View Full Version : VFD installation with pics

04-03-2004, 01:00 PM
After my wail for VFD help, and some excellent advice, I went out to PolySpede (www.driveswarehouse.com) here in Dallas to pick up a shiny new VFD for my vertical mill.

The current mill installation consists of a 4/8 pole (0.75/1.50 HP) 3p motor, 240V, fed with a "Phase-A-Matic" rotary phase converter. The rotary converter has served me well for many years, and being rotary, it produces a true, high-quality waveform. The 2 drawbacks are the noise it creates (even in the attic rafters; it's a nasty hum), and the mill itself, being step pulley, can be a bit irritating to change speeds.

Before I went out and bought this VFD, I did some experiments with a much smaller Hitachi VFD, a 4A job. Since the motor is 2-speed, I was able to attach the small 4amp VFD to the 4-pole motor inputs and proved to myself that the concept was sound and that the motor would respond well without overheating. It generated nice torque even at slow speeds. There was some PWM carrier noise which improved when I jacked the carrier freq. up to the max of 16 KHz. Upping the PWM carrier forces one to derate the VFD 20%, but the behavior of the VFD improves.

Here is the original 2-speed switch which I have dismounted.

04-03-2004, 01:01 PM
The motor cover removed... note the two sets of three phase inputs, one for 4-pole, the other for 8 pole rotation.

04-03-2004, 01:08 PM
The VFD I purchased is the Hitachi L100, capable of 10 Amps output at 240V. The input may be either single phase or 3 phase power. This gives me flexibility for the final installation. Many VFD's force another derating when used with single phase input, but not this one. The list of features is very long... modern VFD's are microprocessor controlled, and you can control acceleration, deceleration, braking, discrete speed levels, all sorts of cool functionality. It will output 360Hz, so it can be used with some HF 3phase motors, or the stock motor itself can be overdriven (go FASTER) with loss of some torque.

For now, I am going to mount the entire unit next to the mill head on an aluminum bracket. Ultimately, I can create a simple remote control keyset with a rheostat, or it can be controlled with a computer.

I went with the much larger 3HP VFD rather than a 1.5HP unit just to have the safety overhead on the current rating.

The display output can be set for current, frequency, or a user-defined scale which corresponds in a linear fashion with the frequency output. I'll probably set the latter up for a tach display.

Later today I'll power it up before going to the trouble of mounting it in detail, just to verify that it'll do what I want.

Stay tuned!:rainfro:

04-03-2004, 01:37 PM
I'm rivited to this one, Swede. Your demonstration is just what I(and many others, I surmise) were hoping for. Having followed that URL posted earlier regarding the L100's, your pictorial here makes the whole picture clearer. Especially your comments about the single-phase options. This seems to be an excellent and compact way of bringing 3phase power(variable) into a single phase environment, while reducing the discomfort of noise and mass.

04-03-2004, 02:04 PM
Thanks Bloy, I'll keep posting. I made a mistake already in the posts... the motor is in fact a 4/8 pole motor, but the more poles a motor has, the SLOWER the speed. So for this motor, when the output of the inverter is connected to the set of terminals which corresponds to 8 poles, the motor will be SLOWER. So more poles = SLOWER MOTOR SPEED. My plan initially is to connect it to the 4-pole set to get the higher speed, and set up the step pulleys to be one "notch" below top speed.

04-03-2004, 02:12 PM
hmmm. What is the purpose of the Slower 8pole hookup...is there more torque in this configuration? If so, it may be handy if switchable for those jobs requiring slow speed/high torque.
..just wondering...
John Bloy..(remember "the Waltons"?)

04-03-2004, 03:02 PM
I don't know the details of this particular VFD, but is the number of poles of the motor just a parameter to set up in the VFD? Then of course, the motor windings will be connected Delta or Star according to your real world choice.

True, the 8 pole setup will develop full horsepower at a lower rpm (perhaps 900rpm?). However, you don't want to "lie" to the inverter setup about the number of poles (by saying it is a 4 pole hookup when it is actually 8) , or it could allow too much current to flow and burn out the motor.

