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VFD Recommendations.....

VFD Recommendations.....

VFD Recommendations.....

First of all, I'm new to the board.  I've used the site a few times to research questions, but have never used it to post.  My questions is very simple.  What brand of VFD's do you recommend?  I consistantly use VFD's for various applications (conveyors, fans, misc machines, etc..).  Most of the applications are 20 HP and less and use 480 VAC.  Open loop, general purpose VFD's usually fit the bill.  I've experimented with many different brands.  I've had relatively good luck with all of them, however, I seem to have just as much success with cheap ones as expensive ones.  We use a lot of cheap taiwan manufactured Delta (www.deltadrives.com).  We've used a lot of Toshibas, Square D's, ABB's, Allan Bradley's, etc etc.  My inclination is to continue using the Delta's, but I'm affraid of future consequences.  Any opinions you can offer are greatly appreciated.


RE: VFD Recommendations.....

Seems like you've answered your own question.  I've never heard of Delta, but if they are working for you, then I don't see a reason to switch.  We'd have to have a lot more information about your applications and your system to give you a much better answer.  

Drives in this size range are nearly all 6-pulse PWM drives and have become nearly a commodity item.  Many people are purchasing these mounted inside MCCs.  I'm sure there are differences in component quality and the level of conservatism in sizing components, but unless you're unhappy with the drives you're using, I don't see a reason to change.  

Bigger drives are another story.

There is some advantage to using a single manufacturer, since the logic boards are often identical over a wide range of drive ratings.  This can help with spare parts, etc.

RE: VFD Recommendations.....


I have a lot of experience with Delta drives.

We have a lab set-up where we did the pepsi challenge with Delta versus other drives. (The tester is a NEMA 4 cabinet with heaters and a variac to raise the line voltage to over 500 vac to simulate NA utility conditions. Externally it has a bonitron unit for braking, marathon blackmax motors, and opposing drives which have torque limiting to provide  loads. It's a really interesting set-up needless to say.)

We ran these drives at ~150*F at 520 vac for over a month. We ran them loaded with an 5 sec accel and decel time. All the other drives failed, these ones, we couldn't get to trip or fail.

It was a test to see how well they were made. The research that I found, was that Delta is one of the biggest power supply mfg. in Asia. We felt that if they make great power supplies then their drives would be made just as well.

Inexpensive yes, Cheap no.

The problem with most Asian drives is that they are voltage intolerant on the high end. In Japan for instance, the micro-drives are designed for a 400 volt system. When they go to get UL listed, they have to drop there high end to 460 instead of 480 to meet the requirements. They can still be used with great success if the proper line reactor or bucking transformer is used to stay under 460 +/- 10%.

The Delta's don't have this problem.

I'm not a salesman or rep...I have no real brand loyalty per say. Are there drives out there that can do a better job with more bells and whistles, sure. But I happen to agree with dpc. If they work for you, then use them.


RE: VFD Recommendations.....

Thanks for the input guys!  It's nice to have some support on this subject.  Until now, I've been basing my purchases on past experiences with no outside input.  I appreciate your insight.


RE: VFD Recommendations.....

Suggestion: Please, would you elaborate on "but I'm affraid of future consequences". Does it have anything to do with "hatching all eggs in one basket"? Theoretically, there could be a common mode failure in the product (including a price). Practically, it may be very remote.

RE: VFD Recommendations.....

To my mind its always good to source a kind of product from two differnet sources, even if at some time one of the suppliers seems to top all the others. Otherwise you might be in a poor situation if the prefered supplier has quality problems or try to increase the price.

RE: VFD Recommendations.....


I guess by "future consequences" I meant that I was affraid of failures of the VFD's and any possible long term effects on the motors.  


RE: VFD Recommendations.....

I have heard from two different drive suppliers that there are really only 2-3 real mfgs of drives for off the shelf supply. The rest of them private label from these 2-3 mfgs. Can anyone confirm this?

RE: VFD Recommendations.....

I don't know if it is only 2 or 3, but there is certainly a lot of brand labelling going on.  As an example, the Siemens Relcon drive of the early 90s was built by AC Tech and later brand labelled by Schneider and Cutler-Hammer after Siemens dropped the Relcon line.

RE: VFD Recommendations.....

Buzzp and redtrumpet:

There are more than a half-dozen off the top of my head under 10 hp. A lot of companies still insist on making there own. It comes down to "Can we as a company make a drive for less money than we can buy one for."

The easiest way to tell is pull the cover off and look at the boards inside. The private label drive is mostly retooled enclosure, operator interface, and parameter set. Sometimes you get a specialty interface like devicenet added as an option. The boards inside are labeled by the oem just like the accesories (some of them anyway).

Over 10 hp you have some of that going on, but it gets blurry. Over 100 hp is totally a new ballgame.

I can't wait to see what we are like in 10 more years...lol.


RE: VFD Recommendations.....

Suggestion: Visit
and type Drives: Variable Frequency under Product or Service, which will return 74 Companies to choose from.

RE: VFD Recommendations.....

Suggestion to Mkraft (Industrial) May 6, 2002 marked ///\\\
I guess by "future consequences" I meant that I was affraid of failures of the VFD's and any possible long term effects on the motors.
///The failure of a variable frequency drive is embedded in its lifecycle, Mean Time Between Failure, Mean Time To Repair, etc. This may be available from the manufacturer. Considering the number of drives produced and sold, the above figures could be reasonably accurate for your Firm.
When it comes to the VFD motor, that depends on the motor suitability for the VFD. Visit
for "spike-proof" motors, and
for papers addressing various phenomena pertaining to motors and AC motor drives, e.g. length of cable, common mode currents, motor bearings, etc.

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