Suggestions for a VFD

Hi all,
I have a surface grinder that I recently brought home and would like to put some power to it. It is an old Covel with a 3/4 HP 3 phase motor.
How do you size thse things for your application ? Should I be looking at something rated for 1HP ? Any Brand names to look for and any to stay away from ?

TIA,
Kerry

You only need a 3/4hp VFD.

Hitachi VFDs are pretty good, I have an SJ200 on my old covel surface grinder. It's actually hooked up to both my mill and the grinder using a drum switch to select between them. You can put as big of a VFD as you like on there so long as it has settings that allow you to use a smaller motor. I think my hitachi has settings for anything down to 1/4 HP and up to 3 HP. The motor on the grinder is 1.5 hp. With a motor that small, you can get VFDs that take in 120 single phase and crank out 220 3 phase. I think anything up to 1hp takes in less than 15 amps @ 120v, so you could run it on a standard 120v outlet if needed. If you have 220v, I'd get the biggest VFD you can afford because it will have heavier duty parts in it, and if you want to run something else with it in the future with a bigger motor, you can. It seems that the 2hp is the line where they start to get more expensive, and anything above 3hp they get REALLY EXPENSIVE. Up to 2 hp, they're only a few $$$ for bigger ones. I think you can get a 2hp L200 for $150.

I have one that is 2hp rated on 3 phase and it will do that easily.I will take 75 for it. I used it several times on a horizonal saw but changed the motor to single phase so i could wheel it around the shop and plug it in at any wall receptical. Jim


I will need to look to see what it is.Cant recall now...

Ok here it is.It is a AF-3000 G11. It is 10.1 amp and 2 hp rating.230


I originally purchased it to run my surface grinder .I Discovered that I still had 2 other 3 phase motors on the grinder.The coolant pump and the hydrolic pump! This is way less than I paid for it.It is never going to get used sitting in the cupboard..

Well that's a good deal!

There you go, that's a good deal for a VFD.

j king said:

I have one that is 2hp rated on 3 phase and it will do that easily.I will take 75 for it. I used it several times on a horizonal saw but changed the motor to single phase so i could wheel it around the shop and plug it in at any wall receptical. Jim


I will need to look to see what it is.Cant recall now...

Ok here it is.It is a AF-3000 G11. It is 10.1 amp and 2 hp rating.230


I originally purchased it to run my surface grinder .I Discovered that I still had 2 other 3 phase motors on the grinder.The coolant pump and the hydrolic pump! This is way less than I paid for it.It is never going to get used sitting in the cupboard..

Click to expand...

J king,
what is the input requirements ?
I have 220 1phase here at home .
Kerry

JunkyardJ said:

Hitachi VFDs are pretty good, I have an SJ200 on my old covel surface grinder. It's actually hooked up to both my mill and the grinder using a drum switch to select between them. You can put as big of a VFD as you like on there so long as it has settings that allow you to use a smaller motor. I think my hitachi has settings for anything down to 1/4 HP and up to 3 HP. The motor on the grinder is 1.5 hp. With a motor that small, you can get VFDs that take in 120 single phase and crank out 220 3 phase. I think anything up to 1hp takes in less than 15 amps @ 120v, so you could run it on a standard 120v outlet if needed. If you have 220v, I'd get the biggest VFD you can afford because it will have heavier duty parts in it, and if you want to run something else with it in the future with a bigger motor, you can. It seems that the 2hp is the line where they start to get more expensive, and anything above 3hp they get REALLY EXPENSIVE. Up to 2 hp, they're only a few $$$ for bigger ones. I think you can get a 2hp L200 for $150.

Click to expand...

I kind of like this idea, as I can get my mill off of the static convertor and get full power out of it.
I see an L200 3HP rated for 265.00$ at Drivewarehouse.com

Just so you know, the L200 is straight V/Hz.

The L200s aren't "vector" type drives, they simply vary the speed by cranking out X ammount of voltage @ X frequency according to the way they're programmed. They don't have the capability to sense feedback from the motor like a vector drive does in order to boost low speed torque. On things like a mill or a lathe, this can be a GOOD thing. On a surface grinder, it doesn't really do anything. The SJ200s are vector type drives, but they're not made any more. I forget what the new line of hitachi vector drives are called. I'm not sure if they support dual motor profiles like the SJ200s and L200s do, which alters the settings of the drive for the different motors. I THINK they do though.

I don't really see a need to alter the freq. output. I just want 3 phase power to run the machines on all 3 phases. The surface grinder can turn it's normal rpm at 60 Hz and that will be just fine. The mill is a vari-speed anyway and rpm would still be controlled through that mechanism.

Or am I missing the boat with something here ?
Won't you get full rated output from the motor at it's designated voltage and Hz when supplied by the VFD ?