So it depends on what speed range you find really the most useful. It is conceivable to use the 8 pole setup and run the motor frequency up to 240hz to get 3600 rpm. This way, you will get full motor hp at 900 rpm, and it will stay at that hp up to the maximum. Whether this high of a frequency would damage your motor insulation is something to consider, perhaps.

The motor should not normally have a big imbalance problem up to 3600 rpm. If it does, I have had good success with disassembling the motor and balancing the rotor, just by setting up parallel knife edges, and letting the heavy side roll down. Just remove a little bit of metal from the aluminum bar fins of the rotor to improve the balance.

Be cautious of the quality of the fan if you run it up to 3600. Make sure the fan is in excellent condition, and keep it shrouded.

04-03-2004, 03:48 PM
VFD updates - The initial experiment is coming along nicely with one exception.

The first tests made use of a single phase 240 V input source. I randomly selected a "pole set", the right hand set of three terminals in the motor junction. After some initial programming to enable the pot and keypad, I had the motor spinning nicely at 60 Hz output, about 1800 RPM. The current draw was higher than I thought. This is a 10 Amp / 3HP VFD, and this motor is drawing 7.5 Amps. It's a good thing I bought a "bigger" VFD.

I set the accel and decel rates... it's nice to push a STOP button and have the spindle braked to a halt rather than having to apply a manual brake. 4.0 seconds is a nice accel, while 1.5 seconds for decel is perfect.

Thinking I was hooked to the slow set of motor junctions, I swapped the 'gator clips to the other... and found that the motor output was identical.

Hmmm. Maybe the function of the original switch was to route power to ALL SIX motor junction screws. I'll have to sit down with an ohmmeter and map that switch. It may be as simple as putting a shorting bar between the corresponding motor junctions to activate the high-speed.

The only bad part so far was that when I tried to feed the VFD input 3-phase power from my Phase-A-Matic, the VFD tripped (error), and the error code indicated "DC bus overvoltage". I'll need to do some research there. The VFD manual is almost 200 pages! There's plenty of protective logic built into the VFD, so short of a horribly incorrect wirng job, it looks like it will take care of itself.

Hu, thanks for the advise. I'm going to get a 115V AC fan and mount it on top of the motor. It'll run all the time to augment the internal motor fan, which will have little airflow at slow speeds.

I'll keep plugging and get some more data and pictures up. So far so good! The whole idea behind this VFD was to get rid of the rotary converter, and obtain variable speed to boot.:banana:


04-03-2004, 04:54 PM
Swede, If you have a true 2 speed motor, typically the lower speed will have approx half the current and half the HP rating. (The name plate should tell you). I would make sure you have the right 4 pole connections as that current appears to be a little high if that is off load, I would expect that current fully loaded at 60hz.
The switch usually connects the windings in either a series or parallel mode.
Also if you have the display set for rpm, and you are running at 60hz for a 4 pole motor it will show the speed/freq out i.e. 1800 but with a VFD with no feedback, this display is usually not the true speed but the frequency output, as a 4 pole motor cannot run at 1800 rpm (unless its a synchronous motor) due to natural slip action .
In some cases the overvoltage fault can be if you try to decelerate too fast, the regenerative action of the motor causes the bus voltage to climb above the recommended and the VFD will shut down.
There is usually an internal braking resistor to take care of some braking, for really fast braking, sometimes an external braking option is offered.

04-03-2004, 05:06 PM

There most likely is a parameter setting to reduce the hp rating of that VFD to match your motor 1.5 hp. Check that it is not defaulted to a 3hp motor rating, or it will allow a larger current than is safe for that motor.

04-03-2004, 05:09 PM
Good point Al,
I have seen $10,000 power supplys and drives blow up due to regenerative current not being handled correctly when it came back down the line. I would hate to see that happen here to the nice new VFD.

04-04-2004, 12:44 PM
Since you guys know a lot more about 3phase motors than I certainly do, let me describe exactly what is happening, and I'd appreciate any feedback.

