Deckel FP1 motor question

[Jackson Sowell]

I posted this question in the VFD section. Thought I'd maybe have better luck posting it here.
I've purchased an FP1 which has a 460 volt 2-speed motor. I only have 220 single phase. I'm thinking I should get one of the VFD/motor packages like dealers electric offers. Should be relatively easy to mark a couple of speeds on the VFD to duplicate the factory-input speeds and use the machine otherwise as designed.
What do you guys think. Good idea, bad idea, or is it a yeah, but? I welcome any input. Like to avoid making an expensive mistake if possible. This is the best idea I could come up with.
Thanks in advance to all who reply.
Jack

 

[Sean S]

Jack,
Could you tell us what items you have, or plan to have in your shop that could have special power requirements?
That might effect the best answer.

Sean

 

[Jackson Sowell]

At the moment, the Deckel is the only thing needing 3-phase. The other equipment I currently have is single-phase, though that may change later.
Though I would prefer to have three-phase supply, I don't believe it's in the cards. IF I get to move to a new place in a few years, I'll make sure to have 3ph, but for now I'm having to make do as best I can. I'm trying to stay within my budget now and hoping for improvement later. Fortunatley I'm not interested in large projects, so smaller machines are usually available with smaller single-phase motors.
I guess I could put a 220 volt single-speed, single-phase motor on the Deckel, but if I can swing it, I'd like to avoid cutting my available speeds in half. Is there a 2-speed single-phase motor available which would work? (I believe I've already acknowledged my ignorance on matters electrical)
Best regards and TIA,
Jack

 

[Forrest Addy]

Without knowing more about the installation I can reccommend the 2 HP VFD package sole by Dealer's Electric. The VFD is single phase rated so you can run a 230 Volt curcuit and hook it up in your single phase shop. The motor is a 143 T frame which is huskier than the 56 frame usually found in budget 2 HP induction motors.

http://www.dealerselectric.com/

If your existing motor is 460 only you're sunk unless you have a talented local motor guy who can reconnect the internal windings to 230 Volts. There's a lot of "it depends" connected with reconnecting a foreign built motor for lower voltage.

Since the Deckel is metric you'll have to to suffer through the shaft, center height, bolt pattern hassle but that's a small deal.

As for two speed Vs VFD drive, there's a VFD parameter you can set to halve (or any other fraction) the set RPM by flipping a switch. I wouldn't have a 2 speed motor if I could run the machine from a VFD. There are exceptions where the motor is built into the machine or dynamite reversal is required but otherwise...

By the way keep the step pulleys and geared transmissions. You need them. If you halve the motoro RPM you have its HP because a motor developed constant torque. If you halve the RPM with belts or gears the HP stays constant and the torque doubles. It's ration and proportion meets home shop physics.

 

[Sean S]

Just a small addition to that....

The motor platform on the FP1 is adjustable for height as I'm sure you have already seen Jackson. In most of the VFD upgraded Bridgeport packages I've seen, they swap out the original 2hp motor for a 3hp...presumably to counteract the torque loss in the low ranges from no longer using the pulley system.
I don't know how large a motor you could fit in there, but it is an option. I find however that the stock 2hp is plenty for the machine and you always have the gear reduction as Forrest says if you need more torque.
I gather that you do not have a lathe yet? It's true that you may have a small mating problem with the shaft of the new motor and the original pulley... perhaps a local machine shop could help you fit that.

If you end up going this route, take a bunch of pictures if you could and keep notes.
I for one would be very interested in the results.

Sean

 

[Forrest Addy]

Sean:

"...presumably to counteract the torque loss in the low ranges from no longer using the pulley system."

You still need the existing pulley system in any machine tool converted to VFD to take advantage of the machine's full spindle HP and RPM rangibility.

The VFD doesn't replace the pulley system; it adds all the speeds between the pulley steps and adds many convenience features. For instance spindle braking, lower power consumption, spindle braking, very low speed operation for tapping, long sweep fly cutting, form cuts, and flexibility of operation.

Naturally, you can run the VFD at lower RPM with the belt or gears set a higher speed forlow HP operations. If you wish to expoit the machine's full HP potential you'll still have to make use of the machine's belt and gear settings.

 

[Sean S]

I wont disagree Forrest, but many complete VFD Bridgeport conversions replace the vari-speed pulley setup with a 1:1 non-moving pulley setup and some even place the motor directly over the spindle, bypassing any pullies at all.
Almost all "OEM" conversions I've seen replace the stock 2hp motor with a Baldor "Super-E" motor in 3hp.

In the case of the Bridgeport, I think most people actually do the conversion to be rid of those pesky plastic bushings that plague that vari-speed system.

In the case of the Deckel.. well, you cannot replace the gears even if you wanted to. The only pulley in a Deckel is the one that drives the geartrain and is there only to transfer power.

I can sure see how a VFD combined with this lathe-like geartrain would give someone a whole lot of options.

Sean

 

[Forrest Addy]

Whatever the conversions may have done using single ratio the point remains: if you desire to maximize motor HP you need the keep the original motor RPM up near the designed frequency.

