View Full Version : Simple VFD'S?

07-18-2003, 11:19 PM
I like the vfd's that are found on machine tools,nice and straight foward,I have been shopping around for one for awhile and all I can find are the ones designed for the process industry,I don't need acc-decl.ramping.overspeed or any of that other crap,just a on/off,a potknob,and a tach.any suggestions as where to find such an animal?

Forrest Addy
07-18-2003, 11:55 PM
Most VFD have all that parameter stuff for a reason - system flexibility. You set the the parameters once and forever more forget them. You can seldom find a VFD without these features and the price for the "simple" VFD is likely to be more because it's an exception.

Don't let those fancy features intimidate you. Once you get a chance to monkey around with them they aint too bad.

07-19-2003, 11:57 AM
I'm not intimidated at all,I simply don,t need them because compexity is a sham,the more complex the system,the smaller the malfunction required for a failure.
I think we are paying to much for too little anyway,the damn things probibly cost all of $20 to make.The parameters avalible I can see the need for in the process industry,but not the machine shop.

Forrest Addy
07-19-2003, 02:43 PM
Well, are you making too much of the issue? Maybe your best protest is to not own one.

As for cost, direct manufactured costs for complex products like VFD's are variable but 1/3 the selling cost is probably close. Besides a few mark-ups there's advertizing, shipping and packaging, ongoing technogical development, and profit. It's just how the system works.

The manufactured cost (materials and labor) of a $50,000 luxury car is about $6500. Take it from there.

As for reliability of complex electronics, VFD's do fail (doesn't everything sooner or later) but they are reliable even for industrial electronics. I have 7 VFd's in my shop and never (know on wood) had a problem.

[This message has been edited by Forrest Addy (edited 07-19-2003).]

07-19-2003, 03:48 PM

Go to www.automationdirect.com (http://www.automationdirect.com) They sell ac drives that are probably what you are looking for. ~$300-400. You could interface w/ a user pendant or your computer (added flexibility). You could also look at a regular electromech relay for $20.


07-19-2003, 06:44 PM
It's all programming in the microchip, anyway. I doubt there would be any fewer parts in a "simple" VFD than in one with a lot of features...just fewer lines of control code.

Take a look at the prices for VFDs, from a outfit like Grainger. Then the $200 cost from a place like Automation Direct or Dealer's Electric will seem really cheap.

07-20-2003, 11:47 AM
Forrest, that $6500 seems low.

GM makes about $750 per vehicle it sells, before warranty costs, I assume. The dealer marks are not that high on GM, or Honda etc.

So I would suspect the manufacturing cost out the door with all burden and so forth is higher than $6500. It is for an S10, why not for a bimmer?

I do know that you used to be able to get a Benz from say Brazil, for a *lot* less than in the US. So probably for the luxury cars there is more dealer mark to take care of all the "customer perks" that seem to go along with the car.

As far as VFDs, 1/3 the LIST price is about right for most electronics. The actual or "STREET" price depends on the mark the dealer will accept.

A "simple" VFD would not be much less expensive because the power parts are what costs.

The features are nearly all in the programming, and are "free" other than accounting for development cost recovery.

07-20-2003, 12:57 PM
I do have a gs-1 from automation direct and it works good, the price doesn't even bother me,its all the extras,I don't need to comunicate with my computer,I don't need to change parameters,what I do need is a real tach,constanly thinking about % instead of rpm is a pita,I suppose somewhere in the catalog they have an add on tach for more money,but for now I am going to wait until something better comes along.

07-20-2003, 01:49 PM
Integrating a tach into the VFD is a problem, because you have pulley and belt ratios to contend with. My TECO VFD can deisplay in "tach" mode, and I could if desired (I think) put in a suitable correction factor for a particular belt/pulley combination...but I sometimes change the pulleys, if I want a really low speed, or a really fast speed, so then I'd have to reprogram the VFD to make the tach display come out correctly.

I think the only sane way to do it is to measure the the speed of the spindle, which is what you really care about, anyway. And that's outside the scope of a VFD.

Red Lion Controls (see the Digi-Key catalog, for instance) sells a tachometer module for about $50 that seems as though it ought to make a good basis for a machine tachometer. One would have to set up some kind of pulse generator on the spindle, but that shouldn't be too hard.

[This message has been edited by SGW (edited 07-20-2003).]

07-20-2003, 03:55 PM
Hello wierdscience,

After looking at the GS1 manual, that i downloaded from their website, the drive could display RPMS (calculated which is close enough). Not clowning on you, but it helps to check the manual or call their tech help from time to time. Most of these AC drives have this feature if my memory serves me. Also you could purchase a remote control connection for about ~$50 to tie into the drive.
For the record not connected to automationdirect or get any direct benefit from them.