The VFD continues to operate perectly with single phase input, except at an apparently reduced RPM. 3ph input still produces a bus overvoltage error. This doesn't bother me too much, as I ideally wanted to feed this VFD single phase anyway.

Here's the motor plate:

0.5 / 1.0 KW
780/3350 RPM

Remember from the picture above, there are 6 motor connection points, postulated as being 4/8 pole tie points. I mapped the original 4 position switch and how it distributes 3p to the windings. It is very simple. In FORWARD LOW speed, the right three posts are energized. In REVERSE LOW, the same three posts are energized, except 2 legs are swapped.

FORWARD HIGH and REVERSE HIGH does the same thing except to the left three posts.

The VFD manual specifies that it can handle 2,4,6,8 poles, but there is no input parameter to set the actual number.

When the three right posts are energized with the VFD (the LOW SPEED posts), the VFD is delivering 5.3A. When the left three posts are powered, the motor does not seem to be spinning faster, but the VFD is delivering 7.5 A. This is with the motor turning the spindle at its fastest pulley speed, a cutter installed, but no cutting taking place. No apparent excessive motor heating with either.

My plan right now is to set it up using the LOW speed posts. The spindle RPM is about 2200. I am going to increase the frequency of the VFD to bring the spindle up to 2500 or so, which is as fast as I've ever used it in many years.

I can program the VFD to limit current, as well as execute CONST TORQUE / CONST SPEED profiles. There are a lot of parameters to mess with.

Since the VFD has no ON/OFF switch, I am going to create a heavy relay box. The picture below shows the concept... a light toggle switch will energize the relays, one for each input line. These relays can handle 25A. Further, I have tied the DPDT contacts together to distribute the current within each relay. Energizing the VFD will also turn on a big 115V AC muffin fan which I will mount to the top of the motor to improve airflow.

All your suggestions are great! I am absorbing the information as I proceed. Really the only thing that is puzzling me is the reduction in top speed. The VFD is not limiting current at this point, as the most I have seen is 8A peak during acceleration.

Again thanks everyone.

04-04-2004, 01:26 PM
Swede... very interesting...
I had a twinge of nervousness when you didn't come back last night....a few years back while using a 220 welder to remodel our expanding city hall I had to tie into the main box...that went ok but when removing the welder's temp setup I inadvertantly created a short.....after the blast, and picking my butt off the floor I quickly threw the main switch back on while the administrator in the front offices (computer area)came out exclaiming.."what the hell is going on!" Fortunately no data loses occured, but a huge respect was gained for 220v high amps....any amps.
just a little request here....could you post also a picture with a broad view of your setup there?

04-04-2004, 01:44 PM

I am no motor expert, but the way I understand these two speed 3 phase motors, is that the switching between 4/8 poles requires certain rearrangement of the field coils from parallel to series, which in techno jargon is called a delta (series) hookup or a star hookup (parallel). The original switchgear would have this reconnection permanently wired for you. I am not qualified to advise you on how to do this if you have torn it all out :)

There should even be a chart of the connections perhaps hidden inside the lid of a terminal box on the motor, or perhaps in your user manual for the machine.

I think one common precaution is that you must never switch the main power connectors to the motor over while the VFD is operational.

04-04-2004, 02:10 PM
Thanks Hu, I'll do a bit more research. I am aware of the restriction re: switching off the input to the VFD with the motor turning, bad juju. There is some SERIOUS capacitance inside this VFD. After I pull the plug, it'll run its display AND a big heat sink cooling fan too for a good 30 seconds. Potential to get zapped big time.

Bloy, LOL I wasn't going to mention it, but I had a bit of an incident yesterday. The gator clips you see in the photos are fine for the output stage for the experiments, they get vaguely warm but nothing bad. But when I was playing with the gator clips + relays for the INPUT side, the current is much higher. It was scooting right along at 60 Hz when two input wires, which were laying across each other, melted together and made contact. There was a bang, about like a lady finger firecracker, and a flash of light.