It's common in CNC machine tool spindle drives to reduce the number of available ratios to one and the overpower the machine as much as five times to secure usable lower speed spindle HP.

If a machine owner expects to drive a J head BP 1 to 1 (no belt speeds) to origanl spindle torque at 660 RPM (the lowest stock belt speed) he needs a 5 or maybe better 7 1/2 HP motor.

Don't get me wrong, I'm all in favor of performance enhancements like a 1:1 ratio and a highly flexible 5 HP all electronic drive. I'd have them on my Bridgepoert in a heartbeat if it wasn't for the cost. I gotta re-stock carbide inserts soon and they're $70 a box. It that's a strain how can I afford a very nice BP spindle up-grade. Inevitably all my home machine shop suggestions are imprinted with thrift.

If the original 2 HP motor and step V belt drive is replaced with 3 HP VFD/motor package is added, you get 70% spindle torque at the lower end of the available range. I frequently run a 5" face mill and that 70% is important to me.

The usual inquiry made to me has to do with adding a VFD to an existing BP J head step drive as an expedient in lieu of a phase converter - spending a few extra bucks to gain superior performance and operational flexibility. My usual response is to do it using a 2 HP single phase rated VFD while retaining the original 2 HP motor and step drive. I (nearly) always caution them to expect maximum spindle performance only if they use the step pulleys (or vari-drive of so equipped) to advantage.

If the inquirer can afford the $1000 plus to power the machine with a 5 HP motor and VFD belted with a single 1:1 ratio, that's all to the good. Unfortunately $1000 to make the conversion is a lot for the average old fart home shop machinist unless a bargain is found.

There's another point a 5 HP TEFC C faced motor weighs about 30 to 50 lb more than the stock 2 HP motor. The little frail worm drive that tilts the head sideways is barely up to the task tilting of the head with a stock motor. Add 35 lb, a higher CG, and a ham hand at the tilt mechanism and it's possible to shear the only two bolts that hold the gear in place.

Regardless, the original question had to do with a Deckel mill not a Bridgport - or is that sly Sean trying to stir up my sensitivities hoping to provoke outrageous political statements?

 

[Sean S]

No no.. not tryin' to be sly...
I just read the part you said about keeping any pulley or gear setups and it made me wonder about some conversions I'd seen (and had considered buying). I couldn't resist to ask an actual "OnT" question

However, I have been wondering what HP motor/VFD combination could be used to power your typical black helo? They keep landing in my backyard and I figure eventually they'll forget and leave one here.

Nice info Forrest, thanks for posting. I learned something today.

Sean

 

[Forrest Addy]

Stoke up on my famous "Sleep on the Couch" chili and the SWAT team will never get close enough to put the cuffs on you.

Scratchy voice on the bullhorn: "In the green fog!! You with the CD!! Put the CD on the ground and back away from it!!"

 

[R Nelson]

I have to convert a FP1. Here's what I'm thinking. The 2 speed motor on my FP1 is rated at 1.1kw (1.47hp) @710 RPM and 1.4kw (1.88hp) @ 1430 RPM. Assuming you want to drive a 3 phase motor from a single phase VFD (for reasons outlined in the previous posts) and deliver the same hp at the two rated RPM's so the feed/speed/# of strokes/etc charts for the machine are calibrated. The ideal 3 phase motor would be:
motor rated 1750RPM @ 60 Hz with VFD set to ~50Hz
high speed : (1.88)(1750)/1430=2.3HP
low speed : (1.47)(1750)/710=3.6HP

so if you pick a 3HP motor you are only going to deliver 1.2HP at the lower speed and you will deliver 2.45HP at the high speed.

another option might be to buy a 2HP motor that runs at ~1150RPM and overdrive it by ~25% for the high speed so you get: high speed= 2HP and low speed = 1.23 HP. (about the same performance with a smaller motor.)

I think I'll go with the 3 horse motor because it is easier to find surplus. As a side note, I have been told not to exceed the max spindle speeds too much on a FP1 because of the plain bearings used in the spindles.

--Bob

 

[Jackson Sowell]

Thanks for the replies. I see that the packages offered by dealers electric are both rated 1800 rpm. They are pretty close in price. Do you think that it would be wise to go with the 3hp?
In reply to Sean, I do have a small lathe, so I hope adapting a different motor won't be beyond my capacities (machine and me) Haven't accurately measured the pulley, but don't think I have enough swing to turn a replacement. If necessary, I'd expect that a suitable replacement pulley may be available thru Grainger, or maybe something a little easier to adapt.
Haven't had time to get down to the nitty-gritty yet. When the time comes, will try to find a digital camera to borrow for picture documentation.
Thanks again, everyone,
Jack
P.S. Suggestions of sources for parts/accessories, anyone?

