EECO Asks Why Podcast

072. Idea - What is a Soft Starter and what are the best applications?

February 03, 2021 Electrical Equipment Company Season 3
EECO Asks Why Podcast
072. Idea - What is a Soft Starter and what are the best applications?
EECO Asks Why Podcast
072. Idea - What is a Soft Starter and what are the best applications?
Feb 03, 2021 Season 3
Electrical Equipment Company

In this episode Chase Boehlke gives a great breakdown of what a soft starter is and where they fit best in industrial settings. He walks us through how to properly size the solution as this can be an area that people struggle with. 

He digs deep on applications to help understand when soft starters are not the best solutions.   Finally he reviews when other alternatives should be considered. Chase brings a tremendous amount of knowledge to this topic and we hope you find the information helpful. Thank you Chase for shedding so much light on the exciting topic of soft starters!

Guest: Chase Boehlke - Motion Control at Siemens.
Host: Chris Grainger
Executive Producer: Adam Sheets

Additional Resources:

Show Notes Transcript

In this episode Chase Boehlke gives a great breakdown of what a soft starter is and where they fit best in industrial settings. He walks us through how to properly size the solution as this can be an area that people struggle with. 

He digs deep on applications to help understand when soft starters are not the best solutions.   Finally he reviews when other alternatives should be considered. Chase brings a tremendous amount of knowledge to this topic and we hope you find the information helpful. Thank you Chase for shedding so much light on the exciting topic of soft starters!

Guest: Chase Boehlke - Motion Control at Siemens.
Host: Chris Grainger
Executive Producer: Adam Sheets

Additional Resources:

Chris:  00:00   

Welcome to EECO Asks Why. A podcast that dives into industrial manufacturing topics and spotlights to heroes to keep America running. 

I'm your host, Chris Granger and on this podcast, we do not cover the latest features and benefits fits on products that come to market. Instead, we focused on advice and insight from the top minds of industry because people and ideas will be how America remains number one in manufacturing in the world. 

All right. Welcome to EECO Asks Why. Very excited for this episode, we're going to be digging into the topic of what is a Soft Starter and how can I best apply them in my facility. So with us today, we have, Mr. Chase Boehlke from Siemens, very excited to have Chase.

So welcome Chase. 

Chase:  00:46   

Thank you. 

Chris:  00:47   

So just to get us started, can you give us, a basic general breakdown of what a soft starter is? 

Chase:  00:55   

Yeah. Sure. Basically there's three types of ways to get a motor moving in today's industry. You've got a starter which is just a contact and some overloads and line protection, then you've got a soft starter and then you've got to drive. 

What a soft starter does is it always runs at the main speed of the motor. So if you have an 1800 RPM motor, the soft starter will eventually get that motor to 1800 RPMs. Where it differs from a general starter is that a soft starter we'll slowly raise the voltage with its electronics, and what that does is it slowly gives the motor more and more torque and it gets up to speed.

So where this is useful is fans, pumps, conveyors, anywhere where you need less than the maximum torque output that the motor can provide as it's speeding up. 

Chris:  01:45   

Okay. That's a good breakdown. So we call this EECO Asks Why for a reason, cause we want to give our listeners a more in depth, purpose behind the equipment that they're utilizing. SO why would I want to use a soft starter, typical applications, you just walked through fans, pumps and conveyors. Are they the primary applications? And just looking for more of the why behind the making the decision here. 


Chase:  02:15   

Absolutely. So in a fan or a pump, we most often say fans and pumps for, soft starts, but it doesn't always have to be a fan or a pump.

The idea here is a software provides you with a slowly increasing torque. A lot of people say that always a soft start to limit current. Limiting current, actually a by-product of a soft start. What you're actually going for is that reduction in torque upon start-up. So if you have a fan with a belt and pulley system, the last thing you want to do in a lot of cases is have a 50 horsepower motor doing a full load start and a gigantic inertial load.

It's just going to skid the belts where things out. The same goes for pumps, if you start pumps across a starter, you can get severe water hammer and it ruins mechanics and it damages things. Where is if you have soft starter now that motor is slowly increasing torque, everything comes up to speed. Nice and smooth. 

Chris:  03:08   

Okay. Thank you for walking us through that as well. And that kind of brought up. So we've talked about a couple of applications that it does make sense. We're about applications, that it wouldn't make sense, but what would those be? 

Chase:  03:21  

That's actually a very simple answer as well. So one reason you would never want to do a soft start is where you need to continuously vary the speed. A soft starter is only really good to start that load with an increasing torque, but once it's up to speed, it cannot vary the speed. It's always going to give out the frequency that is put into the soft start. And so if you do want to vary the speed, you would have to change the gearbox or change the motor speed.

Chris:  03:48   

Ah, got you. So it would have to be a mechanically driven change at that point on that application for a speed change. 