When sh*t like that happens, the first thing you think is, "oh man I just blew up a $300 VFD". (flame2) Yanked the plug out of the wall, and sat there dumbfounded for a few seconds. Then I saw the melted mess that was the input gator clips. Of course the next minute is spent in anguish as you hook the thing back up properly and test it. No problems, the VFD didn't hiccup. The overcurrent was so short when
the lines contacted that the wire vaporized at the junction, and the circuit breaker didn't even trip.

Funny yes but POTENTIALLY LETHAL. STUPID!! (nuts) I had a 240V rat's nest. I MUST respect the voltages more and keep things under better control.

Right now the project is not fully together. The VFD was sitting on my mill table, and all the connections are temporary. Over the next couple of days, I'll do a final installation with proper wiring, and get some pics up. I'll also study a bit what everyone has to say so far in this thread, lots to chew on. If you are looking for a VFD, so far this one is very nice, but I noticed the Hitachi SJ100 series, for $80 more, appears more capable. I know you can program the number of motor poles into that one. The online manuals are full of valuable info. Also, the guys at driveswarehouse.com are great and very helpful.


04-04-2004, 02:20 PM
Hi Swede,

Important: take the time to read the manual.
Do NOT switch the leads from motor to VFD. I'm sure the manual explains this.

The motor will have constant torque (current limited) from almost zero speed up to rated speed. Then it will have constant HP (voltage limited) from there on. I have run motors up to 4 times nameplate, and nothing exploded, but it's *not* recommended, especially if motor is not enclosed well in case of a burst.

Do mount an auxillary fan if running at slow speed. You already found that out. If you exploit the full torque the motor will create just as much heat as at rated speed, but the built in fan will not do much.

Do put in the motor parameters before running the motor, or you may hurt it.

04-04-2004, 03:49 PM
Swede, The motor name plate indicates that you have a 2pole/8pole motor (unusual), the rpm of a 3ph induction motor on 60hz is 3600/number of pair of poles. (minus the amount of armature slip). So with the VFD set to a frequency out of 60hz should result in a rpm of either 780 or 3350, depending on setting.
Your HP on 780 is around .5hp on 3350 it is approx 1.3hp.
I would not run the VFD above 60hz if you are in the 3350 range, as the motor may not be designed to go over 3600.
The connections are usually kept in delta from high to low speed, and the poles are switched in as needed.
If I were you I would look out for a 4 pole 1.5 to 2hp with a single base speed of around 1740. It will give you a bit more flexibility.
P.S. On the 780 setting at 120hz will give you around 1560 rpm, I would not go above 120hz with a standard induction motor as the motor induction characteristics may cause problems and winding failure.

04-05-2004, 12:30 PM
Hi Einar, good to see you in this thread! How's the Kavo motor project coming? Do you have one of the "factory" kavo HF controllers?

Back to the VFD - I spent most of last night reading the VFD manual, digging out the bad Chinese translation of the mill's electrical system, and removing the motor from the mill. I need to slow this project down to do it right. I thought I'd be VFD'ing within a day or two, and I certainly could, but the installation would not be optimum.

Any time I do a project, there is an initial, high-speed "rush" phase, then comes a time when I step back and say "whoa, it's worth doing right". I'm learning a lot both from the advice here, and from my own research. I'm going to approach this from the power line all the way to the motor.

Step 1 - install a set of fuses. I'm going to set it up for three phase. If I want to do single phase, I can ignore the third line.

Step 2 - Lose the cheap relays and replace them with either a true contactor or a manual switch. Most guys here have an MSC catalog. There are a slew of contactors starting at page 3715, but my favorite is upper left on p. 3719, because it is MECHANICAL and simple, MSC#54032792. 30 Amps.

Step 3 - Somewhere on the output side of the contactor, I need to tap 115V for the motor fan. I'm going to try using a 240/120 transformer.

Step 4 - Install the VFD in a NICE, rigid bracket, with aluminum backing to absorb heat.

Step 5 - Install a new motor. This is a radical step, but here's why I am going to do it.