 

[Sean S]

Hi Jack,
Well, as far as the 3hp motor.... Hmmm....
I find the 2HP motor to be plenty powerful for the machine. Even my late model (86) FP -1 carries a 2hp. I only brought it up as I have seen 3hp motors done with a few VFD upgrades on Bridgeports, however, they are also removing the vari-speed pullies when doing so (which you will not be).
Although I personally might attempt throwing 3hp on one of mine if I were at your junction (just to have a "hotrodded" machine, I suppose it's possible that you could get yourself into trouble this way too if you overpower the geartrain. Don't have a perfect answer...sorry.

For the pulley, from the little that I've looked at them, it should just be a bushing, or a matter of boring out the id...depending on how big the motor shaft is. Doesn't seem like it should be too difficult.

Sean

 

[Brian]

I'm not an expert on VFD's but I do know that they supply full hp for a fairly wide range of original rated motor rpm. The one's that I have are rated to supply constant hp and torque from 50% to 100% of rated motor rpm. Above the rated motor rpm there is a drop in hp and torque, but below rated rpm they can control the amount of amperage and voltage going into the motor to maintain a constant rpm based on the load applied. I can look up more specifics in the manuals if needed.

Brian

 

[R Nelson]

HP = Torque * RPM
A VFD provides constant torque (within limits) when operated below the motors rated RPM (so the HP is always dropping as you reduce the RPM's on the motor). When you run the motor above it's rated RPM the VFD provides constant HP (so the torque is always dropping when you increase the RPMs). Converting a FP1 is a bit more confusing because of the 2-speed motor which uses it's extra windings to keep the torque up at the lower speed as opposed to pulleys/etc. To match the original HP specs in low speed mode you will have to oversize the motor you choose. A 3HP motor/VFD combination will be about right because you will have about 1.5HP in low speed (where you need it) which matches your original motor. Sean is right that in high speed mode you will be a bit supercharged at 3HP. Buy a 3HP motor/VFD combination and never look back!

 

[avk]

I have just installed a FP1 in my shop with a simular problem. If you have the Deckel "box" for the motor control I would strongly suggest that you try to use it. First to get 220 1ph to 3ph get a rotary converter, this will get the 3ph power you need. Next get an Acme 220 to 440 3ph transformer to boost the voltage. That Siemans motor that came with the Deckel is a great robust motor and the box can switch speeds. The final outcome of the whole process is that the full output of the motor is reduced but you still should get 85% of rated power. 3ph motors are so much smoother running than single phase ones.
Alan

 

[noahjlb]

Don't put it off. Get a rotary drum 3 phase converter now, not later. If you have one three phase machine, you will end up with more and soon. You don't need the VFD to get variable drive since that is already built into the Deckel. VFDs run about $500 or $600 for the decent ones and I bought my 5hp. rotary drum convertor for $500 brand new on ebay. If you want to go with infinite variable frequency drive, it's really better to get a DC motor and drive controller than the VFD and AC motor. According to the engineers at Baldor motors, for any shop machine 3hp or under, it is better to go with DC motor and drive controller. Above 3hp. AC motors and VFDs may be better. However, remember DC speed conrollers last forever and VFDs die after a few years of use (and there goes the $600). Also the torque curve at low speeds is better in the DC system than in the AC VFD system. If you drop below a spindle speed of 200 rpm in the AC sysem you will lose a lot of torque. This is one area i have some experience. I have used DC motors and controllers in the past with success. Finally, I don't know for sure but i would bet that the 3 phase system in a VFD is a static phase convertor and unlike the rotary drum, you are going to lose 1/3 of your HP rating of your motor.

 

[Brian]

Noah,

Re: loosing 1/3 of your hp with a VFD. The VFD's convert AC to DC then back to AC into true three phase, there is no power loss whatsoever. They are light years ahead of the old static converters that do what you are saying. Properly sized to the motor requirements and they are very economical to run and I haven't heard too many problems with longevity, unlike every single rotary phase converter I've ever seen that has been rebuilt for the umpteenth time. No associated noise, heat gain in the shop and wasted electrical draw with an idler motor setting there spinning. Just my 2 cents.

Brian

 

[[email protected]]

I had my 380 volt motor rewound by a motor shop in South Carolina. They do well by UPS and have a one week turnaround. It cost $400 and it runs just fine. The three phase converter I built myself (it's really not rocket science you know) for $15 the motor and $25 the start and run capacitors. You might want to reference www.metalwebnews.com/howto/ph-conv/ph-conv.html

Bill Bonta

 

[Jim Williams]

I have a Harrison 10X20 toolroom lathe with a 3hp 240V three phase motor. I ran it for years
with a static converter. When I got the
Deckel GK-21 pantograph, it had a 460V, 3phase
motor. After evaluating a motor change or VFD
I decided to stick with the converter. A friend gave me a 3hp 3phase motor which I drive
with the converter. Output voltage from each
leg of the motor is transformed to the desired
460V, and the original Deckel motor does fine.
The Harrison lathe is operated on the un-
transformed 220 volt converter output and has
a lot more power than just on the static unit.
The three wave outputs are a little distorted
on a scope, but suprisingly usable.
Jim