Any reviews on Precision Power Labs motor controllers

[alpercelen]

Have you ever used a AC motor controller by Precision Power Labs? We are looking to buy a controller for a 75kW motor to increase efficiency and wondering about the reputation and quality of Precision Power Labs. What kind of efficiency improvement did you achieve with your controller?

Thanks for replies,

Al

 

[sreid]

From a Precision Power Press Release

Please note: Energy savings results may vary due to mechanical equipment design, motor size and design, equipment run times and local electricity rates.

There have been threads on this subject. The energy savings for most appliciations will be small to nonexistant.

 

[ozmosis]

Alpercelen
I would suggest you read the FAQ: faq237-971
Ok, it's not a Nola device but it appears to be something similar.

 

[LionelHutz]

Sounds like a Nola device to me.

Almost all soft-starter manufacturers offer an energy savings feature. It's just that the major players don't push it because they know it's mostly snake oil. So instead, they concentrate on the usable features.

It's amazing that the PPL starter samples the voltages and currents 20k times a second but only provides a simple open loop voltage acceleration ramp. And they seems to have absolutely no info on what features that unit has besides it's ability to save power.

 

[jraef]

LOL,
Either their art department has taken liberties, or their design leaves a lot to be desired. Their drawing shows triacs, not SCRs.

That's the worst way to do motor controls on 3 phase motors. So to assume the best of them, the engineering dept. did not review the marketing materials, or didn't care about the inaccuracies, or had no say so in making the information accurate, or assumed the customers would not know the difference. In all of the above cases, nothing speaks well of their engineering practices.

There is absolutely nothing new here, this is the same old rehash of existing technology that has been proven over and over to be practically useless in saving any sort of appreciable energy. It technically works, but not anywhere near what they claim. The last example I did worked out to be about a 30 year pay back on the installed cost. Woop-tee-doo.

Granted, there is a viable application in escalators in places like Las Vegas, which has the highest number of escalators per capita of anywhere in the US. That is likely why these people are in Phoenix. But they only save energy on UNUSED escalators, such as those in Las Vegas that may run 24/7 but are only loaded with people only occasionally in very short duration events. If an escalator is carrying people nearly all day long, the savings are practically non-existent.

Bottom line, this version is unlikely any different than any of the other myriad of recent start-ups who are attempting to revitalize an already dead market by using the current mood of energy savings to capitalize on the general ignorance (not meant in a bad way) of people who are too busy with other projects to investigate them fully. None that I know of ever stand up to the scrutiny of real engineers who understrand the principals invalved.

 

[jraef]

I know it sounds like I'm piling on, but this was too important to pass up. This unit appears to be woefully inadequate even as a soft starter. In reading the technical specs, a unit rated for 200A will shut down if current ever exceeds 280A! I have no idea how in the world it would EVER start an AC motor with 140% current. Not only that, but the minimum voltage adjustment on a 480V unit is 300V, or 63%. So the softness of the soft starting is not going to be very soft on lightly loaded motors, yet it is not heavy duty enough to start heavy loads (or light one either by my reckoning). All in all, not a very well thought out design IMHO.

If you want a soft starter, investigate and buy a good quality soft starter, there are plenty available from major manufacturers with good reputations. If you want to save energy, look carefully at where you are really wasting energy and address those situations. Be careful of hype, this product being a prime example in my opinion.

 

[ozmosis]

Maybe it's bypassed on start and once started they bring in the device...

 

[jraef]

Doubtful. If it were bypassed after starting, the "energy saver" would no longer do even the little bit it claims to do.

 

[RocSolid]

I have worked with this type controller extensively before and I have the following comments on the above statements.

1. The voltage reduction of a Nola type controller will work on a large number of escalator applications. Jraefs comment that the escalators need to be minimally loaded is correct, but the reality is that at least half the operating escalators are minimally loaded because they operate in the down direction. When someone gets on a down escalator, the load on the motor is actually reduced, not increased due to the force of gravity acting on the weight of the person. I have personally verified this with kW power measurements. Furthermore, escalators moving up must still be designed for some extreme case like a 200 lb man on every step. While I don't know what the precise design requirements are for escalators, even if they are crowded by personal comfort standards, they are likely still not near the design load of the motor operating them. This makes them a good candidate for Nola type control and energy savings. On real, in service escalator applications a reduction of 25% of the preinstallation kW usage is not uncommon.

2. To achieve any appreciable savings the motor must operate under minimal load compared to its design for an appreciable amount of time. While not every application fits this description, many do. Large fans and blowers almost always have oversized motors by design because the torque required to start them is so much greater than that required to keep them running. Most of these motors are a compromise between starting current and running efficiency and because of that, run at far less than their design load. As a result, they are also good candidates for this type of energy saving technology. Similarly, liquid pumping applications are another one where the motor is typically sized to produce far greater torque than is really required to pump the water continuously.

