Why You Should Include a Drive in Your Pumping Application

Pumps are heavily used applications in all industries and can be a large portion of a plant’s energy bill making it important that pumps run smoothly and efficiently. In this episode, host Mike Murphy is joined by senior business development manager for Industrial and Municipal Water and Waste Water, Larry Stanley to discuss variable speed drives in the water wastewater industry. Larry explains the benefits of a variable frequency drive (VFD), how motors can benefit from them, and the various controlling methods used in a typical pumping application.

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Transcript

Mike Murphy: 0:09

Welcome to the ABB solutions Podcast, where we address challenges faced in our industry and solutions to overcome them. I'm your host, Mike Murphy, speaking to you from Greenville, South Carolina. Today we have Larry Stanley, senior development engineer with ABB Drives. Larry has 37 years working with VFDs and soft starts in many industrial, municipal and commercial applications. Nine of those years have been with ABB. Welcome, Larry. Hey, Thanks, Mike. I really appreciate being here today. We appreciate you sitting in on this podcast. Okay, our topic today is Variable Speed Drives in the Water, Wastewater Industry. Pumps, as you all well know, are heavily used application in all industries, and can be a large portion of a plant's energy bill. So it's critical that pumps run smoothly and efficiently. To start, Larry, can you go over some of the controlling methods we might see in a typical pumping application?

Larry Stanley: 1:00

Oh, absolutely. You know, I think where I would start would be the most basic, and that's just a plain old starter, which is a contactor with an overload. Now you can think of this starter as like a great big light switch, either the lights are on or the lights are off. And that's it. Well, the starter is much the same thing only it's much, much bigger, we have an air gap between the AC mains and the motor when the starter is off and then when the starter is closed, then we have the motor connector connected directly to the AC mains. Now, what makes this a really cool device, is it simple. It's just a contact, you got a set of contacts and you got a coil. You energize the coil, the contactor closes. You de-energize the coil, the contactor opens. So it's a very simplistic device. It doesn't take up a tremendous amount of room. It's easy to troubleshoot, now. But the decrement is, is when we line start a motor, we're putting the full voltage and full frequency on that motor. And what that will cause in a pumping application is something called a water hammer. When I full voltage start that motor, I'm going to try to bring that motor up to speed as fast as I possibly can. Now that's going to try to displace the air that's in the pipe was whatever fluid or whatever medium, we're moving through that piece of pipe. And that's going to create a water hammer effect when I'm accelerating the pump up. Water hammer can be very destructive. And one of the issues we face in the municipal industry today is a aging infrastructure. So we want to start these motors as easily as we can, so that we don't create this water hammer. Now on the other side of that starter is when we stop it. We can get water hammer when we stop it too, because we might have falling water. But anytime that we're pulling that medium back out of the pipe, or filling the pipe with air. And now, we've got water hammer and when we're decelerating or stopping that pump. And it's just as destructive as when we're starting it. So the good thing about a starter, they're pretty simple. They don't take up a lot of room, they're easy to troubleshoot, The bad thing is and probably maybe not the best starting method for a pump in a municipal application, just because it could drive some damage. Okay, well then, you know, from a starter, I would go over to what we call a soft start. Guys my age, the older, the older generation out there, they'll remember we used to have a lot of electromechanical soft starts. My favorite one was an R-vat, a reduced voltage auto transformer starter, that used an auto transformer again, you had two legs going to the motor. And then we would use a contactor to short that auto transformer out. It was a it was easy. It was simplistic. Okay, wasn't bad to troubleshoot at all pretty easy to start up even. They were expensive. They were heavy. And they would take up a pretty good little piece of room. So back in the mid probably 80's, I think I would say the mid 80's, anyway, we started seeing soft starts, a lot of people might say SSR VS, Solid State Reduced Voltage starters, they started coming into vogue. Now a soft starts really cool because it's simplistic. You have three sets of back to back SCRs, and we use these SCRs to control the voltage that's being applied to the motor. Now what makes a soft start is if I can control that voltage going after that motor, I can control how much torque the motor's going to produce. And if I control the torque that the motor can produce, then I can control the amount of current it's being consumed, at that point. And that's how it becomes a soft start. Soft starts are, used to be the head a great price point compared to a variable frequency drive. They're smaller than a variable frequency drive sometimes. They're more expensive than a starter, but less expensive than a drive. Okay, those are those are the really good things about them. If I look at the other side of it, the bad thing and and maybe that's not a really good thing to say. The thing that I, that I don't like about a soft start is that you can only get about 92% conduction out of that SCR. And realistically, what that means is we're going to have a loss in that, in that soft start, and it's going to generate heat. And it can be enough heat that you know, we have to do something about it. So typically, what you do is you put a shorting contactor. That is we have a contactor that's in parallel with the SCRs, and we'll bring the motor up to speed or the soft start will come up, we'll get the speed, and then we'll close that contactor and we'll put the motor across the AC mains. So that's kind of how soft start works. And, and in some applications, they're they're a really good solution. This places I don't see him as a

