeting, add up the following:

VFD cost +

Motor 

Braking resistor 

Power cord 

E-stop switches

Switch enclosures

Speed pot & enclosure

Mounting bracket if you buy a commercial version

New sheave for larger diameter motor shaft

Some of those items are low cost, others may surprise you. The sheave for my mill conversion cost $83, including shipping & tax - just a bit more than the $29 for a "normal" sheave.


----------



## wquiles (Aug 19, 2009)

precisionworks said:


> A few things to keep in mind as you plan a VFD conversion ...
> 
> How slow you plan to run the motor is largely dependent on the hp of the motor. Say that your mill has a 2 hp motor & does just fine (at full motor rpm). If you stay with 2 hp & plan to run the motor at 1/2 speed, you will have 50% of motor hp available ... at 1/4 motor speed, there is only 25%, etc. If you plan to run slower than normal, start with a motor that's bigger than the one on the machine.
> 
> ...



Thanks much for the check list Barry 

- Motor: already got home a new Baldor 3HP, 3PH motor
- ACTech, SMVector, NEMA 4X enclosure, 3hp with 240v single phase input VFD: Just bought it 5 minutes ago - probably get it next week.
- E-switches with enclosure: Bought earlier today from McMaster-Carr
- Pot and dial for pot: Bought earlier today from McMaster-Carr

There is no turning back now :naughty:


----------



## precisionworks (Aug 19, 2009)

> There is no turning back now


I know the feeling. My 3 hp Baldor, the one that weighs 93#, has been sitting on the shelf for quite a few months. The identical VFD came a couple of weeks ago, and the step sheave delivered last week. I started to tear down the mill on Friday last, but a friend stopped by and had me fab a Warn winch solenoid mount for his new Jeep ... finished that at 10:00 Saturday morning (6 hours total labor). He then helped me install the Blu-Ray player and home theatre system, which was finished by supper time on Sunday (another 6 hours, mostly his labor). Which meant that nothing got done Friday, Saturday or Sunday. Now it's time to catch up


----------



## StrikerDown (Aug 19, 2009)

precisionworks said:


> ... home theatre system. Which meant that nothing got done Friday, Saturday or Sunday. Now it's time to catch up



 New home theater system... 
Catch up may be longer than you think!


----------



## wquiles (Aug 20, 2009)

For mounting a VFD drive in a swing-out arm (so that it can be moved out of the way or adjusted as needed), what do you guys think about using something like this TV mount? I can attach the base to the knee, and for about $30 bucks have an adjustable and sturdy mount.

This one can hold up to 33 pounds (the VFD is much lighter):
http://www.buy.com/prod/videosecu-wall-mount-bracket-for-small-size-lcd-led-monitor-flat-panel/q/loc/111/211485560.html


This one is rated to 60 pounds (still an overkill):
http://www.buy.com/prod/level-mount-dc30dj-full-motion-mount-for-10-to-30-lcd-and-plasma-tvs/q/loc/101/208226751.html


What do you guys think?


----------



## precisionworks (Aug 20, 2009)

Great idea about using the TV mounts :thumbsup:

I use nothing but Level Mount for all custom flat screen installs. Their products are very nicely finished, and well engineered. In fact, the larger version of the one you are looking at is supporting my 37" HDTV.

The largest Level Mount I've used is their DC65MC - $350 for the mount plus another $250 for a custom made square tube, cross wall support for the mount. Even though the TV weighs 88#, the Level Mount is rock solid. I don't trust anything else.

http://www.levelmount.com/p-91-leve...ilt-extend-14-fits-34-to-65-tvs-and-200-.aspx


----------



## wquiles (Aug 20, 2009)

precisionworks said:


> Great idea about using the TV mounts :thumbsup:
> 
> I use nothing but Level Mount for all custom flat screen installs. Their products are very nicely finished, and well engineered. In fact, the larger version of the one you are looking at is supporting my 37" HDTV.
> 
> ...



Cool - I went ahead and ordered the Level Mount one 

This morning I got confirmation that the VFD is being shipped today!

Getting closer to having all the pieces/parts :devil:


----------



## jasonbarber (Oct 7, 2009)

There are lots of different articles at the following link ralated to VFD drives & it's applications.

Eg. What's an ac drive? , How does a vfd work? , How to maintain a vfd?

http://www.ctiautomation.net/Articles.htm


----------



## wquiles (Apr 20, 2012)

Bumping this old thread with an excellent article on VFD's:
Teardown: The nuances of variable-frequency drives

Will


----------



## 350xfire (Apr 25, 2012)

wquiles said:


> Cool - I went ahead and ordered the Level Mount one
> 
> This morning I got confirmation that the VFD is being shipped today!
> 
> Getting closer to having all the pieces/parts :devil:



You should be ashamed of yourself!!! You should have spent days fabricating one instead you went out and boutght one for $18! Shame on you!!!


----------



## wquiles (Apr 25, 2012)

350xfire said:


> You should be ashamed of yourself!!! You should have spent days fabricating one instead you went out and boutght one for $18! Shame on you!!!


I know, I know ... (goes back to the cave and hides in shame) ...


----------



## gt40 (Apr 26, 2012)

This thread has got me thinking about converting my b24 agazzani band saw. It is a big metric motor though- around 5 hp...