The motor plate does not agree with the mill manual. The manual shows a 4 and 8 pole motor, while as Al points out, the nameplate apparently shows a 2 and 8 pole. If the motor was, as the manual states, 4 and 8 pole, the RPM's would be roughly 900 and 1800, and that is what the motor is in truth. The top speed of the mill, as slightly over 3,000, comes from the step pulley arrangement. If the motor was 2-pole, then the motor speed + pulley should generate much > 4,000 RPM, and it doesn't do that.

I wanted to see what the motor face looked like, so I took the motor down and attempted to remove it from the base plate. In typical Chinese fashion, the pulley stack was secured in a fiendish manner; 2 BIG dog-point set screws. I removed one successfully. The other, being crappy soft steel, did not survive. the only wat to get the motor off of the base plate would be destructive.

Rather than jerk around with a motor of questionable quality, I am going to purchase a nice motor off eBay or perhaps MSC, one that's rated for inverter use, so I don't have to live with a setup that may crap out any given day from insulation and overheating issues.

Here's one on eBay that's tempting: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3806960203

Leeson makes a number of small motors which are rated "Inverter Duty" at reasonable prices. I'll need to machine a new face-mounted base plate for the motor, and install a new 3L pulley stack.

I am going to restore the mill to manual control for now, and methodically press on collecting the parts to do this right. I'll need the mill to machine a new motor mount plate from aluminum jig and fixture plate. I'll be glad to get the new motor mounted, as with a standard face mount, I can replace the motor with ease at a later date. Hmm with a 3HP VFD, I can do a HP upgrade, maybe 2 HP.

I'm going to print this thread, I want to thank everyone again for the help.

When I get the parts organized, I'll resurrect the thread if you guys are interested. And for anyone who is tempted to pursue this, let me say, from what I have seen so far, Yes go for it. To do a quick but solid installation with your existing motor and wiring is really a matter of a few hours work.

Here is a basic block diagram of the installation to come.

04-05-2004, 01:09 PM
I don't mean to hog bandwidth, but this PDF file from the Leeson website is too valuable not to pass on:


Great info on 3-phase motors. Leeson now makes pretty much ALL of their motors above 1HP "Inverter rated", meaning the insulation and construction is superior and able to withstand the rigors of inverter use. The prices are excellent compared to other manufacturers' inverter-rated motors, such as Baldor.

04-05-2004, 01:46 PM
Leeson: Can we trust a company that misspell their own URL? :-)

Your idea of more HP is very good. This way you will have more torque at low RPM, and thus not that much need for changing the belt to use big facing mills. Another feature with the motors you look at now, is that they use bearings with round balls in them, not cubes as the Chinese use.

And when you're messing around with the spaghetti in the electric department, why don't you implement an Estop? Just run the coil current for your contactor through a NC switch that release the holding current to your contactor when you hit it. You may also connect several of those in series placed on easy to reach places on your machine.

R--O O-----O-O---O-O--(Coil)-------S
_ |
R--O O--'

A= Solenoid holding contact.
B= Estop

When you press D the solenoid will close A, and you can release D.
If Estop is out, no coil current, solenoid opens.
If zero voltage, solenoid releases and must be manually restarted.
Oops! I see you use L1, L2,L3 where we use R, S, T. Just replace.

04-05-2004, 01:48 PM
That didn't come out well. If I just could figure out how to attach a sketch. You probably can make sense of it by inserting some spaces here and there?

04-05-2004, 03:08 PM
Thanks Einar. Contactors and motor starters in general are new to me and a bit confusing. MSC industrial (a big US mail order company) has a huge selection of them.

If I were to order a 3-pole 20 amp contactor, with a 240V coil, I assume that this would work for the feed into the VFD. How does a typical contactor "ON" switch work? Do you wire one or two momentary switches into contactor terminals? I am guessing that you hit the switch, which energizes the coils, closing the lines. Is there then another switch to de-energize? Finally, I'm guessing that the power fed into the VFD would not be considered an inductive load, because the VFD itself is what is handling the inductive load on its output side. These contactors vary from $40US up to hundreds of $$. Too much selection and a bit confusing. That is why I was leaning towards a mechanical switch.

