vector control on pump

[Andy32821]

Hi Guys,

I have two questions I'm hoping you can help me out with.

Question: 1) Is there any technical reasoning to use a sensorless vector drive on a water pump application that would justify the extra (10% ?) cost?

background of question 1:
I replaced a Square D omegapak installed in 1995 25 hp 480 volt drive on a domestic water pump with a cheap durapulse $1300 sensorless vector drive. I was amazed at the improvements. Pump noise went from a scream to whisper, vibration problems disappeared and control to setpoint improved. (I'm now using the drive's internal PID rather than an an outdated electronic controller). Motor is a 1770 rpm inverter duty that will operate from 800 to 1200 rpm when running.

So I put out a RFQ for 25 hp sensorless vector control VFD to be used on a variable torque application.

One of the vendor's (well liked by my buyer) wrote me to say that the extra money for the vector control gains me nothing when used on a variable torque application and I may want to reconsider my specs.

I admit I spec'd the vector technology because I thought it sounded cool.




Question #2

The quote for a Toshiba drive was $2400. I pay $1300 for a durapulse. I have used the durapulse for several years (in light duty applications) with no problem. Why is the Toshiba an extra thousand dollars? (Is the durapulse junk that is going to die on me in a few years, is the Toshiba built for heavy duty applications, or is the vendor just hoping to get lucky?

Thanks,
Andy

 

[itsmoked]

Q1;

There have been many improvements on VFDs since they hit the market. Newer ones are often much smoother and quieter.

You should not need vector on a pump.

I'm confused by your question. Are you saying you replaced a vector with a scalar and it is now quieter, or the other way around?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ozmosis]

The audible noise may not be simply the change from a basic V/F to a SVC. It could be the switching pattern/speed of the the replaced VFD. However, a good sensorless vector drive should provide better performance and therefore the noise can sometimes be better. It depends on the motor as well-cheap low cost motors often are quite noisy.
Generally a vector drive on a centriugal pump can be overkill but these sometimes have other benefits, it depends on your application and industry. Semiconductor industry want pumps with very high performance and compliance with specific standards that could sometimes mean your VFD needs vector performance.

Read your comment "I admit I spec'd the vector technology because I thought it sounded cool". (smiling now) we spend zillions of $'s developing high specifidation drives, trillions on marketing and hey, we only need a cool name!

2) I don't know a durapulse drive but I know Toshiba as I started my VFD career with them in 1988. They are a good drive and generally very reliable so you do pay for what you get sometimes. Check the features and apples for apples-could be a few oranges in there.

 

[ScumPunk]

Does the Durapulse drive run in sensorless vector by default, or did you go through all of the setting up for it? It could be that by modelling the motor correctly (which may not have been the case on the old VFD) you introduced the improvement in performance. IME most VFDs run in V/Hz by default, by its very nature, a fair amount of work needs to be done to get a SLVC application running properly.
As mentioned previously, the reduction in noise would be more likely caused by a difference in switching frequency/pattern, and the technology has moved on in the past 15-20 years. Even the past 5 years in our case
Cheers,
Mort

 

[jraef]

Durapulse is the brand name for what Automation Direct sells. The problem is, they are not the manufacturer, they are essentially just a distributor of a product brand labeled from the cheapest source they could find, in this case I believe it is Delta (not sure though). So they have nothing to lose if it becomes a boat anchor in a few years, as long as it lasts out the warranty. Their marketing strategy is to appeal to the lowest price shoppers, who generally don't care about things like quality, long term support, reputation etc.

Toshiba and companies like them make substantial investments in people and product support. Most of the advancements in VFD technology come from large companies with R&D budgets who continually look to improve their product performance and application usefulness. The money to do all of that comes from somewhere. Companies such as Automation Direct simply hitch a ride on those advancements and sell them cheaper. Their R&D budget consists of a person somewhere scamming for the next best brand-label deal from another copy cat manufacturer who will sell their knock-off product cheaper than the last one. If that appeals to you, go for it. But don't complain when you end up at the unemployment line because YOUR job was eliminated by a knock-off manufacturer somewhere.

You get what you pay for.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[sreid]

One thing Sensorless will do for you is that you won't need whatever speed control you are now using. The RPM will be whatever you ask for and won't change with loading.

Get a quote directly from Delta Electronics. They do make Brand Labeled VFDs for OEMs which includes some major automation players. The big names charge higher prices because they can but also for the support backup they provide.

Delta's claim to fame is power supplies for cell towers, an application requiring seamless reliability.

 

[LionelHutz]

I believe you are correct. I also believe Automation Direct sells labeled Delta's. And Automation Direct basically is the Wal-Mart of industrial equipment. They are doing well at it though.

Did you set-up the Durapulse to be in vectorless mode because I'm betting it comes in V/Hz mode as the factory default?

The SquareD drive could have been set-up wrong and that was causing the rough running you were seeing.

You usually don't need a vector drive for a pump, especially just in a general purpose pumping application.

Look at the specs of this Durapulse drive and see if it uses spread spectrum carrier or frequency shifting carrier or some other name for the carrier frequency. Some drives use this to spread out the noise from the carrier frequency. Instead of being a single frequency carrier which causes a single tone, it spreads the noise out to sound more like white noise. It's still as loud but it doesn't sound like it. This could be part of the reason the new drive is quieter.

 

[jraef]

... This could be part of the reason the new drive is quieter.

I agree. That, and the fact that a Sq. D Omegapack VFD, even if installed in 1995, was significantly older. Omegapak went away with the Schneider purchase in 1989. So it would have been a darlington based analog drive and therefore incapable of more than probably a 1kHz carrier frequency. While 1kHz is somewhat better for the motor, it is probably the noisiest way to get one spinning. It also would have been very short on features we now consider to be basic necessities; Sq. D was at the end of it's ability to keep up with product advancements right before the Schneider buyout, so even when it was new, it was a woefully inadequate drive. (I know, because I was working for them at the time.)

I also agree that vector control in any format is somewhat pointless in a pump system. In fact it adds a level of complexity that you may not want in terms of needing to be tuned to the motor, which becomes an issue if you ever need to quickly replace the motor for some reason.

The better performance you are noticing is more likely due to the difference between a basic technology that is now over 20 years old in the Omegapack drive versus one in the Durapulse that is maybe only 1 generation back from the best available.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[Andy32821]

Hi Guys,

Looks like I might have accidentally spec'd the right drive after all.
Looking at the Automation Direct catalog any drive over 10 hp goes to the GS3, regardless of the application.

The GS3 has svc but also has a parameter that allows you to choose the application; constant or variable loads. I'm not sure but I suspect setting "variable" bypasses the svc and defaults to whatever control is best for pumps.


This one drive fits all may be the future. It could cut down on inventory.

Thanks for the help everyone.

Andy