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Doc Nickel
07-05-2008, 06:41 AM
I'm hoping to have my Nichols (http://bbs.homeshopmachinist.net/showthread.php?t=29473&page=3) reassembled by the end of the month, and so it's time to start thinking about a controller for the motor.

It has a 1HP 3-phase gearmotor, so I plan to use a VFD much like I did on my Sheldon. I love the capabilities of the system- speed control, soft start, etc.- but the AC tech MC1000 that came with the lathe is something like $400 or $500.

I've looked around a bit, but I'm still very new to VFDs, and not familiar with any of the manufacturers or individual models. So I'm looking for recommendations- not only of a specific model, but also a good dealer from whom to buy.

Specs: 1HP+, 240V single phase in, 240V 3-Phase out. Variable speed (frequency) and remote-mount control capable. Anything else is gravy. Cost needs to be low as possible for a good, reliable brand.

The guy that sold me the mill suggested Automation Direct, and a quick look brings up this unit (http://web1.automationdirect.com/adc/Shopping/Catalog/AC_Drives/GS1_(120_-z-_230_VAC_V-z-Hz_Control)/GS1_Drive_Units_(120_-z-_230_VAC)/GS1-21P0). That's not bad for $125, though I'm not sure what "volts per hertz" means.

Looking up the specs for the MC1000 note it's rated for "constant torque"- is this something to look for, or do most/all VFDs do this?

Oh, and I see some models have more or less external/exposed connections, assuming it'll be mounted in an enclosure of some sort. If at all possible, I'd prefer something pretty much ready to bolt right to the wall, and take internal/protected connections.

Doc.

Ryobiguy
07-05-2008, 07:36 AM
I'm looking around for a VFD myself, and I spotted this one: http://www.wolfautomation.com/Product.aspx?ProductID=19500

$166 for 1 HP sensorless vector drive. I think that'll be hard to beat.

I don't know how to clearly explain all the technical details, but volts/hz is more basic control and I believe you lose a lot of torque at lower speeds compared to a vector drive.

-Matt

quadrod
07-05-2008, 08:52 AM
i just got an www.automationdirect.com GS2 for my south bend 13. it has a 2 hp, 2 spd, 3ph motor. since i'm running it off of a generator till i can run
220v service out to my shed they said to get the GS2, a 2hp unit. i have to say that i'm very happy. it was very easy to install. it will do constant torque and you can set the ramp up from .1 to 600 seconds ( soft start ). the control panel is detachable and with a data cable you can mount the panel any where.
P.S. i set the soft start to 3 seconds and it will probably start faster if i want.

ammcoman2
07-05-2008, 09:35 AM
Factorymation http://www.factorymation.com/ in my opinion has very good prices on the TecoWestinghouse units. I now have 3 in my shop and am very pleased with the performance and ease of setup. Two are with 220v input and one with 120v. The latter is for a 1/2hp motor on a lathe.

Good luck in your quest.

Geoff

Bruce Griffing
07-05-2008, 09:42 AM
Sensorless vector units are much better than volts/hertz controls. The former is more of an active control whereas the latter is more or less dumb. I have had good luck with the LG (Lucky Goldstar) units, but I think any sensorless vector unit would make you happy. Shop around.

SGW
07-05-2008, 10:32 AM
www.vfds.com is another source.

lazlo
07-05-2008, 11:23 AM
the AC tech MC1000 that came with the lathe is something like $400 or $500.

AC Tech is made in China (but according to the guys on PM, they're pretty decent) -- they're the least expensive VFD's you can buy.


Looking up the specs for the MC1000 note it's rated for "constant torque"- is this something to look for, or do most/all VFDs do this?

All do. Or more accurately, a consequent pole induction motor (i.e. most common AC induction motors) is a constant torque device, and power varies according to the motor's RPM.


I'm not sure what "volts per hertz" means.

VFD's operate by modulating the frequency of the voltage applied to the motor. So VFDs convert the fixed-frequency supply voltage to DC, then pulse-width modulate a continuously variable frequency to set the motor speed. If your motor is 1725 RPM nominal at 60 Hz, the VFD will drive the motor-side line frequency at 30 Hz to get 863 RPM. But since the horsepower rating of an induction motor is at its nameplate speed, you get half the horsepower at 1/2 the frequency/RPM. That's why people typically double the horsepower of the motor on a VFD vari-speed conversion.

Bruce mentioned sensorless vector, which the AC Tech VFD linked has.

A sensorless vector or flux vector drive is a closed-loop feedback system that emulates a vector/servo drive. Since there's no encoder on the motor, the VFD senses changes in the load circuit to guesstimate the amount of slip and make changes in the VFD output with a PID loop to improve speed or torque control. A typical VFD has a rated speed and torque control range of 20:1. A sensorless vector VFD has a 200:1 speed/torque control range. Put an encoder on the motor, and you've got a full vector/servo motor, with a speed/torque control range of 1,000:1.