I talked to both ENCO and Grizzly, who both offer my 8" x 36" mill, looking for the cast iron motor mount plate. Enco was worthless, but Grizzly did have it stocked, so hopefuly all I'll have to do is modify it for a 56C motor face.

I know I ramble a bit, sorry for all these long posts. One final question to anyone... in my shoes, would you go for a 3600 RPM motor or an 1800 RPM? I'm guessing the slower motor would be torquier at slower speeds, but to get the high speed out of the slow motor would require a pulley setup, or overdriving the VFD, both of which will reduce torque anyhow. I'm leaning towards the 1800 RPM motor and setting the spindle up for about a 3:5 pulley ratio for a top spindle speed of 3000 RPM.

04-05-2004, 03:08 PM
Swede, It looks like you have the right idea, for the 110 fan, look for a contactor that has normally open auxiliary contact/s. I agree with the idea for an e-stop, but for general pupose quick stops it might be better use a general stop button that takes advantage of the quick brake stop of the VFD, as interupting the supply in to the VFD usually causes a coasting stop. And its worth looking into a 3ph choke between the motor & VFD. Hammond electric used to sell them reasonabally cheap.

04-05-2004, 03:25 PM
Swede, the general principle of activating the main contactor, is that you add a latching circuit to keep the coil energized.
So for three phase, you would of course, have 3 power leads in and 3 out of the contactor. You also need an auxilary set of contacts, which will typically be a light duty set of points that mounts on the side of the main contactor. You would specify this when you order the main contactor as the aux contacts need to be made to fit onto the body of the contactor and to be mechanically operated whenever the main contactor closes or opens.

Typically, the holding coil should be run off of a lower voltage, like 24 volts, so that you don't have 240 volts running to your pushbutton stations. You can use an inexpensive transformer to get the juice for this circuit.

So the coil circuit is normally open, just like the main contactor. The "ON" button is a momentary contact, and provides a way to temporarily "jumper" the coil, which then pulls the contactor closed. When the main contactor closes, then so do the aux contacts, and you reroute the 24v through the aux contacts to provide holding power to the coil when you release the "ON" button. The "OFF" button simply breaks the holding circuit to the coil, and the springs in the main contactor push it open and all current flow is stopped.

If you can figure out how to wire this up on your own, you're a smart guy :)

04-05-2004, 03:27 PM
Hey Swede..keep on rambling(if that is what you call it)
your posts are informative or raise questions that are quickly answered by knowledgable individuals....
I'm learning a lot..although my absorbtion ports are a little restricted...

04-05-2004, 03:46 PM
Nicely said! I picked up a cheap monstrous industrial panel table saw that was 115v. But I wondered why it had a huge red/green buttoned on/off box full of contacts and latches, etc.
...then I realized that it had probably been a 230v 3ph setup prior to the retrofit. This one energized the coil with 115 volts.
..Thanks..now I understand the innards of that control switchbox....and why, if I didn't hold the green button in for that extra second, the machine wouldn't stay running.

04-05-2004, 04:20 PM
Now let's see if the schematics gets into the post.

I took a picture of one in my SysDrive manual that is pretty close to what I meant. The encircled X is the solenoid coil. The switches marked X are the solenoid switches. In addition to what I tried to draw ASCII, this one also routes the holding current through the fault relay inside the VFD so if it trips, the solenoid will release.

04-05-2004, 11:05 PM
:banana: That's great guys! That explains pretty much everything! There are some CHEAP contactors on eBay, I'll snap up one or two. Tomorrow, I will place an order with MSC for an 1800 RPM 2HP motor and pulley to replace the Chinese job. I think rather than make the contactor a complex affair, I'm going to do a 24V coil, 3 heavy lines, one aux. I'll simply energize the contactor coil ON/OFF with a toggle switch for normal use, and put an ESTOP switch in series. I like Al's suggestion to use the VFD stop as an estop for most occasions.

Half the fun of this project will be to create a cool remote for the VFD. Radio Shack sells a little membrane switch box which will be perfect. I'll add a pot for speed, and set up the keys for discrete RPM's, as the VFD allows one to program a series of pushbutton digital speeds to go along with the analog potentiometer.