great solution: 6:03

self starts and generators don't always get along really well. So you always want to talk to your application engineer, when you're applying a soft start into a pump application, where we're going to have a generator. In another atmosphere, we need to look at, does this soft start give you the ability to control the torque in that motor. Because if you don't, if you don't control the torque, you're not really going to control the water hammer. So that's something else that I think about with the with a soft start. Going way back, if we were just looking at speed control, we had a mechanical mains, and that was called an old Reeves drive. They had a handle on the side of it and you crank it one way the motor would speed up, crank it back the other way the motor would slow down, purely mechanical speed control, okay, didn't offer you any benefits of phase protection or single phase protection or conversion, no energy savings probably used a little more energy, but a lot of people had them, and that was the technology. Then, you know as as a kid coming up in the industry, in the 80's, we started seeing the variable frequency drive come on to the scene. More and more stronger, stronger. Early on, one of the issues with the drive was they were big, they were real big. Think of refrigerator big, even for a smaller one. They were pricey. And in some applications, or some instances, those early drives may not have been considered the most reliable piece of equipment in the world. And because of that, our engineers had to specify some bypass mains. And that would typically be a full voltage starter, so you would have a drive with a full voltage starter in the same enclosure. Well, the drive does a fabulous job bringing the motor up and down in speed, because we're controlling the voltage and the frequency at the same time. And when it worked, it worked flawlessly. But if it failed, then we'd have to go back to the starter, and then we'd have to do this probably use some valves to help control and try to make sure that we weren't getting terrible water hammer in a system. Now, fortunately, as the years have gone by, and the drives the size of the drives have come down tremendously. I mean, just there's no comparison. The cost of the drives, if you look horsepower to horsepower, and everything, the cost of the drives, it's more economical. So now our engineers can specify or build a system where we have a spare drive or like a plus one design, where we'll have a motor and a drive setting there in case one of them goes down. And we don't have to have this bypass. Years ago when I was a kid that really wasn't practical because you really couldn't have another giganto drive setting there in a in a very expensive bypass arrangement and everything, so the drives that we have today, the technology has allowed us to put a piece of very dependable equipment out into the field that does a remarkable job in the pumping industry.

Mike Murphy: 9:14

So Larry, what are some of the benefits then in the application? What are some of the benefits of using a VFD?

