New 1340GT Coming and Need Assistance with VFD

wrmiller · Jan 7, 2015

Hello all,

I will be receiving my 1340GT later this month or so and thought I'd ask some questions of Mike (zmotorsports) and others that have knowledge of this stuff.

My lathe motor is a single phase, but am getting a Leeson 3-phase motor and Hitachi VFD from Matt to go on the lathe. Question is, how exactly do I go about that?

Mike, when I read (and re-read) your thread I saw that you pulled much of the factory electrics out of the control box, but kept some. May I ask what you did and why (simple question but may not be a simple answer, I know)? I didn't even know what a 'contactor' was until I joined this form, but I do understand relays and switches.

What was the pot you used on the front panel, a 1k? Do you remember the make/model? What gauge wire do you need to run? And I'm not sure what/how you did the jog and fwd/rev switch. Are these control lines into the control portion of the VFD that you simply ground via a switch to make them active?

As you can see, I'm starting from a complete position of ignorance here as I'm not an electrician but more of a digital guy. :dunno:

Any and all help would be greatly appreciated, thanks guys. I'm hoping Ray sees this thread as well.

mksj · Jan 8, 2015

Hi Bill,

The 3 phase motor should already be installed on the lathe. You will need to mount the VFD either in the lathe cabinet below the motor or in a separate wall mounted cabinet, as the machine control box is very small. After you have programmed and set-up the VFD, you do not need routine access to the VFD controls or display. Matt will send you a 1K pot and knob with the VFD, otherwise send me a PM with your address and I will send you one that I have. There is a fairly extensive description of the installation and programming here http://www.hobby-machinist.com/show...s-to-the-control-switches-on-a-PM1340GT-lathe or download this file http://www.hobby-machinist.com/attachment.php?attachmentid=87276&d=1415299403 .

The main power wiring to the VFD should be 12G (12/3 SOOW Power Cord, or 12/4 if you need 120V at the machine), you should have a service (power) disconnect before the VFD either on the machine or in the electrical cabinet housing the VFD. If using a separate electrical cabinet, I would use a 30A 2-pole 240V breaker. The electrical cabinet should be at least 4X the volume of the VFD and vented (cut holes) on the bottom and/or add a small fan. If you mount it in the lathe cabinet, no cooling holes are needed. Depending on the DRO, you may need 120V at the machine. The light provided with the lathe is 24V 50W (AC or DC), so you either need to retain the stock AC transformer (easiest) in the control box to power the light or replace it with a PWM 24V DC power supply. Depending on your set-up, you will need one or more relays for controls, these come in AC and DC 24V versions. I recommend wiring as Mike has posted which uses the VFD's own 24 VDC power to drive the 4P 24VDC relay. You wire the controls as shown in his diagram and make the connections at the switch block in the control box. You need separate wiring for the speed control.
http://www.hobby-machinist.com/attachment.php?attachmentid=88283&d=1416750164
http://www.hobby-machinist.com/showthread.php/24887-My-Precision-Mathews-PM1340GT-Arrival

Braking resistor, 100ohm (~200-500W) is required if you use VFD braking: http://www.ebay.com/itm/231133634736?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT (this one is rated at 120W unmounted, 500W if mounted to a metal heat sink (so mount it on the cabinet or metal surface, run the wires to the designated VFD terminals).

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Power cable between VFD and motor (shielded 14G 3 wire + ground), shield is grounded at the VFD: http://www.ebay.com/itm/56-Helukabe...779?pt=LH_DefaultDomain_0&hash=item1e97f06bfb

Relay 4P, 24VDC: http://www.automationdirect.com/adc...81_-z-_782_-z-_783_-z-_784_Series)/784-4C-24D

Relay 4P mount: http://www.automationdirect.com/adc...ts_-a-_Accessories/Relay_Sockets/784-4C-SKT-1

Crimp connectors, 22G for control wire at VFD: http://www.ebay.com/itm/100Pcs-22-A...688?pt=LH_DefaultDomain_0&hash=item2a48f94b28