Once again I am amazed at the depth of knowledge. thanks fellas, you've taken me from a kludge installation to one that I can use with confidence and pride.


04-05-2004, 11:24 PM

If you use a toggle switch, make sure it is only a momentary contact. You want the coil current to stay off if you have an emergency. Really, I would recommend that you buy a Stop/Start pushbutton station, because then it will be much handier to do the proper connections. :)

04-06-2004, 05:09 AM
And check the specs of your VFD and the membrane keyboard. These keyboards are only designed to drive a few milliamp, like the input of a microcontroller. Your VFD probably have an optocoupler at the input, and that could be more load than those buttons like over time.
Why not make a pendant with "real" pushbuttons? If the Estop button is like those I use, there is no need for an off button. Their action is very immediate, so I stop the machine by just a tap on the Estop. Then it will not lock in the off position and I don't need to release it by twisting or pulling. Then I use the separate stop buttons for spindle, motor, coolant and feed only when I want to stop only that function but the rest I want running.
In your case that means you connect all the other functions of your machine to the VFD L1/L2/L3 as shown above. Then you hook up separate switch to the off-input of the VFD, or you use a speed pot with integrated off switch.
One more thing: after you have hooked everything up but before you put on the lid, put your largest surface mill head in the spindle. Run up to max speed and command stop. If the VFD trips with overvoltage, lengthen the deceleration time. The more rotational mass you hang on the motor, the more energy it will have to stuff back into the capacitors.

04-06-2004, 12:25 PM
Originally posted by HuFlungDung

If you use a toggle switch, make sure it is only a momentary contact. You want the coil current to stay off if you have an emergency. Really, I would recommend that you buy a Stop/Start pushbutton station, because then it will be much handier to do the proper connections. :)

Excellent point Hu. I didn't think of that. If there is a severe input voltage sag, then the VFD may/may not trip, but the contactor would re-engage due to the toggle switch being ON, possibly causing unknown grief.

Einar, I'll take a look at the remote control info in the VFD manual. In the U.S., there is a company called DigiKey which is a boon for projects like this. They supply electronics components, and I'm sure that I can find some tactile switches which can handle plenty of mA, say 100 to 500, which should handle just about any digital signal requirements.

Today is motor day - I am going to order this motor from MSC - I could probably find one cheaper on eBay, but I want a new motor to go with the VFD.

http://www.leeson.com/findaproduct/index.html You must enter the motor number - 110451 - into the first text box. 2HP, 1725 RPM, C-face, TEFC.

10-17-2006, 02:27 PM
Bringing back this post from the dead... I've been curious about wiring the 2 speed motor to a VFD, since that's what my new (to me, actually a 1977ish) South Bend lathe has (2 hp 2 speed 3 phase reversible 230V). Was wiring the motor as simple as L1 and L2 in, and L1, L2, and L3 out to 3 of the six motor terminals? To change motor speeds, it's just turning the potentiometer knob? Looking at the Hitachi SJ200-015-NFU (http://www.hitachi.us/Apps/hitachicom/content.jsp?page=Inverters/ACVariableSpeedDrives/ProductDetails/SJ200%20Series.html&level=2&section=Inverters&parent=ACVariableSpeedDrives&nav=left&path=jsp/hitachi/forbus/powerequipmentsystems/&nId=iD) VFD manual, it can have two motor parameters, so I suppose it could be programmed to do either slow or fast speed, if the VFD is wired to the normal 4 prong plug.

Finally, whats the operation sequence? Flip the contactor/starter/breaker/relay to get juice to the VFD, have the lathe switch in one of the 4 positions, and press the start button on the VFD terminal? Or should it make more sense to remove the lathe switch, and directly wire to the motor, and not have the 2 speed option? This is all new to me, so I'm just trying to figure out what to do. There seem to be many options for VFD's, plenty of manufacturers, and I'm hoping to get lucky on Ebay... As far as specs, do I just need to make sure it has 1ph/230 input, 2hp rating, and 3ph output?

