When I found an absolute STEAL on a milling machine, I bought it..... BUT, the mill has a 1-1/2 HP 3 phase motor on it. Initially I had planned to purchase a NEW single phase motor to replace it.
That was until some of the discussions on the internet explained what a Variable Frequency Drive, VFD, or Motor Drive was. A few searches showed that I can purchase a VFD with MORE capacity that I needed, for only SLIGHTLY more than the replacement motor would have cost me.. COOL..
AND, the VFD would provide: Soft Start of the motor/mill, electronic Variable speed, Electronic OVER speed of the motor, Nearly instant braking of the motor and mill, and 3 - phase power for OTHER devices in my workshop.
The one thing that complicates the setup of 3 phase equipment with a VFD's is that VFD's are NOT well understood by home hobbyist, and the manuals provided are well...... translated from Chinese if that says enough.
In this blog post I want to document my experience in setting up a VFD. Which is actually VERY easy to do. Once you get past the lousy documentation..
I settled on the Teco FM-50 model 202 which is 220 volt single phase input and 220 volt 3 phase output VFD. It is rated to drive up to a 2 HP motor or, more accurately capable of up to 7 amps of output.. I am planning to drive a 1-1/2 HP 3 – Phase motor on my RF-30 Mill Drill with this unit initially.
The AC hookup was very straight forward. Points to note are that the 3 phase output of the VFD MUST be wired directly to the motor (no switches or fuses in the lines).
My AC input for this is a 20 amp 220 volt circuit that I use for my Lathe and Mig Welder (I have a 220 - 20 amp plug on the wall in my shop.). There is NO Neutral in that connection, so the wiring on the VFD INPUT side goes to L1, L2 and then of course the Ground Tab.
The cord I located to run from the VFD OUTPUT to the RF30 mill's motor only has 3 wires in it, so I ran a separate 14 gauge ground wire to the motor. I also ran that same ground wire to the Mill itself to ensure it was grounded as well.. I attached the wire to the head so that everything is grounded.
My 3-phase motor ran 'backwards' (as is often the case) when I first setup the wiring. But changing directions on a 3 phase motor is as simple as swapping 2 of the 3-phase wires at the motor, which corrects that problem. I powered everything off, and swapped the first and second wires around at the motor to correct the direction of rotation problem
One thing to note is that, when I unplug the VFD, its takes almost 30 second for the display to go off. So I am careful to wait until it is TOTALLY off – dead – (blank display) before I touch the power wiring.
If you don't want or need a "remote control" panel for the VFD and are OK using the start - stop buttons on the front of the unit, that's about all you need to do for the setup. There are some programming or settings changes you might want to make even without “remote controls” to tailor the VFD's operations to your liking. But I started working with and running the VFD and mill with ONLY the power connections and controlling the start/stop and speed of the motor right from the VFD front panel.
To ensure that everything was setup from the factory correctly one of the first things I did programming wise to the VFD, was to force a "factory reset" by setting function 25 to 020 (for 60 Hertz power). Many comments on the net indicated that people sometimes had weird symptoms or operation issues with the VFD until they reset it to factory defaults. I figured it would be best to just start there.
Setting up remote controls for forward – reverse and variable speed can be done with a single switch and a single Potentiometer (often referred to as a 'Pot'). I got my parts from Radio Shack. A Single Pole – Double Throw – Center off switch (SPDT), part number 275-711 was $3.50, I think it was described as a replacement automotive switch. There's no need for heavy duty or anything like that. The switch was cheap and the longer handle – paddle on it seemed to me like it would work well in the shop. I also picked up a part number 271-1715 10k Ohm Linear taper Pot (also $3.50).
There are two possible 'tapers' in Pots. One is called audio taper and the other is Linear. As the name linear implies this type of pot has a straight line increase in resistance as you turn the knob. An audio taper is more like an exponential curve and the increase in resistance is NOT a straight line. IMO the straight line change in speed is what we want for machine operations.
