Opinions needed! VFD, what brand and where to buy?

[EdK]

I can see a brake resistor being more useful on a lathe than a mill, but then I don't have a very big mill. An RF-45 clone.

Ed

[Bill Shields]

Even though I am a ONE MAN SHOP, there are multiple times when I have:

1> a friend in doing something (I have an apprentice in the shop fairly regularly)
2> two machines running at the same time.

This is particularly true when I have something running on the mill with the power feed / stop switch set so that I can walk away from it - or boring a hole with the power quill.

It isn't very often, but 2-3 times a month, I have at least 2 machines running for one reason or another.

If I had only one VFD, I would be screwed...and following Murphy's guidance, it would be at a time when I most needed to have both running because I was short of time.

Cost of a small VFD isn't really that much anymore, and by the time you put in a switch, it really isn't that much.

Look closely at sizing the VFD exactly as needed for each machine and dropping the switch.

A simple unit for a mill and maybe something a bit more 'tunable' for the lathe can get you where you need to go.

[lakeside53]

I also believe in 1 motor 1 vfd, but... that will generally come naturally to the user over time. Everyone needs to start somewhere!

On the last machine I built (3hp 2x72 belt grinder) I routed the VFD output to an L15-20R receptacle, then an L15-20P plug to the motor. It's very useful for rapid connection to random motors and equipment.

I find a mill like mine (2-3hp BP) takes a lot of tuning. I recommend the new adopter choose one brand and family of VFD. It's way too compicated for most to deal with several brands. I have 4 different right now, and even though I've been in this type of business for decades it can get painful at times. Hitachi and Teco I know well; ABB.. need to dig out the manual and actually read it each time.

[GlennW]

What was wrong with using a RPC since you plan to operate multiple machines?

[JTiers]

The braking resistor doesn't do any braking.......

What it DOES do is provide a place to dump the "returned power" from the motor. In some cases, the VFD uses power fast enough that a smaller motor can be stopped fast without any overvoltage shutdowns. or a larger motor can be stopped more slowly without an overvoltage shutdown.

ONLY if you want/need to shut down fast enough that you run into overvoltge issues is it necessary to put in a brake resistor.

Knowing a few parameters and details of the setup, many of which you probably do NOT know, it is possible to calculate the need for a resistor. Since you likely don't have the info, the best thing is to think about it and see what you get.....

Do you expect to NEED/WANT to stop the spindle in a hurry?

Is the spindle going to have heavy items (cutters or work) on it that you want to stop fast?

Would it be a problem to have a stop that is somewhat faster than a coast-down?

If not, you likely don't need a brake resistor. The drive will still do braking, just not as fast. You can buy a drive with no brake provision.

if you answered "yes", you MAY want one, and it would pay you to get a more expensive drive with the option so you can get it if needed.

Many low power drives do NOT have a brake provision, they start in the 3 to 5 HP range, maybe some 2 HP, depending.

OK.......

Now, about the resistor itself.......... I see a lot of folks with ideas how to get a cut-rate resistor..... and the manufacturers DO price them high. But you risk blowing out the braking circuit. I've seen stove elements, electric heater elements, even water heater elements recommended.

Any of those MIGHT work, but they might also do damage.

There will be a SPEC that gives the lowest allowable resistor, or the maximum current draw in the resistor. If you exceed the limits, you will probably blow out the IGBT, and then you will have no brake resistor EVER, unless you put on an (expensive) external controller.

[Patio]

What was wrong with using a RPC since you plan to operate multiple machines?

Hi Glenn

It was noisy and my machine has step pulleys. I like the idea of quieter running, and to be able to drill a hole with out having to change pulleys all the time. Guess I am lazy.

JTeirs
I don't even use the brake on the mill now, I save it for the day I may need it. For the same reason it would be nice to have a break for emergencies.

Everyone else.
I get the idea about about 1 VFD for 1 machine, and will probably end up there in time. I am getting the Hatachi for a 3 hp. out from a single phase input.

Thanks for all the information you all have posted, it has helped me to make a informed decision.

I am ordering it tonight and will post more as I get it set up and running.

[Patio]

The potentiometer controls the frequency. You might want a "jog" button and a locking emergency off. To get started you can just use the vfd front panel (which has a potentiometer on it).

The Hatachi Wj200-022SF that I am looking at from Drives Warehouse, does not show a potentiometer on the front. Am I missing something.
http://www.driveswarehouse.com/p-2527-wj200-022sf.aspx

[lakeside53]

There will be a SPEC that gives the lowest allowable resistor, or the maximum current draw in the resistor. If you exceed the limits, you will probably blow out the IGBT, and then you will have no brake resistor EVER, unless you put on an (expensive) external controller.

Yes... and there is also a duty cycle issue associated with the use of braking. Decent VFDs track the usage and give you programmable options on what to do if they are exceeded.

To clarify - my advise of the 50 ohm 300 watt braking is only applicable to the WJ200-022 the OP already said he was buying. That value is well within Hitachi's spec.

[lakeside53]

The potentiometer controls the frequency. You might want a "jog" button and a locking emergency off. To get started you can just use the vfd front panel (which has a potentiometer on it).

The Hatachi Wj200-022SF that I am looking at from Drives Warehouse, does not show a potentiometer on the front. Am I missing something.
http://www.driveswarehouse.com/p-2527-wj200-022sf.aspx

HA.. you are missing nothing. I am mistaken - they took it off and put the USB connection in its place. I use the WJ200-022 with the SJ200 remote operator (fancy name for the detachable front panel) and that has the pot on the panel. To be clear - I don't use the remote operator pot except for setup - it's a bit wimpy for generalised use.

You'll need a add a potentiometer - buy a decent brand linear 2-5K sealed type. Allen Bradley or similar work well. $5-10 on Ebay..

[Patio]

Lakeside53
Whew I feel much better now! I can get a potentiometer and buttons to make a remote for on the mill itself.
Thanks

[lakeside53]

Patio (and others). There is a "gotcha" in the manual... Starting around page 2-29 you'll do the inital setup. Unfortunately you cannot enter or even see some of the parameters because they neglect to tell you that they are blocked by register B037 "Function Code Display Restriction". The factory default is 04; you will need 01. This had me scratching my head for a while

When you are ready I can send you my list of parameters so you don't have to read 400 pages of manual. Although it's easy to get it "running", dealing with over-voltage and trip recovery does require some settings.

[lakeside53]

Here's my mill console. I used an old Sperry Univac box. The SJ200 detacheable front panel mounted to this gives me access to all the WJ200 functions without having to go to the back of the machine to fiddle with parameters and look at error codes. I usually leave it displaying rpm (scaled frequency), but I can also watch many other parameters. For example, motor current gives an indication of spindle load and insert wear.



The Buttons and Fwd/Reverse switch are Allen Bradley 800 series.

Here's the old SJ200 mounted in an old transfer switch box on the back of the mill. it now has a WJ200-022. This box is also my power distribution for a bunch of cnc stuff so there's a lot that doesn't have to be included for a basic setup. I have a 40 amp contactor to act as a single point of power off for the vfd and most of the external devices. The 300w "braking resistor" is at the top mounted to a big aluminum plate for heatsink; the bottom has a fan that runs when the spindle is on, and for30 seconds after it stops (programmed via the vfd relay outputs).




Bottom of box:



Side of box (these are high end breakers, not "light switches!". They are covered by a lexan flip cover to keep the chips uot.