Mr. O said:

Won't you get full rated output from the motor at it's designated voltage and Hz when supplied by the VFD ?

Click to expand...

Simple VFDs control motor speed by varying the line frequency. If you set one up to output at 60 Hz, you will get nominal motor speed.

One thing to watch out for regarding VFD rating:
They're all(?) designed to drive a motor of rated HP when fed from 3-phase power.

Some will work with single-phase AC input, but with a reduction in drive capability of 50% (usually). For example, to drive a 1 HP motor from a single-phase supply, you would need a VFD rated 2 HP.

Some are rated ONLY 3-phase input. It may or may not be possible to run one of these on single-phase power. I wouldn't suggest doing it.

Best to double-check the specs of any candidate before making a commitment.

- Leigh

Yes, you will.

Well, if all you're using it for is a phase converter, you're kinda wasting some $$$. You could get a 5hp idler motor, and use some of the parts from your static phase converter to build a RPC, and you can run both machines at the same time if you wanted. That's probably what I'd do in your position if the mill is variable speed. Then any machine you get from now on can be wired up. That will also give you 100% power output. It would also be easier to wire up than putting a drum switch on the output of the VFD, and setting each machine up with the start/stop controls for it. You can just use the machines like they were on regular 3 phase power.

A vector type VFD is actually capable of driving the motor in such a way that it cranks out MORE THAN 100% torque at low speeds. It's a nifty feature, when the VFD senses that the motor is starting to "slip", it alters the output in such a way to help it maintain speed. Where a regular VFD will allow the motor to "slip" more and more as the load increases. It works really good on machines that don't have mechanical variable speed.

You'll get 100% power output from any VFD at full motor speed.

The real Leigh said:

Some will work with single-phase AC input, but with a reduction in drive capability of 50% (usually). For example, to drive a 1 HP motor from a single-phase supply, you would need a VFD rated 2 HP.

Some are rated ONLY 3-phase input. It may or may not be possible to run one of these on single-phase power. I wouldn't suggest doing it.

Best to double-check the specs of any candidate before making a commitment.

- Leigh

Click to expand...

Leigh is right. For example, While most of the TECO 3 hp and under VFDs will drive a motor to 100% power on single phase or 3 phase, there are other VFDs that are not rated for 1 phase input and that requires one to "Derate" the VFD if you want it to work.

If you want to power 3 machines from a single converter, get a RPC.

Teco VFD - Sensitivity

Just got a Teco VFd for my bridgeport mill and find the sensitivity to be too great. Does anyone know how to program these things to be less sensitive?

Sensitivity to what?

find the sensitivity to be too great.

Click to expand...

Some drives use a speed pot to adjust the freq up & down, which is adequate for most users. Other drives have a keypad with an up/down touch switch. The keypad lets the user adjust freq up or down in increments of 0.1 Hz (on my SMVector drives). I cannot tell that 0.1 Hz makes any change, as that is only 3 rpm difference at the motor shaft.

On Target

In my opinion, you are on target with a VFD. I have used both static phase converters(POS), rotary phase converters, an VFDs. The VFD is the way to go. Set it and forget it. I just put a TECO on an old Baldor 3/4 HP buffer. I wanted variable speed and this was the only good way I knew to do it. They work great. Programing it is over my head. I set the parameters that were were important and did not worry about the rest. Something else you can do is use it to brake the motor which, in my opinion, would be nice in a surface grinder.

I am going to add a VFD on my surface grinder for the same reason you are. I have been running it on a rotary phase converter along with my lathe. I am installing a VFD for convenience and the braking ability. Something to keep in mind, the VFDm should be wired directly to the motor.

My lathe is a Nardini 1440E with a 6HP two speed motor. I have a 5 HP Baldor Super E and a Hitachi vector drive sitting on the shelf. I am going to make the conversion as soon as I have time. I will eliminate several contactors and two miles of wire plus having a variable speed machine. The parts to fix the brake on my lathe were over six hundred bucks. I bought the motor, vector drive, and braking resistor for less than the parts to fix the brake.

FYI-my lathe will be three phase in and three phase out. The buffer is 220 single phase in and my surface grinder will also be single phase 220 in.

Good luck and let us know how it turns out.

grits

Keep it simple

There are a number of small VFD's available that will run a 3/4hp 3 ph motor off a common wall outlet. Automation direct has one for $125 that would be more than adequate for your needs. (there are other brands, but I've used a couple of the A.D.'s and had good success with each)

For most common shop needs a simple v/h drive (as opposed to vector type) is perfectly adequate and somewhat less expensive.

Considering the low cost of each drive, I'd stay away from wiring multiple machines to one vfd. You're better off keeping the control for each machine *at* the machine rather than mounted on the wall between two machines.

J King:
Did you ever sell your 2 hp rated vfd phase converter? I need one for an old Leblond lathe.
Thanks