----------



## 350xfire (Apr 26, 2012)

gt40 said:


> This thread has got me thinking about converting my b24 agazzani band saw. It is a big metric motor though- around 5 hp...



5hp BFD = $$$ unless you find a good Ebay one.


----------



## gt40 (May 16, 2012)

I just bought this 3hp motor for my mill or lathe after speaking to the owner. It is supposedly new condition old surplus:







I am torn between the wj200 hitachi vs the teco ma 700 mentioned. The new Hitachi replaces the sj200 and has braking built in and is a bit more. The older one is listed as obsolete. The AC tech listed in this thread is more when you add the resistor and the teco is similar in price. Considering the recommendations were made in 2009, I wanted to see if there is anything better today. Any new updated drives I should consider?


----------



## precisionworks (May 18, 2012)

gt40 said:


> I am torn between the wj200 hitachi vs the teco ma 700 mentioned. The new Hitachi replaces the sj200 and *has braking built in* and is a bit more. The older one is listed as obsolete. The AC tech listed in this thread is more when you add the resistor and the teco is similar in price. Considering the recommendations were made in 2009, I wanted to see if there is anything better today. Any new updated drives I should consider?



Almost every drive has braking built in ... as long as there's nothing to brake except the rotor of the motor itself. The EMF generated by the coasting motor is dumped into a braking transistor & it does slow the rotor more quickly than a coast-to-stop. Not terribly useful on a lathe or mill where there's lots of inertial mass that you want to stop FAST. The WJ200 manual says that without resistor the braking is limited to 50% @ ≤ 60Hz. In real world terms this means one second of braking followed by one second of coasting followed by another second of braking, etc. With resistor braking is 150% @ all frequencies. 

The WJ200 does have the dynamic braking module built into the drive so you don't need to buy that as an extra part. You will need to buy enough resistors to stop the load. Page 41 of the manual says this:



> If you need the motor and load to decelerate quicker than their natural deceleration during coasting, we
> recommend installing a braking resistor.



http://www.clrwtr.com/PDF/Hitachi/Hitachi-WJ200-User-Manual.pdf


----------



## gt40 (May 18, 2012)

Thanks for the info. so you still recommend the AC Tech as your current favorite?


----------



## cmacclel (May 18, 2012)

Funny I just bought a 2hp Lincoln Surplus 3-Phase 1725 RPM to retrofit my RF-31 Mill. I'm going with the KBAC-27 Controller. I have a KBAC on the 2 x 72 Grinder I just built and love it.

Mac


----------



## StrikerDown (May 18, 2012)

WOW Chris... Awesome grinder!


----------



## cmacclel (May 18, 2012)

StrikerDown said:


> WOW Chris... Awesome grinder!



After seeing this video I had to have one! Watch how fast it removes *Hardened* Steel! Grinding starts at around 1:25 in

http://www.youtube.com/watch?v=kvlKfzW12d0


----------



## gt40 (May 18, 2012)

Is that a KMG grinder? Looks kinda like it. Good looking design in any case...


----------



## cmacclel (May 18, 2012)

gt40 said:


> Is that a KMG grinder? Looks kinda like it. Good looking design in any case...



Its a Grinder in a Box which is similar to the KMG.

Mac


----------



## StrikerDown (May 18, 2012)

Chris,

 When you do the upgrade to your RF-31 can you snap a few pics along the way, I am sure I'm not the only one that would be VERY interested! :naughty:

Please please please!:bow:


----------



## cmacclel (May 18, 2012)

StrikerDown said:


> Chris,
> 
> When you do the upgrade to your RF-31 can you snap a few pics along the way, I am sure I'm not the only one that would be VERY interested! :naughty:
> 
> Please please please!:bow:




Will do......the KBAC-27 shipped out a few days ago and according to UPS should be here Tuesday. My RF-31 Forward / Stop / Reverse switch is getting flakey so now was the time. I can't wait for now belt changes 

Mac


----------



## wquiles (May 18, 2012)

Very nice build there for your grinder Mac!




cmacclel said:


> After seeing this video I had to have one! Watch how fast it removes *Hardened* Steel! Grinding starts at around 1:25 in
> 
> http://www.youtube.com/watch?v=kvlKfzW12d0



Nice video. Having enough horsepower available does help a lot 

I am also building my own, and I will be using a 3HP motor with the same AC Tech NEMA4 VFD I used in the Quincy and knee-mill conversion. I bought a welded frame from Ebay, I got the motor, but waiting to buy the VFD now :devil:

Will


----------



## StrikerDown (May 19, 2012)

cmacclel said:


> Will do......the KBAC-27 shipped out a few days ago and according to UPS should be here Tuesday. My RF-31 Forward / Stop / Reverse switch is getting flakey so now was the time. I can't wait for now belt changes
> 
> Mac



Know belt changes would be great... I'm looking for a project! :naughty:

Right after I figure out how to run the TIG!


----------



## precisionworks (Jan 10, 2014)

Found this white paper while looking for VFD info. Eight pages in total with the first 4.5 pages as an excellent explanation of the VFD as part of a control system. 

The last 3.5 pages are advertising for the company that wrote the paper (Lapp USA). Nice cable for about $5/linear foot.

http://www.idspackaging.com/common/paper/Paper_286/VFD-White Paper.pdf


----------