Since you've got a mechanical gearbox driving the horizontal, I'm not sure how much sensorless vector will help you. I've got a VFD on my Clausing lathe, which has a hydraulic Reeves drive. So I set the VFD to 60Hz, and use the mechanical vari-speed to adjust the spindle speeds.


Specs: 1HP+, 240V single phase in, 240V 3-Phase out. Variable speed (frequency) and remote-mount control capable.

All modern VFD's will have those features. I'd double check the cable interface of the remote mount. The display panel comes off the VFD, and you have to wire a proprietary cable from the VFD to the remote unit. Check the price of the cable -- the Hitachi that I have is over $100 for a silly cable with proprietary connectors. The Mitsubishi VFD I have uses a standard Ethernet cable.

The other feature you might consider is the additional driving transistor for an external braking resistor. The lower-end units don't have this, so you have to buy a braking "module" (with the extra IGBT), which is big $$$ (usually as much as the VFD).

RobbieKnobbie
07-05-2008, 11:40 AM
The Automation direct inverters are a good unit for a very attractive price.

For a lathe (or mill) application you don't really need vector drive. If you're going that slow you're probably in a low gear anyway, so the linear torque loss below 60hz is not relly too much of an issue.

The A.D. drives do not require a seperate breaking module to fit a breaking resistor (which is a very nice thing to have in an emergency). In fact, I fitted two common stove elements in series and wired them directly to the dbr terminals on the vfd and was able to cut the decel time to .5 seconds. That's the time the vfd brings the motor+load to a stop from full speed. (on a lathe you'll need to give it more time due to the added mass of the spindle etc compared to a mill). If you don't allow enough decel time in the frequency drive it will just trip out and let the motor drift to a stop as if it were running on a simple switch.

Automation direct GS2 drives can be mounted remotely, though for a really nice installation you can set up a pushbutton box with all the common commands, run, stop, e-stop, reverse and speed pot. Then you can put the VFD safely in an enclosure or the base of the machine or something.

I've installed half a dozen AD drives, in my own shop and at work and I've never had any issues with any of them. They're a very good basic drive.

RobbieKnobbie
07-05-2008, 11:56 AM
The guy that sold me the mill suggested Automation Direct, and a quick look brings up this unit (http://web1.automationdirect.com/adc/Shopping/Catalog/AC_Drives/GS1_(120_-z-_230_VAC_V-z-Hz_Control)/GS1_Drive_Units_(120_-z-_230_VAC)/GS1-21P0). That's not bad for $125, though I'm not sure what "volts per hertz" means.
Doc.

I just looked at the specs on the GS1, and it doesn't seem to offer dynamic breaking on that model. For $25 more (149) you can get the GS2 that will allow breaking as I described above.

The features available on the gs2's are really nice, and while you said 'anything else is icing on the cake,' you'll be glad to have some of them. Configurable inputs, choice of decel rates (one for regular stopping, one for emergency stopping) and stuff like that make them a pleasure to use.

I'm not saying AD is the only drive that offers these features - not at all - but I think they're the only ones to offer all them at this price. I am not in any way connected to AD other than being a VERY happy customer.

murph64
07-05-2008, 02:06 PM
... But since the horsepower rating of an induction motor is at its nameplate speed, you get half the horsepower at 1/2 the frequency/RPM. That's why people typically double the horsepower of the motor on a VFD vari-speed conversion.


So I'd want a 2HP VFD if I want my 1HP motor to run the same as it did when connected to "real" 3Ph power?



Andy

lazlo
07-05-2008, 02:20 PM
So I'd want a 2HP VFD if I want my 1HP motor to run the same as it did when connected to "real" 3Ph power?

No. If your machine came with a motor that generated 1 HP at 1725 RPM, then the VFD would drive the motor with the same power.
But if you want to use the VFD as an electronic vari-speed, then the induction motor will be at 1/2 HP at 863 RPM, and 1/4 HP at 431 RPM.

In other words, a VFD is not a gearbox.

But if you traded-up to a 2 HP induction motor, you'd have 2 HP at 1725 RPM, 1 HP at 1/2 of normal speed: 863 RPM, and 1/2 HP at 431 RPM. That gives you an extremely wide operating range without changing belts.

murph64
07-05-2008, 02:39 PM
http://lethaleuphoria.files.wordpress.com/2008/02/lightbulb_dramatic.png



OK, it makes sense now...Thanks.


[/hijack] :D



Andy

S_J_H
07-05-2008, 04:58 PM
I have had a automation direct gs2 for a few years. Flawless performance, easy to use. It's now driving the cnc bench lathe that I built and is under full computer control. That was also very easy to hookup using a simple add one board.