Larry Stanley: 9:20

You know, Mike, my opinion here is gonna be different than everybody else's, you know? Because I look at these solutions based on being a troubleshooter. I started my career with variable frequency drives being the guy that had to go out and fix them. I was the guy that you called if something was broke, so my opinion might be a little bit different than some of the other people's opinions. But for me, I don't want to tell you my opinion, the number one benefit of utilizing a drive is the ability to control control that soft starting and self stopping all the time. It It doesn't matter whether I'm a decelerating or decelerating, I'm controlling the voltage and the frequency at the exact same time. It's a ratio, it's called volts to hertz ratio. Okay. And today we have some new algorithms and they're not new anymore. They've been around for a long time, that your algorithm algorithms where we can actually control the amount of power or going out to that motor so that we don't ever have to worry about water hammer. The reason I look at this is I know that one of the main issues in the municipal industry is an aging infrastructure issue. We've got stuff that's been out there, the, say, 50 years is, is easy, longer than 50 years, sometimes we have valves that people haven't seen for a while, or a pump. And we we want to be careful how we're starting those, we don't want to expose this aged equipment to this water hammer condition. Well, with a variable frequency draft, that's never an issue, not zero. And it's all because we control the voltage, which controls the tour. And we can control the frequency, which controls the speed, we do that in a combination so that as we're ramping this drive up, we never have an inrush current, never none zero, the current comes up smooth sail. And when we're bringing it down in speed, it comes down smooth as silk. That's what makes a drive the perfect starter in a pumping application. In my opinion, that's what I like to look at, because it doesn't break stuff. Okay. Now, from there, we have to look, it's not just municipal industries, it's got to be utilizing the drive, we have all drops and a lot of irritation applications. And sometimes the pipe for this irrigate in these irrigation applications, that piping might be miles long. And we want to be able to softly fill that pipe, we don't want to put a huge water column, we don't want to be pushing up a larger water column in through that pipe. So in the drive itself, we have something called South pipe field. That's a really neat method of of basically filling this pipe, making sure that the pipe is loaded with water in then we can turn the PR loop on and control. And we never have to worry about having an issue balancing the BI loop when we're bringing it up on startup and everything or whether we're starting the motor from scratch. So the soft pipe feel is a really neat thing. If I'm looking at wastewater, one of the issues that we can have in wastewater is a fouling pump. And brother, let me tell you, the thing, nobody wants to have to go out and clear one of these pumps. First off, you've got to pull the pump that's expensive, it can be downtime, you've got to take a crew, you've got to dispose the waste, you have to make sure your guys are operating in a sanitary atmosphere, there's a lot of negative stuff about pulling a wastewater treatment pop, I don't want to have to do it, I don't think you do either. So in the draft today, we have the capacity to watch that pump that allegedly. And we can predict when that pump is becoming fouled by watching the speed, the torque and the current. And we can take the drive and we can say Hey, man, this pumps getting found you won't do anything about it. And we can just alarm and not do anything. Or we can say Hey, man, you want me to clean this part for you. And I can utilize my variable frequency drive, to control the motor to a cell rate and decelerate this motor in a fashion that will clear the fouling in that pump. We clear we put it into a run command. And we check it. And we can do that as many times as you want. You're in control of that. You set it up, you set the pattern up to clear to clear the bow exactly like you want it to work. It works like a champ. It's a great light inside the inside the drives for or for the municipal end, especially in the wastewater side of it for waste or fresh. We can do things like a flow calculator. A lot of times we just need to know Do we have flow? What kind of flow do we have? Now the draft does have a flow calculator in it. It's probably around 15% accurate you think at 15%? Well, you know what my realistically, as long as I know that I've got something there. If I need to be really, really critically accurate, then I'll do something else. A lot of times though, I just need to know I've got flow. It works great for that. Really good. So that's one of the things I look at inside the drive. Even thought talking about freshwater and I'm talking about submersible pump, I'll look at the thrust bearings in that pump. And you know, you got to have some water under that thrust bearing so you don't foul it. So inside the drive, when we get ready to started up, we tell it's going to be a pump. In the drive, we'll just ask it says, Hey, man, what kind of pump Are you fresh water wastewater, you say I'm fresh water pump man. And the drive will actually walk you through setting it up, so that we can do Quick, quick ramps, so that we can quickly bring that pump up to 30 hertz, maybe in two seconds, maybe in three seconds, so that we protect the thrust bearing. And then we just put a program in the balance of our ramp, palms up and down. It works like a champ. It's great, it's easy. Our users don't have any trouble setting it up. And it makes sense to them. It makes sense because we defined the pump as a wastewater pump, or a freshwater pump. And we do this on the keypad. Basically, in a spoken language, just like I'm talking to you right now, my day, it might not say Hey, man, I probably wouldn't get down from West Virginia. But you know what, it does say very clearly, what kind of pump Are you in? What do you want to do? Those are the neat things when I start looking at it from that side. Now, once that drive is put in place, we got to think about the longevity. And that's going to be driven by the ability to monitor the system. Today's drives are remarkable in what we can pull back or other I can look at, I can look at the current in all three phases that motor all at the same time. If I wanted to, I could take a laptop with a piece of free software, no cost free, just download it to your laptop connected up with Ethernet cable. And I can sit there and I can watch all three motor leads. Might some people might say I don't care about that. What do you do? Sure you do. If I can watch that current, almost three motor leads, when I'm doing a start up, I can look university that current bouncing, maybe I plot, motor current against tour, and I'll watch that pump come up to speed. And if I see a pump come up speed, nice and smooth load torque ripples in it. I know this is going to be a good long life path. I'm not gonna have any trouble with this thing. Maybe I look at it, and I see some ripples occurring in the port. Then I got to go back and figure out what mechanically is causing this problem. electrically. The other thing I can do is about Look at that. And I know that's a make it easy for me. Since I'm mapping the number one language will say 100 amps. Let's say we've got a motor that sitting there and it's 100 amp motor. And I bring this drive all the way up to full speed to 60 hertz, that I'm not drawing but 85 amps set a problem? Well, it depends. It's not a pot problem for the motor. But maybe we don't have the flow that we should have. Because the current in that motor is going to be reflected is reflected as a reflection I suppose from the amount of work that the motors doing. So if I'm down 15% on my current, I could be down 15% on the load. Okay, or maybe 7% I'm alone, so it can help you understand what is happening mechanically in that system. By watching. I'm monitoring the pump, electrically. Really cool thing. Yeah. Okay, that's impressive.