All of this, the switch and Pot, can be housed in a wall outlet type junction box and it only needs 6 low voltage wires to connect it. For my junction box I choose an old metal one I had lying around because I could stick a magnet on it and then just 'stick' the “control panel” to the mill's head. I used a blank metal cover plate that I drilled out to accept the switch and Pot's shanks. (and you could just as easily use some heavy sheet metal for the cover or the entire box for that matter if you have a bending brake. A plastic cover might not hold up well with the toggle switch snapping back and forth in it..)
I had a nice length of hookup wire (which actually has about 12 wires in it instead of 6) that I used to make the hook up. You can use telephone wire, 'intercom' wire or network cabling. Anything that could be used for low voltage connections. Stranded wire would be more flexible, but the cable I dug up for example is solid wire.
One word of warning on Network cable, it generally has 8 wires in it.. BUT those are configured as “4 pairs” and the color standard in the cable, is Blue – White, Green – White, Orange – White and Brown – White. Depending on the cable vendor or supplier, those 4 white wires may NOT be color coded. They may only be twisted or wrapped with their “paired” wire, the Blue, Green, Orange, or Brown. You might find that you can not tell which of the 4 'white' wires is which in that type of cable. Before you decide to buy or use networking cable it would be advantageous if you can check the end of the cable, or cut into the jacket so you can see how the wires are color coded.
The ideal version of Network cable to use has each of the white wires marked with a colored stripe. One white wire would have a blue stripe, one has green, orange, etc. That way you can keep the wires straight as you're wiring things up. For a basic setup you only need 6 wires, and a network cable usually has 8. Whether the wire is “twisted pair” type wire or not should not matter in this case.
One of the things for me that made this setup VERY confusing were the MANUALS. The versions of the Teco FM-50 VFD manual I downloaded off the net were OLD and do not include some of the diagrams and details that the pocket sized manual that came in the box has. The first additional page or diagram in the pocket manual that I though was useful is a block diagram of the power wiring:
Apparently the reason for that is because the VFD electronics are constantly monitoring the motor and IF the motor is disconnected the VFD will continue to attempt to drive the motor, even though its disconnected and that can FRY the VFD..
In my case I do plan to eventually share the VFD between the Mill and the Metal lathe. BUT, there will be a AC disconnect installed BEFORE the VFD so I can power it completely off. Right now it has a line cord to a 220 – 20 amp wall plug that I use to power it off..
I plan to eventually be able to switch the motor connections with a pair of L14-20 twist lock plugs on the VFD output. To do that it will be necessary to power the VFD COMPLETELY off, unplug one motor, plug in the other motor and then power the VFD back on. That's part of why my “Control panel” is 'mobile'.
I was really confused by the descriptions of the 'multi-function' inputs in the manuals. I could see the multi-function outputs described in the pin out diagram. BUT, the way the diagrams look to me, all of the Input lines are labeled as having a single function.. The diagrams as presented lead me to believe that Pin 6 is SP1 and Pin 7 is Reset, Correct? Well actually NO. Pins 6 and 7 can each be assigned anyone of 6 DIFFERENT functions. Pins 6 & 7 ARE the multifunction INPUTS...
Also pins 3 and 4 can either be setup as: ON/Off for Forward and ON/Off for Reverse OR Pin 4 equals Direction and Pin 3 is Start/Stop. For our use and simplicity in setting this up, the 1st option, 3 = Fwd and 4 = Rev is the simplest setup.
Another page that is missing from the Online and OLDER manuals is the options, or programming chart. This charts lists ALL of the options for all of the 'functions' in ONE PLACE. Notice the 4th column for Functions 19 & 20 as an example.
The chart also makes it clear that the multi-function OUTPUT can be set to 3 different outputs. The multi-function OUTPUT (pin 1 and 2) can be; On when the VFD has power, or ON when the motor is up to Speed, or ON when the VFD has a fault.
Let's get back to the wiring and setup for a plain and simple forward – reverse with variable speed type remote control.
Our SPDT (center OFF) switch needs to have the 12v common (pin 5) connected to the center tab on the switch. Fwd (pin 3) should be connected to one of the outside tabs, Rev (pin 4) needs to be connected to the other tab. The Radio Shack switch has tabs on it that are actually sized so they can take push on – 'FastOn' type crimp-on connections. If you want to skip the soldering, at least on the switch, you could use crimp type connections here.. Unfortunately the Pot is a solder only type of connection.