Chase:  03:55   


Chris:  03:56  

 Okay. So let's talk about already I've determined that a soft starter is what I need for my application. Definitely want to go forward with it. What do I start when sizing one up for my particular application?

Chase:  04:11   

There's a couple of things you want to look at. The first one is the amount of starts per hour or per day, things like that. There's two main kinds of soft starts in general, out there in the US and one of them is a solid state unit that is fully solid state, meaning it's running off of its electronics 100% of the time. And those units can do as many starts per hour, typically, as you want, but the most common and less expensive soft starts actually switch over to an internal contactor once they're going. And it's a much smaller contactor because you're not trying to make and break load under full speed.

So in that case, when you're sizing it, you would definitely want to know how many starts per hour. Otherwise those little electronics that are getting the motor up to speed are going to overheat. The second thing you want to know is what is your motor name plate data. Again, and again, the very first thing that you're ever going to want to ask for is what is the motor name plate?

Not all motors are the same, not all motors have the same voltage, the same current, same poles and the same speed and these things matter to a soft start. So you absolutely have to know the current, the voltage, if there's a service factor and how many starts per hour. 

Chris:  05:30   

Okay. Now mentioned that contact or bypass is that what we hear people talk about? A lot of time, a soft starter with a bypass, is that what they're asking for in that situation? 

Chase:  05:41   

So in general, you have a soft start with an internal bypass, and that just means once that soft starts up to speed, it switches over to that small contact that we talked about. And then it can run all day long, extremely efficiently, it's just a starter at that point. That's sometimes what some people mean. 

The other way that people mean it is if they have a soft starter in a panel. If that soft starter were to fail, they would need to fail over to a standard starter, which means just a contact or set up. So if the soft starter failed, they would want, what's called a two contactor bypass or a three contactor bypass. And what that allows for you to do is to run the load and in some cases be able to replace the soft start. So if you have a load that just absolutely cannot stop for whatever reason, then you would want to have what's called a bypass system. And as a matter of fact, when you're doing drives, sometimes you actually have a soft starter bypass for the drive.

Chris:  06:39  

Very good. Okay. What about protection from overload short circuit protection. Does that scheme change with a soft start application? 

Chase:  06:48   

Yeah. So on a starter system, you're going to have your line protection. You're going to have your soft start and then you're going to have your load. Okay. Or your overload. And sometimes that line protection has a motor overload built into it and a starter. Soft starts and drives are also pretty similar in a soft start you're going to have a line protection device and you should always go to the manufacturers, requested line protections for that, whether it be fuses, circuit breakers, or a combination, but the soft starter will always have the motor overload protection built into it and so does the drive. But in the soft starter, you're definitely gonna want to put that in because if your motor is pulling too many amps, the soft starter is then the device that's going to protect your motor. 

Chris:  07:29  

Gotcha. Very good. Thank you for walking us through that Chase. Very good information there. Let's move to control for a soft starter. You have different options for control of any, a lot of these smart devices these days. How does that play into factor with soft starters? 

Chase:  07:46   

So one of the things that most people like myself would ask you or the customer in the first place is how do you want this thing to run or to communicate?

And what we're asking is, do you want to do hardwire control? Meaning do you want to have IO running straight to the soft start of physical 24, 120 volt IO and buttons that you can push to make it go stop? Things like that? Another very popular method is to run it over the network now, right? So you can have a programmable logic controller, a PLC, run it remotely and in that case, you'd want a network control.

One of the most common networks today is ethernet, and there's several different protocols that needs in it that people can use and that different manufacturers support, we use Profinet, there's several others that are available too. And that would be an example of network control soft start. In addition to that, you could have it run what we call hand-off auto mode, that's a very common industry term. So off is just obviously off and most typically hand mode is going to be those manual switches and IO points running directly to the drive with good old fashioned MTW. And then auto would typically be a network control device. 

Chris:  08:55   

Very good. You walked exactly where I was hoping that you would to cover all the different areas. So thank you for that control. Hopefully that brings some answers to some questions for the listeners out there.

Now let's say we had this soft starter installed. We're ready to go out. We have our motor installed on the application and we're wanting to go through a startup. What does that typically look like for these types of applications and devices? 

Chase:  09:24   

Sometimes it depends, or I guess it rather depends on who put it together. Sometimes the manufacturer can put that together, like Siemens, who I work for. Other times it could come from a panel shop or a panel builder, and sometimes the end-user can assemble it themselves or put that soft starter in a pan, or it could be a wall mount unit. 

No matter what the situation, if you're the one starting this thing up, we always ask. It doesn't matter who made it. It doesn't matter who put it together. We always want to make sure that everybody verifies all the connections and verifies that the safety checks have been done. Okay. That is the most paramount is to keep everybody safe.

When you power these things up, I always tell people don't be anywhere near it. The very first time you power up something with a bunch of large capacitors in it, you have the potential for failure. So with safety being said has always been number one. Always keep the panel closed if it's in a panel, those kinds of things, but when you do power it up, everything's okay.