Mike Murphy: 18:41

But you talked about viewing some of the current regulations amp draw, what are the ways can a motor benefit from using a VFD

Larry Stanley: 18:48

I would compare that against let's say a full voltage starter. When we use a full voltage starter to bring the motor up, the motor is going to be exposed to everything that's happening out on the AC mains. Because the motors tied directly to the AC mains. If I get a squirrel on the line, and I get some type of voltage spike, it's going to go to the motor. If I have a low voltage condition, if I have an outage, if I have a single phase, everything that happens out on the AC main side, the motor is going to absorb it because the motors tied directly to the AC mains. The other thing when I use a starter and full voltage starting the motor, I'm putting for voltage and for frequency. Okay, so what are at that point the motors will be voting start. So I'm going to draw a very high amount of current coming to bring that motor up to speed I excite the motor, I'm gonna have to break the motor away and then I'm gonna have to accelerate the motor. That's where all that inrush current comes from. And that's what we get when we take a starter and we tie the motor directly to the AC mains. Now when I will Look at it with a variable frequency drive, the drive literally isolates the motor from the AC mains, as long as you're utilizing a variable frequency drive that has a true DC bus, if I have a diode front end, if I have a set of bank capacitors, bus capacitors, and then I have my IGBT section, I can utilize that variable frequency drive to isolate the motor from the mains. That gives you several benefits a drive with a DC bus in it, I can go single phase, if I've sad state drive correctly, I can run forever. without incident on a single phase condition. I actually have pump stations, where we have single phase power, and three phase generators. And as long as as long as we stage it correctly, we bring it in correctly, there's no issue whatsoever, I can either run it off the mains on single phase, or I can run it off the generator on three phase, not the least uncommon. That's the benefit. If I look at the fact that I'm no longer ever going to voltage start this motor, I'm going to I'm going to have voltage and frequency following each other. And I'm gonna bring that motor up to speed very gently, okay, and I'm never gonna have any interest current, that's a great benefit. If I've got existing harmonics, let's say I've got some other drops out there are a bunch of other jobs out there. And I tie that motor to the AC mains or the starter. And oh by the way, this is true for a soft start too, because lots of times the soft starts if I have a shortening nonfactor in it, but let's say I've got existing harmonics on AC mains, that motor can import those harmonics into that motor, and it will shorten the life of the motor. If I had my variable frequency drive there, once again, that drive is going to isolate the motor from the AC mains. So we get the benefit of may never ramp the motor up and down with no inrush currents, we get the benefit of protecting the motor in case we have an unbalanced voltage. In case we have a low voltage. If we have a single phase condition, we protect against all that. So there's a lot of benefits for the motor itself all the way down into the mechanical side. ABB owns bout or and I don't know that I really thought about this a whole lot before I got the dog with some bad boyfriends. But if you land start a motor, and you watch the landings inside that motor and bound or actually did this force, they had a small camera, and they recorded exactly what happens to the windings inside the motor. When you land start that motor, these windings are literally pulled and burst. It's it's dramatic, what goes on inside a motor mechanically in the winding when that motor starting up. If you start the motor once a day, twice a day, four times today, it's kind of like who cares. In pumping applications, you might be starting this motor up and you might be starting and stopping this motor, I don't know 15 times a day, you wouldn't be unusual thing. In some applications, it might be more than that. So every time you start and stop that motor across the line, you would be exposing that winding to a mechanical shear almost inside of it. When you start the motor up with a variable frequency drive, nothing happens. It's smooth a seal.