Great unit for the price.
Steve

Carl_In_NH
07-05-2008, 07:12 PM
I second the recommendation for www.factorymation.com and the Teco units. I've purchased two FM50 VFDs from them - a 3HP unit for my Pratt & Whitney lathe, and a 1HP unit for my surface grinder. The 3HP unit was about $180, and the 1HP voltage-doubler unit (so I could run the grinder off a single phase 110V input) was about $120. I'm really pleased with both of these VFD units.

I've also got a Minarik VFD on my Rockwell milling machine; I don't like that one at all. It has a lower switching frequency that causes the motor on the machine to sing at 4 KHz - which is as fast as its internal switching power supply will go - unlike the Teco - which are 16 KHz, if memory serves. It also creates high voltage spikes and hash that drive my DRO nuts on that machine. Chances are very good that I'll just toss this Minarik in the trash and order another Teco to replace it.

Standard disclaimers apply - no connection to Factorymation other than as a happy customer.

-Carl

PaulT
07-05-2008, 08:16 PM
I've bought several Teco units from www.dealerselectric. and have been happy with them. One good thing about the Teco's is they are setup to add a braking resistor without buying an additional "braking interface", some VFD's aren't. With the Teco's this means only an additional $30. gets you resistor braking, which is definitely worth it, this makes the Teco's some of the best deals out there. I never touch the brake lever's on my mills anymore, the VFD brakes the spindle very smoothly in about 1 sec, same deal on my lathe.

Just to be clear, most VFD's made these days at 3HP or less are spec'ed to supply full power with either 3 phase or single phase in, so you don't need to derate them if you only have single phase.

Paul T.

ammcoman2
07-06-2008, 09:32 AM
In Lazlo's last post he mentioned the derating as rpm's are lowered.

For my conversion to 3 phase on my mill I lucked out on a virtually new 1hp, 1140rpm, 145T frame Westinghouse motor at a flea market. It replaced the original single phase 1 1/2hp, 1725rpm motor and is physically every bit as big (65lbs)

My reasoning to get this 6 pole(?) was to get low rpm torque and I can always set the max frequency higher than 60Hz if I need to. Of course the other huge benefit is how smooth this "new" motor is and the ability, even without an external resistor, for the VFD to stop the spindle fairly quickly.

Geoff

nheng
07-06-2008, 09:48 AM
I bought a Teco EV50 from www.dealerselectric.com for an incredible $120 for a sensorless vector model (with 120v single phase input). It has behaved very well so far (except for my VFD shocker thread) and on a 1hp Bridgeport. Loading the driving pulley by hand (VERY careful use of a block of wood), I have been unable to alter the RPMs at very low speeds (10Hz or 1/6 of normal).

The thing is tiny and the range of inputs is good. Enough inputs for speed control pot, forward, reverse, jog, and emergency stop switches.

Also have had good success with a Hitachi L100 on my 3hp lathe motor for several years. The only thing I don't like about the Hitachi is that there is no direct input for an emergency stop. If I went with Hitachi going forward, it would be with a sensorless vector model but that's when Teco prices took over :) Den

lazlo
07-06-2008, 12:25 PM
For my conversion to 3 phase on my mill I lucked out on a virtually new 1hp, 1140rpm, 145T frame Westinghouse motor at a flea market.

My reasoning to get this 6 pole(?) was to get low rpm torque and I can always set the max frequency higher than 60Hz if I need to.

Good deal Geoff :) The 6 pole motor will have 50% more torque than the stock 4 pole motor.

You can get the same torque with a 3450 RPM (2 pole) motor by ratio'ing the drive pulleys, but the 1150 (6 pole) or 1725 (4 pole) motors give you more flexibility in over-speeding the motor.

NEMA motor bearings are rated for 4,000 RPM, so you can safely overspeed a 1150 or 1725 RPM motor by 100%, but there's not a lot of headroom on a 3450 RPM motor...

lazlo
07-06-2008, 12:29 PM
Also have had good success with a Hitachi L100 on my 3hp lathe motor for several years. The only thing I don't like about the Hitachi is that there is no direct input for an emergency stop.

Den, that's the one VFD that's been mentioned that I wouldn't recommend :p

The Hitachi L100 was my first VFD -- bought it from Dealers. Aside from the lack of a dedicated E-Stop input, it also doesn't have the interface for an external braking resistor, and the Hitachi braking modules are several hundred dollars at Dealers.

The L100 series is cost-engineered -- the J100 series has all the features a VFD is supposed to :)

lazlo
07-06-2008, 12:35 PM
I bought a Teco EV50 from www.dealerselectric.com for an incredible $120 for a sensorless vector model (with 120v single phase input).

I just bought the Teco Evo101 from Dealers for my Tool and Cutter Grinder. I was getting tired of swapping 220V cables, so it's nice to be able to drive a 3 phase motor from a common household outlet :)

My Evo is on it's way, but I'm pretty sure the EVO series and the N3 series are also made in China. The FM series is made up the road in Austin :)