07-21-2003, 02:16 AM

RTFI - "read the...instructions"

My Intelligent Mitsubishi VFD can display calculated rpm (based on programmed motor specs), or a process number, or %, or actual Frequency. If and external tach sensor is implemented it can feed the ttl circuitry for accurate CNC control of the rpms.

The intelligent controllers offer so much more in utility and longer motor life than the old units that you would hard pressed to find a "simple" unit these days as they are false economy.

07-21-2003, 08:58 PM
Oh!And like you guys read instructions http://bbs.homeshopmachinist.net//biggrin.gif

07-21-2003, 09:03 PM
Oh,forgot to mention,the next one I was going to purchase was to replace the vs belt on one of my mills,the belt ratio is 1:1,and the gear ratio is 2:1 so its not a problem.

07-22-2003, 05:26 AM
<font face="Verdana, Arial" size="2">Originally posted by wierdscience:
Oh!And like you guys read instructions http://bbs.homeshopmachinist.net//biggrin.gif</font>

After performing an enormous faux pas during a physic lab I learned the hard way to RTFI. YOu should be proud of me, I turned a totally screwed up experiment into a "9" (9 out of 9 for marks) by analysing what went wrong - Uncle Dave got a big gold brownie star that day, I can tells ya! Its called learning from your mistakes.

I also confess to having the attention span of a Rotweiller in a butcher shop when it comes to instructions and just "skim" the details to get to the important stuff... http://bbs.homeshopmachinist.net//eek.gif

07-22-2003, 11:08 PM
Well,I only keep them for reference,just incase theres flames http://bbs.homeshopmachinist.net//biggrin.gif
Oh,forgot to mention,good to have you back!

07-22-2003, 11:19 PM
OSO.. Last new vehicle I bought was in 99... A ford ranger, made with mazda parts, cost me 15,000 cash.

GET THIS&gt;.... Georgia charged me taxes on it, before rebate, before dickering discount, before waving cash and leaving discount, of $720 state tax on full amount of sticker, for living in georgia and buying a new truck.

According to you, georgia made as much as ford, with no investment. gee, I want to go into business like that. no investment, just income.

07-23-2003, 01:27 AM
IBEW: nice racket, isn't it. Now, if they wouldn't waste the money, I would not mind as much. Government costs SOMETHING, and so I will pay a reasonable amount, but waste it and I get angry.

GM lost money on mine, new rear end bearings, new rotors, new ignition lock ($500 with "security" features), and a couple other things on the 2000 S10. And to start with, it cost less new than a used one (commercial, but not fleet white).

07-23-2003, 10:14 PM
Local GM dealer told me that they don't make squat selling cars,they make it in the shop.
My grandad worked for Ford and then Chrysler,He told me that a Ford Falcon cost Ford $719.00 on the lot,get this the single biggest cost on the car was,get ready-the cost of the transportation to the dealer! http://bbs.homeshopmachinist.net//biggrin.gif Says alot for mass production.

As for the assorted tax thieves,the system I would like to see is a sales tax on new mass produced consumer goods,no tax on food or drugs and no tax on used merchandise.Leave small business alone(less than $2million a year gross)they will employ more people than industry in the future anyway,don't tax a person on money when they make it ,tax them when they spend it.The system is already inplace to collect it anyway,do away with the IRS and that moutain load of paper and headache we all share,cut out the payroll tax completely,give the worker all of their money and let them spend it as they choose.
Federal taxes are a bad deal anyway you slice it,I am proud to know that even though I don't live in Boston , I did get to help pay for the "big dig"yet the road in front of my house floods every time it rains:!
Now what were we talking about?Oh,I give up http://bbs.homeshopmachinist.net//biggrin.gif

steve schaeffer
07-24-2003, 02:49 PM
i just installed a vfd on my lathe, and i found it very nice to have a smooth s curve acceleration ramp, and an acute linear deceleration ramp with d.c. braking at the end. it took me all of 30 minutes to go through and set the parameter that i needed, and address the input terminals that were wired to my control buttons. you are right when you say there are a lot of parameters that you dont need, but that is irrelevant. no im not using pid control., but thats ok that its there. as far as cost, i am using a small hitachi unit that i got from polyspede inc., and the nice thing is that it is an inverter and creates the third phase that i needed for my lathes motor. i spent three hundred on the drive, but because i did not have to buy a phase converter, i like to think i paid 150.oo for the drive, it doesnt get any cheaper than that for all of the nice things i have it doing for me!