The first thing you want to do is you want to review the parameters. Most soft starters have a list of parameters or settings that you would go through, or they have dip switches for the more simplistic units, but make sure that those are set up properly. 

There's two different main modes that software is typically run in. Then, they either have what they call a time start. So if we have a typical 460 volt soft start, it goes from zero to 460 volts over some set time. And that voltage just increases, and the motor will pull as much current as it needs to get to the torque that it can get to. The other ways to do what's called a current limit start, the soft start will just manage the amount of current that it can supply the motor and vary the voltage to keep the current slowly rising. And then there's sometimes a third mode, which is an intelligent mode, but those are the two main modes. So you want to make sure that you have the right mode selected or you could have a problem.

Like I said earlier, soft starts, typically provide a raising torque over time, but they don't always pull less current, which can be an issue, if they're not set up right. So once you have all that set up and once you have your parameters and your systems set up, the first thing you want to do is you want to do a bump test.

And that's how we refer to it. We mentioned that the motor spinning the right way, you don't ever want to start up a starter, a soft start drive, anything that spins a motor and tell it to go full boar in the wrong direction. Sometimes that can be catastrophic, right? So we want to do a small bump test, make sure that everything's going the right direction. Then we start things up, go ahead and load test it, make sure everything's running the way it should and then we can go on with it. 

Chris:  12:03   

Wow. You did a great job of walking us through that startup. And I really appreciate how you started us off with those areas around safety. We really stress that on EECO Asks Why, and tried to, ultimately at the end of the day, we want all of our heroes go home. So a good point. Love how you walked through the different scenarios. This is an off the wall question. Is there a minimum size of motor that users should think about when they consider looking at a soft start application? I typically think of softs starters with, relatively good size loads but I didn't know, is there a bottom end where it really doesn't make sense to even think about a starter for typical applications?

Chase:  12:46   

I would say no, it just depends on the load. If you have a very, fragile load and you're trying to start that load slowly, if you started with a server, it can still break things. If your load was made out of toothpicks for instance, and you only needed like a quarter horse, you don't want it to give it a quarter horse you're just going to snap everything apart, right? 

So soft starts no matter what the size can be useful. As far as sizing yourself starts with the motor, every manufacturer is going to have a different size ratio. That could be the maximum. Siemens has their limits for size of motor to soft start and so do other manufacturers. The reason that's important is because once again, the soft starter is the overload protection device. And if the current sensing devices inside of that soft starter can't accurately measure the current going to the motor, then you may not be possibly protecting your end device and that can resolve problems, obviously. So there's generally a limit that you should look at your manufacturer. If I have a one horsepower motor, I may not want to go over a two horsepower, a three-horsepower soft start.

Chris:  13:53   

That makes sense. Very good. Thank you for that, cause you're right. I guess there is no limit so far on the small end, depending on that, the right applications. 

And just with your experience out there, Chase, you've seen a lot of things in the industry. Let's see you work for, a great manufacturer, you're in front of a lot of customers. What mistakes have you seen users making when it comes to applying a soft starter in industry and just trying to help people get better. So, any advice or any things you've seen that, people could potentially learn from here? 

Chase:  14:28   

Yeah, always learn from other people's mistakes and learn from mine. A soft starter got sized one time for a very large fan, really high inertia, I think it was like six or 700 horsepower. And the soft starter was set up to do a typical soft start, which, like I said earlier, raises the voltage from zero to 460 over a set amount of time. As you can imagine, it's like a Brown out for a motor once you're under voltage during the motor. And so it can pull a lot of current. So in a high inertia setting, sometimes you want to set up for a current limit start instead, so that you're not pulling too much current.

In this particular case, the customer had been trying to start up this unit over 30 seconds. And so the motor would just pulling truckloads and truckloads of current, and eventually they blew the main breaker coming into the power building. Which is pretty impressive. So they called me out there and they said, let's see it again.

And they started up again. So it was about five seconds into it. I saw the lights actually starting to dim in the room and just said shut it off. So after some quick setting changes, we put it in a current limit setting, and we set it for 150% current limit. Then all of a sudden the problems went away.

Make sure you're picking the right device for your application, number one, and number two, make sure that the settings are correct and people like us again, I worked for Siemens, so if you want us to come out and look at things, we're happy to do that kind of thing. So we're relying on your local experts in general. We're more than happy to come out and see the new application. 

Chris:  16:07   

Absolutely. That was a great story. I was thinking back to my motor repair days. We liked it when guys did stuff like that. 

Chase:  16:15   

Yeah. We'll sell you another one. Don't worry. 

Chris:  16:16   

That's right. Chase, man. Thank you so much for your time today. A lot of expertise that you dropped here, a lot of knowledge, hopefully this is a valuable piece of information for our listeners and really appreciate your time again. 

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