Would running a smaller VFD (1hp) be OK, but derate the motor to a 1hp torque/current level? I don't know if I'd need the full 2hp anyways, and I can always upgrade later. It seems the smaller .7kVa and larger 2.2 vfd's are more common than the 1.5 one I need for this motor. Would a larger one be OK, if I limited the max current with some parameters?

The VFD seems like a nice option to an RPC, especially since garage space is so tight... Thanks for the help.


10-17-2006, 02:51 PM
Your better off to go with a slightly larger unit, as you say you can usually limit current by parameter.
I would wire it up in the hi speed mode at first, if there is no limitiations, keep it this way.
If you hook up the 2 speed switch between VFD and motor, it should only be change over when the VFD is in Stop Mode.
I would wire up the contactor to come in whenever the e-stop released.
And then control start/stop and speed by the inputs.

12-06-2006, 10:34 AM
Follow up: I purchased the Hitachi SJ200-15-NFU, wired up the two 240V hots to the incoming terminals, the neutral to their neutral lug, the 3 motor wires to the output terminals, and a neutral to the lathe chassis ground. Since the SJ200 doesn't have a fwd/rev switch, I just used the barrel switch for that. The VFD has a PLC logic terminal that puts out 24V (I belive, it's been a few weeks since I did this), and I wired it to the 2nd phase on the barrel switch. When changing from Fwd to Rev on the switch, the output is swapped between 2 terminals. The terminal that's connected when the barrel switch is in FWD goes to the first logic input on the VFD, and the other terminal for REV goes the 2nd logic input. A completed circuit gets 24V on the logic input, and with a parameter change, these inputs are used for controlling motor direction. Easy! When the switch isn't on FWD or REV, the controller applies DC braking until the rpms drop below a low limit. I'd like a larger braking resistor (I think), since I get an over voltage error when the braking time is set too short (below 2.5 seconds). The LCD display is scaled by 29 to show motor rpms. I may set a 2nd scaler to correspond to spindle rpm, depending on which pulleys are being driven (SouthBend CL0145B lathe). After I tested it and got the motor turning, I set the parameters to limit max current draw based on the motor nameplate ratings, and bumped up the VFD frequency to 6 or 7 kHz to quiet down that high pitch electronic squeal/hum from the motor. I had a few wiring questions, and the engineer/tech guy my call was forwarded to at Hitachi was very prompt in returning the calls, and helpful. Great support there too. Thanks for your help guys - you made it easy!


12-06-2006, 05:42 PM
I am a bit puzzled why you hook the neutral up to the VFD and a Neutral to the Lathe chassis ground?
The way I read the manual, it is 3 ph or 1ph only, no neutral, and the neutral should never be grounded at anywhere but the service entry, the exception is if you have a local neutral set up and then it should only be at the power source.

12-06-2006, 05:58 PM
Thanks for bringing that up. I guess I mis-spoke in calling the ground a neutral?

I've got a 240V 50A 3 prong flat blade plug for the shop extension cord (originally to let me move the TIG around), which has the 2 hot legs, and the ground. The 2 hot legs are connected to the 1 and 3 terminals on the VFD, and the ground to the ground tab on the VFD. The ground on the receptacle goes to the dedicated ground bar on the sub panel in the shop (that the grounded 120V plugs use as well). This continues to the ground on the main panel. The 120V neutrals are not connected to this ground bus bar in the sub panel (in case anyone is wondering), they go to the neutral bus bar, and then to the main panel as well. In the main panel, both the ground and neutral bus bars are jumpered and connected to the service entrance ground, I believe.

When I received the lather, it had a 4 prong plug on the extension cord for the 3 phase motor. The 4th wire on the plug was screwed to the electrical box on the back of the lathe, to the chassis as a ground. I connected this to the VFD'd ground tab, same as the ground pole on the 3 prong plug. I figure the lathe should be grounded somehow, in case the motor windings short against the case, and put 120V on there. Is this kosher?


12-06-2006, 06:21 PM
That makes a more sense, yes you should always carry the ground through to any AC powered equipment.