When you are setting this up and labeling the switch keep in mind that inside, the switch is connecting that center wire to either one and only one of the FWD, or REV wires. AND, the pin or wire it is connecting to is the OPPOSITE of the direction the handle or paddle is pointing. There is pivot inside the switch and if the paddle is UP, then the switch is connecting the center and BOTTOM wires together.
If you apply the 12V line to FWD (pin 3) the VFD spins up the motor in the FWD direction.. When you remove the 12v signal from the pin (3 or 4 in this setup) the VFD goes into STOP or spin down mode based on the setting of function 14 “Stop Method” (the default is a controlled 5 second spin down).
In my case, if I connect 12v to pin 3 the mill runs forward, remove it and the mill stops. Connect 12v to pin 4, the mill runs reverse, remove it and it stops. That's why the switch MUST be a 'center off' switch for this type of configuration.
Variable speed is just about as simple. As the pin out diagram shows, one end of the Pot is connected to pin 8, the other END to pin 10 and the center terminal on the Pot to pin 9. The wiring diagrams for the nema enclosure versions of the VFD actually shows this kind of setup in the manuals (without the pin numbers shown!) I added them to this diagram:
With the 'hardware" all setup, what 'software' - Program settings do we need to make our remote control setup work? After the reset (function 25 set to 020 for 60 Hertz type power.) we need to set:
F 6 = Frequency UPPER limit. The Default is 60 Hz, I like to run the mill up a little higher, so I set it to 90 Hz.(And yes that means I am OVER driving the motor.. But now instead of having to loosen and swap belts, I can just dial up the speed I want... )
F 7 = Frequency Lower limit. Default is ZERO?? I set it to 15 HZ and this will be the LOWEST speed I can dial with the remote control POT. Turning the pot to the limit of its travel will not go any lower than this setting.
F 10 = Start/Stop control Default is for the KEYpad to control start/stop, we want the remote, set this to 1 (terminal TM2). Which is NOT to describe a pin number, but the Terminal BLOCK. Apparently the AC terminal block is TM1 the smaller control lead block is TM2. Because we LEFT F 3 (operation Mode) at the default setting of 0, pin 3 = Fwd/Stop and pin 4 = Rev/Stop which will cause the remote to function as we expect it to.
F 11 = Frequency Control Default is for the KEYpad (again) to control Frequency. We want remote so we set this to a 1, (terminal).
That's all the program settings we HAVE to change to make this work. You can of course play with the Accel and Decel (braking time). You can play with Stop method settings, etc.
If you want you can use more wires and with more switches you can add; Jog, Emergency stop, etc. Any of those 6 options listed for functions 19 and 20.
I did actually add a spring loaded momentary switch to my configuration (seen on the extreme right of the first photo) because I wanted to add an emergency stop.
What I discovered is that the Emergency stop, does the SAME THING as a regular stop if you have controlled Decel mode enabled, F 14 = 0 and the decel time, F 2 set to something low like 1.5 seconds.
You may also need to increase the DC braking time to get the VFD to completely stop the motor. But that might also cause an overload if the motor is running at high speed, at 90 Hz for example. Then you'll probably need to add a braking resistor. Check on eBay.. I got a 150 Watt, 100 Ohm resistor from China for less than $20,,
Based on what I observed I really don't see any difference between Emergency stop and a normal stop. It seems to follow the Stop Method (F 14) setting and the Decel time. If I set the Stop Method to coast, then the emergency stop just lets the mill roll to a stop. I'm either missing something as far as the setup goes or Emergency stop is a bit of smoke and mirrors.
Some functions of the FM50 seem a little ODD to me. For example I wired up my momentary switch to pin 6 and set the option to 1 – jog. When I enable the signal nothing happens. The display on the FM50 shows the JOG frequency (F 9) I have set, but the motor does not turn. It seems you have to do a JOG, plus FWD or REV to get that to work. Since the FWD and REV lines “start” when you enable them I ASSUMED that the JOG, SP1, and SP2*4 commands or options would do that same. But apparently NOT. (it looks like you have to enable JOG, then also enable FWD or REV to get the motor to run.)
