[ESjaavik]

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?

[Swede]

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.

[Al_The_Man]

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.
Al

[HuFlungDung]

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

[Bloy2004]

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...

[Bloy2004]

Hu..
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.

[ESjaavik]

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.

[Swede]

: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.

Swede

[HuFlungDung]

Swede,

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.

[ESjaavik]

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.

[Swede]

Originally posted by HuFlungDung
Swede,

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.

[z28tt]

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 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.

Andris

[Al_The_Man]

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.
Al.

[z28tt]

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!

Andris

[Al_The_Man]

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.
Al.

[z28tt]

Al,
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?

Andris

[Al_The_Man]

That makes a more sense, yes you should always carry the ground through to any AC powered equipment.
Al.