Diodes, 1N4004 (just about any diode 1N4001-1N4008). http://www.ebay.com/itm/100x-1N4004...097?pt=LH_DefaultDomain_0&hash=item3f433b8631

Control cabling between the VFD and terminal block in the control cabinet, you can use any 22-26G bundled wiring. I prefer 22G as it is less fragile, and use the 22G crimp connectors at the VFD end (either crimp or solder to the control wires). The wiring between the speed pot and the VFD should use 3 or 4 wire shielded cable, ground the shield at the VFD. This reduces noise pick-up in the cable which can be an issue because of the VFD electrical noise.

You might also consider having QMT install the VFD, as I understand that is an option.
Mark

wrmiller · Jan 8, 2015

The Leeson motor is being bought separate. The motor on the lathe is a single-phase. And I just sent an inquiry to Ray asking how much Matt would charge to install the motor and VFD. I didn't think of that, thanks.

And thanks for all the help. I have already downloaded/printed the programming guide. Much appreciated.

zmotorsports · Jan 8, 2015

wrmiller19 said:
Hello all,

I will be receiving my 1340GT later this month or so and thought I'd ask some questions of Mike (zmotorsports) and others that have knowledge of this stuff.

My lathe motor is a single phase, but am getting a Leeson 3-phase motor and Hitachi VFD from Matt to go on the lathe. Question is, how exactly do I go about that?

Mike, when I read (and re-read) your thread I saw that you pulled much of the factory electrics out of the control box, but kept some. May I ask what you did and why (simple question but may not be a simple answer, I know)? I didn't even know what a 'contactor' was until I joined this form, but I do understand relays and switches.

What was the pot you used on the front panel, a 1k? Do you remember the make/model? What gauge wire do you need to run? And I'm not sure what/how you did the jog and fwd/rev switch. Are these control lines into the control portion of the VFD that you simply ground via a switch to make them active?

As you can see, I'm starting from a complete position of ignorance here as I'm not an electrician but more of a digital guy.

Any and all help would be greatly appreciated, thanks guys. I'm hoping Ray sees this thread as well.

Bill, a contactor is merely a relay that controls the load (large gauge wiring) by means of switching a control circuit (small gauge wiring). This enables you to control high amperage loads via smaller amperage (read less expensive) wiring and switches.

You will need to feed the VFD from a 230-volt source, two hot legs and a ground from your breaker panel with 30-amp breaker will be sufficient. I recommend a little extra measure of running those two hot wires through a two pole fused block and a disconnect. You can use a large motor starter but that is really overkill, I merely used a double pole/single throw Square D brand ON/OFF switch to control power just before the VFD. This also feeds my 240 VAC to 24 VAC step-down transformer that I retained from the original electrical box on the lathe to feed my light. It is easy to remember to turn off that way because as soon as I turn my switch on to power the VFD, my light on the lathe comes on. Great to help remind me to turn the switch off, if closing up the shop and the lathe light is still on it means I forgot to turn the switch off for the VFD.

The VFD will take the place of all of the switching of high amperage load and so therefore the contactors are no longer needed in the electrical panel. You simply will run 4 high amperage wires, 3 for the current carrying and one for the ground (usually ground will be green) from the output of the VFD to the motor. DO NOT, and I repeat, DO NOT go the 3phase from the VFD directly to the plug or wiring that the lathe will come with, it must be connected directly to the motor. Once you do that I recommend you fire up the VFD and run the motor via the touchscreen/pad on the VFD just to make certain everything thus far is connected properly and the motor runs. Mark mentioned using 12 gauge wiring, which is fine for the amperage, I used 10-gauge as I had some left over from my 10k pound two-post lift installation. The connections will be as follows from the VFD to the motor, 3 current carrying wires and a ground from your NEMA enclosure to the motor housing. I would also include a ground from your breaker panel to the NEMA enclosure just to be safe.