What I DO like about the VFD is the variable speed. I set my Frequency lower Limit (F 7) to 15 Hz, which is 1/4 of the normal frequency and normal speed. The VFD lets you change the “speed” even when the motor is not running. (Which kind of negated my need for 'jog'...)
My normal mode of operations now are that I do my setups on the mill, I dial the speed all the way down, which only goes down to 15 Hz, and I start the mill motor. At that slow speed I can check for cutter touchdown.. I can also make sure things are clear. Like the one time I had the face mill over too far and at 15 Hz, the motor just turned until the cutter hit and stopped. I immediately switched off and corrected my mistake, but it's a nice check before I really start cutting.
Once I decide my slow speed check is OK, I dial the VFD, with the POT in the “remote control” up to the speed I want to run and start cutting. I mounted my FM 50 up on the wall actually over my lathe, in part because I plan to share it. But I also wanted to make absolutely sure that no swarf or coolants, got inside the VFD. This size unit does have a cooling fan that COULD suck stuff into the unit, and the manuals are rife with warnings about not blocking the fan..
So what does my setup REALLY look like, at least that's what everyone always wants to know.
My Teco FM-50 is mounted above my lathe on the wall, I screwed the FM-50 to a scrap piece of MDF that let me position the VFD where I wanted it while also being attached to the framing in the wall. The MDF happens to be painted white, it also had a hole cut in it, that's why it's scrap :-)The Grounding lug and connections are on the far left, then the 220 single phase input, the LARGE white and black wires. Its a line cord I am plugging into to a wall socket for now. A more permanent installation would likely use 12 gauge wire and include a neutral connection.
The 3 phase output is on the right rear, the white, black and yes, GREEN wires. I tagged the green wire at the motor with BLUE tape to remind anyone that opened it that the wire is HOT.. NOT ground. That setup will probably change over time. I didn't have any 4 conductor stranded cables long enough to reach from the VFD to the Mill right now..
The “hookup wire” I used for the remote control is some kind of old computer wire. It already had brass pins crimped onto the one end and those fit nicely into the 'TM2' connections on the VFD, so I just left the brass connectors on the wire. I do have more wires hooked up than I am actually using.
One thing that was nice about this cable is I could use the 8 primary colors for my connections. I made up a little chart as I was going along, Pin 3 = Fwd = Black, Pin 4 = Rev = White, Pin 5 = 12v = Red. So when I got to wiring up the switch and pot I could just follow the wire colors in my notes.
Here is the metal junction box with the magnet sticking to the mill's head. This box was missing all of the wire clamping hardware, so I just tied a knot in the cable as a 'strain' relief, which is perfectly fine to do for low voltage stuff like this. You don't want an accidental yank on the wires to be pulling on the switch and Pot's connections.
I had LOTS of green electric tape around the shop so I used that instead of Black tape, so where you see green tape, think BLACK tape.
The Pot is on the left and I was concerned that the terminals MIGHT short to the inside of the metal box as I was assembling, so I insulated them by running tape all of the way around the pot. You can kind of see the wires soldered onto the tabs of the pot. Green, Gray, and, Blue are connected to pins 10, 9, 8 on the VFD.
The center switch is the SPDT center OFF switch. It has the RED wire (12V) connected to the center and the Black and White wires, FWD and REV on the two ends. Again, that's all of the wiring you really need.
I wanted a 'JOG' button so I added the spring loaded momentary switch that is on the far right. The center connection of the momentary switch is wired back to the red (12v) line of the other switch and the Brown Wire which is Pin 6 (sp1) is actually programmed to be JOG. F 19 = 1. Which does not work correctly as wired because you also have to also power the FWD or REV lines to get the VFD to actually do a JOG.... That's for another day.
I went ALL OUT on the labeling.. Yes, sir, grab the nearest weird colored sharpie and start marking. I can take the lettering off and relabel this with a little Goof Off paint clean up stuff. So it's a fast, easy and modifiable labeling system.
And that's about all there is to it..Overall the VFD is a VERY cool device. I hope this write-up can help others to complete the setup quicker and with more confidence.