Mike Murphy: 23:33

earlier on. You talked a lot about aging infrastructure. I know that topic of water hammering came up that sounds like pretty destructive occurrences in the application. So we know ABB is huge in running equipment safely. Can you go over some areas where ABB implements an aspect of safety in their jobs?

Larry Stanley: 23:53

I'd like to talk about two things, Mike if it's okay, I'll talk about the draft but I'll talk about ABB as well. For me, and it's it's truly a personal note, I really enjoy talking about art clash whenever I go out and see a customer. My father was critically burned in a mining accident in 1967. I was just a little guy at the end. And I've always thought that you know if I can bring anything to a person to you, Mike to a customer to anyone, if I can talk to them a little bit about arc flash and just encourage them to work in a safe environment. It really it really means something to me, it really means something to me that ABB wants me to do that. Let's get back to the drive itself in our industry in the pumping industry. Or let me I guess I should really say the municipal industry for the drive. I'll look at something that we have called Safe torque off inside the drive ma municipal industry. They probably don't even recognize that term. Or they they might they could I don't know for sure what they do recognize is a term called e stop historically when we did he stopped We might have to put contactors in front of the drive. And after the drive to provide electrical isolation, that adds a very big cost contactors aren't cheap, they're not free, they cost a lot of money. But the real trick is they and footprint, you got to put them during contact or somewhere. Now, the technology that we have with our ACS 580 Drive is we have something called Safe torque off. And I can configure that as an E stop circuit for Deadman switch, okay, I can actually put a mushroom switch on the front of the drive enclosure, and I can if I operate that switch, I will literally isolate the output. And this able to draw from being able to output anything very easy to understand, we don't need power contactors. The only footprint that it takes up is the operator that you put on the door, it basically cost you nothing, because it's part of the drive design itself. And the really cool thing is, is it doesn't burn any of your own account. It's got its own input. So we're not gonna use one of our digital inputs to program it and use it for our safe torque off or II stop. So yeah, I ABB does, and it's, I would call it the ability to do an E stop or a safe torque off on the drop without having to add a lot of power contactors anything.

Mike Murphy: 26:25

So we're going to stop here. That's all the time we have. But Larry, thank you so much for speaking with us on variable frequency drives in the water wastewater industry. We hope you come back and talk with us on a future podcast where we'd like to discuss energy savings opportunities with vfds. If you'd like more information on variable frequency drives, or other ABB products, contact your local ABB sales representative. And if you have comments or suggestions for future podcasts, visit us at us dash solutions at ABB comm Larry, thank you everyone listening Thank you and have a great rest your day.