3. The biggest factor in whether this type of device makes sense for a particular application is probably the amount of usage (total operating time) and the cost of energy. Obviously, if the controller saves 50% of the used energy, but the motor only runs for an hour a day, the dollar savings is not going to be that great. In addition, the cost of energy is a huge determiner on the financial viability of a given application. If energy is expensive, 5% could be worth it, if it is cheap, 50% would be a rip off.

When investigating this type of energy saving controller I would suggest evaluating each application that it would potentially be used on. The controller does work and in the right application it does save considerable energy. Contrary to what some would say, these applications include single and three phase applications up to 350HP or more. I have personally seen the real kW reduction on many different applications operating on customers sites and under normal conditions. While there is some hype in many of the claims made by various companies, the technology works and can be an important part of an overall energy management plan.

 

[jraef]

I would not dispute most of what you say, other than maybe your assertion in item 2 about pumps and fans requiring large amounts of torque to start up. I have never found that to be true, at least not with centrifugal pumps and fans. In fact one of the main reasons why you apply soft starters to centrifugal loads is exactly because they do NOT need all the available torque to start. Motor loading with them is linear to flow, so if you reduce flow, you reduce the load. If someone has oversized a pump and can do the job with less flow than it is capable of, a VFD will out strip any energy savings a Nola controller could provide in a fraction of the time.

But I do agree with you that nobody should enter into buying one of these things without a thorough evaluation of all aspects of the application by someone who truly knows what to look at and for in terms of energy savings. In the light of informed evaluation, the marketing hype becomes transparent.

 

[LionelHutz]

Ya I agree there jraef, most pump applications run their motors very close to rated power. Typically, the only time I have seen a pump motor running a lower load is when the application included a throttling valve and in most of those cases a VFD will quickly put the NOLA controller to shame.

Fan motors usually are also closely sized. With many high inertia fans the motor is sized to the required fan running power and the start just stresses the motor.

I will agree that escalators seem to be the quoted standard application for this though. They can't be run slower so a VFD is out of the question and the NOLA controller can show the most possible energy savings one one compared to almost any other application.

 

[grumpyB412]

Sorry to join the discussion late, but just became aware of this web site and thought I could add some (hopefully) relevant comments.

I work at Precision Power Labs, and created the drawing above. While I kind of like it, I will accept any and all criticism. My intention was to explain the basic operating principle of our controller product as clearly as possible. We do in fact use SCR modules that contain inverse parallel discrete SCRs, and I did draw triacs (jraef is correct). I did this intentionally because functionally a triac and 2 discrete back-to-back SCRs with the gates tied to the same trigger circut will conceptually do the same thing. We do in fact use SCRs because discrete SCRs have better heat dissipation and are more robust in a real circuit. I just did not want to draw the extra gate lines on the figure for the sake of clarity. IMHO, it is a bit heavy handed to condemn our engineering department for such a small thing.

Since I brought up SCRs, the 200A unit uses SCRs rated for 500Arms, 1600V holding (VRRM/VDRM), and short duration (8ms) current withstanding of 1230A. Very adequate for a soft start. If a customer has an application that is starting a very high inerta load - such as a flywheel - we have the option to use larger SCRs on a custom basis. Our customers and even some motor rewind shops tell us that our soft start is one of the best they have seen - true story. Futher, we do use active control on 3 phases. Evidently, there are many soft starters that economize by controlling 2 or even 1 phase.

I also need to eat crow about our web site in general. It is very basic and desperately needs to be updated. For example, the information cited above is not properly listed. In fact, one of the best parts of our product is not even mentioned. That is PC-based software that links a laptop computer to the controller via RS-232 that allows a number of motor control functions such as adjusting soft start, kick start, soft stop, savings optimization, a host of fault detection features, and data logging that dumps 30 days of data to an excel chart.

To clear the air on a couple of small points:
1. I have lived in Phoenix for 22 years so this is where I stated my company. I have only been to Las Vegas a few times.
2. While I learn new things everyday and probably do have much to learn, I am a "real engineer" (Ph.D./EE, 1998) and think I do understand the priciples involved. I also try to make our customers aware of the same.

One final point is important:
We do sell our controllers as energy saving devices. They do other things well (in fact better and less expensively than many single purpose products) but we have chosen to focus on energy saving. The key is properly characterizing the application before we install a controller. We do this as standard procedure along with a discussion with the customer about what they can expect in terms of savings. Further, we generally tell customers that if their proces can tolerate reduced speed/throughput, a VFD may be the way to go. If full-rated rpm is desired, then often our product ends up being the best solution. Have you looked at the price of a VFD for a 300HP motor? No single technology is a priori the "best".

Thank you for the opportunitiy to respond.