From the VFD to the control portion of the lathe I did as Mark mentioned above, I used the 24 volt feed from the VFD to run through all of my controls. This is my directional/rotary switch as well as E-stop and JOG features. The use of 22-gauge wiring is fine. I used a 22-gauge/10-conductor loom to go from the VFD to the lathe control panel for all of this.

Once the wiring is completed as per my schematic which then you have to go into the VFD by means of the programming section in the manual and tell the VFD what signals to look for and what to do when the signals are seen. Such as JOG, forward or reverse. Keep in mind you don't have to run the JOG function like I did, I merely wanted this function but it is not necessary. Nice to have but not necessary.

I hope that helps and didn't confuse you. Mark, aka mksj, did a fantastic write-up on his installation which is probably better than mine. I would read through it very thoroughly.

wrmiller · Jan 8, 2015

As you said, just another name for a control relay. Got it, thanks.

I will read and re-read yours and Mark's install notes.

zmotorsports said:
Bill, a contactor is merely a relay that controls the load (large gauge wiring) by means of switching a control circuit (small gauge wiring). This enables you to control high amperage loads via smaller amperage (read less expensive) wiring and switches.

GA Gyro · Jan 8, 2015

THX for starting this thread: I have a 1340GT coming in this January batch, mine will have the factory 3PH motor on it.

I plan to get the VFD from Matt, may give him a call and ask him how he mounts it.
OTOH: may do a custom install... have not decided yet.

I have a tookbox I found at Harbor Freight (damaged slightly, got it for a good price):

http://www.harborfreight.com/tool-s...4-lb-capacity-glossy-red-tool-cart-61427.html

I removed the box from the cart and plan to mount it below the chip pan. If I mount the box to the right, this will leave about 9-10" of free space between the two stand cabinets and the 'hanging' toolbox. Was thinking to find an elec box to put down there...
(Need to sand the gloss off the front of the red toolbox and paint it Rustoleum 'royal blue'... the color I have more or less adopted to use with (and eventually repaint the blue part) my PM machines.

Will be watching this thread... THX again for starting it!

John

mksj · Jan 8, 2015

One correction to the above information, the WJ200-015S takes a 50 Ohm brake resistor (the 100 ohm mentioned was for a smaller installation). I installed a 500W version. Since the duty cycle for the lathe braking is very low, you do not need a huge resistor for braking. Something along the lines of this http://www.ebay.com/itm/500W-50ohm-...325?pt=LH_DefaultDomain_0&hash=item35ce35a6ed , the price seems to vary, I paid $26.

There are other vendors and various types of open resistors (tubular wound types) like Surplus Sales of Nebraska. http://www.surplussales.com/Resistors/WireWound/WW50-699.html , something along the lines of the (RWM) 26-136-50R 400W Milwaukee 26-136 Ribonwound, 1-5/8" x 8-1/2" if you mount it in your electrical cabinet. There is around 360+ volts going to the resistor terminals, so be very careful when installing these type of resistors.

wrmiller · Jan 8, 2015

OK, ignorant question number one: What is a braking resistor and why do I need it? Is it used to act as a load for the back EMF the motor produces as it spins down un-powered?

JimDawson · Jan 8, 2015

wrmiller19 said:
OK, ignorant question number one: What is a braking resistor and why do I need it? Is it used to act as a load for the back EMF the motor produces as it spins down un-powered?

Your're close, it adsorbs the back EMF while the motor spins down under controlled deceleration. It allows the motor to decel faster under VFD control. It keeps the DC buss from going over voltage. Unpowered, there is no back EMF, or at least very little.

wrmiller · Jan 9, 2015

JimDawson said:
Your're close, it adsorbs the back EMF while the motor spins down under controlled deceleration. It allows the motor to decel faster under VFD control. It keeps the DC buss from going over voltage. Unpowered, there is no back EMF, or at least very little.

Thanks Jim. It was just a SWAG (scientific wild-arsed guess) as we use the spindle's back EMF in disk drives to power shut-down circuits and get the data to a safe place in an emergency. So the combo of the resistor and VFD actually 'brake' the spindle and bring it to a stop sooner? Poor mans foot brake?

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