Watch this video to learn how our customizable brushless blowers can help you save energy, improve life and perform with precision.
For your convenience we have transcribed the webinar below.
Introduction: About AMETEK Dynamic Fluid Solutions
Hello everyone and welcome to the webinar, customizable brushless blowers for energy savings, improved life, and precision performance. My name is Christina Thomas, the marketing manager for AMETEK Dynamic Fluid Solutions and our host for today's event.
Now I'd like to introduce today's presenter. Kevin Martin is the Applications Engineering Manager for AMETEK Dynamic Fluid Solutions. He is an electrical engineer and, he has 20 years of vacuum motor and brushless blower expertise, empowering him to recommend the best methods and tools to understand airflow and end product design.
Next, I'd briefly like to introduce you to AMETEK Dynamic Fluid Solutions. We are a manufacturer of blowers, motors, pumps, and fans. For more than 100 years AMETEK Dynamic Fluid Solutions has been helping companies build products that need to move air in many applications, including combustion, transportation, medical devices, and specialized industrial. Our team of air moving experts is customer focused and quality-oriented with experience developing custom solutions for complex end products. We have worldwide sales representative support, and three manufacturing sites in the USA, China, and Mexico. Headquartered in Kent, Ohio, we are a business unit of AMETEK, Inc, a leading global manufacturer with annual sales of approximately $5 billion. With that, I'm going to hand it over to Kevin to get us started with the presentation. Kevin…
Basics of How Brushless Motor Control Works
Thanks, Christina. I'd like to start with just the overview of how basic brushless motor control works, and how a brushless motor works in general. Then once you understand how it works and how we can control it, we can dive into how those things give you the long life and the improved efficiency and the customization that only a brushless DC — or BLDC type of motor can offer.
So let's start with the basics. In this diagram, you're seeing how we start with, even over their AC voltage, 120-to-130-line voltage, running that through a bridge rectifier. Refuse it for safety, then you basically have a DC voltage out of that. If you're doing a lower voltage DC like a 12 or 24 volt, obviously there is no bridge rectifier, but it is fused for protection, so we just use that DC voltage. All our motors then have a digital controller that contains all this farces to actually do the control of the motor. To the left, you can see in the block diagram, most of them then have speed control and other interfaces to the outside world, which is what we will really be talking about today, is how you control it, what feedback you get and why you would want to do that.
So, you have the smarts of the signal process and you run it through a three-phase inverter that then drives the motor itself. You don't have to, but most motors do use hall sensors is outputs so that you know where the motor is being positioned as you spin the rotor. Then we give a PWM signal to the motor to make it spin. Let me go into a little more detail on the next side about that.
So, as you see on this simplified motor construction view in the middle is your permanent magnet and then the outside is showing all of your windings or coils. In this example we use a three-phase motor, so there's three coils A, B and C and then you take turns, polarizing those coils it make an electromagnet so that the north and south pole of the permanent magnet. So, you basically chase it and they circle just like you're playing tag and you always wanted to catch somebody. That's really how these motors work. We are controlling then what set wires get activated, letting current flow through them to drive the motor to move the magnetic field around the motor so that the permanent magnet is always trying to play catch up and that's what makes it spin. So, there's magnetic forces between the two magnets, a permanent magnet in the rotating electric magnetic field that you are inducing into the wound stator is how that basically works and depending on how you apply your DC voltage, you can make the motor go at different rates. You can apply different amounts of torque. You can make it spin in different directions, all because we take over that control and we are a digitally pulsing, the different coils at different times.
Speed Control and Acceleration
So now that you understand basically how it works, let's talk a little bit more about how you can control it. As you saw in the previous diagram, most brushless motors have a speed control option, so you can control speed and even with that, acceleration. So how does that work? You basically have options for zero to 10 volt DC signal into the analog signal inputs, on the top. You could put a PWM signal lane, many older industrial controls was done with a four to 20 milliamps signal and most every one of our blowers has what we call a mechanical control, which is basically an internal potentiometer that is used to set the speed.
So, because we want to isolate these speed control from the rest of the motor for noise considerations, we don't induce noise. We use optical couplers, and we isolate the inputs from the actual motor control, as seen in the circuit. So, you basically input your speed control signal, no matter what form it is and it goes through a comparator and then to an optical coupler and that is used to control the blower. Then on the tack outside, so that you can see what speed your motor is running at. We take one of the signals from the hall sensors and we use that to generate a tack out pulse and we run that through an optical isolator to protect any noise and cross signal contamination. So, everything is optimally isolated for the cleanest signal and best control.
Different Ways to Control Speed
There are multiple ways to control the blower speed, but one of the most common is a PWM signal. This is an example on the left, where we were using a 12 volt amplitude PWM signal. And then as you change, the DC, which stands for duty cycle from 25 to 50 to 75. You're basically changing the equivalent voltage output to the motor and in this case, the motor control circuit. So, if you do a 12-volt signal amplitude with a 25% duty cycle, that basically gives you a three volt out, then a hundred volt would give you a 12 south a hundred percent duty cycle.
Now, when you're dealing with a PWM signal, there are really three factors. There are, of course the amplitude, which is the base voltage you are using. There is the duty cycle. Which is what percentage of that full pulse, are you going to use. Then there's also the frequency. How often are you going to give it a pulse? All of those factors need to come into play in certain controllers, have certain limits to those and that all depends on controller to controller. So, you must be careful about that so that you have the right PWM signal when you use PWM.
We make many blowers for combustion applications where they are premixing gas and air in the blower itself. So, because of that, on the PWMs, the PWM signals can be what we call, pull up or pull down. So, what that means is that if you pull up the PWM signal, that if for whatever reason you were to lose speed command and that wire were to get cut or stopped working, but you would still want that blower to run full speed. It's common in combustion because you want to clear any gasses out of your system. So that's what a pulled-up means, as we pull it up, to pull speed.
However, not everybody wants or needs that for every application. So, as another option, we use our speed command, to either pull it up or pull it down, which means if you lose the command signal, you go to zero, pull down. If you lose speed command and you're pulled up, you go to full speed. So, with that control you can control acceleration because we are individually controlling the pulses as we switch those coils around to some measure, there are some mechanics involved, like mass and everything else that goes into play from the physics side. But you now though you have control as to how quickly you can accelerate and decelerate.
You could do breaking, you can electrically break the motor to slow it down by starting to give pulses at some of the other poles, to stop the spinning. Like I said, you can change the overshoot as well, if you want to get there within the mechanics of the motor, you can get there very fast and maybe deal with a little bit of overshoot of that signal and you don't really care because you just want to get there fast.
Also if you want to overshoot, you can get there slow. Those are all acceleration features or ramp up times that you now have precise control over when you are dealing with a digital brushless blower. As an example, if you look at the chart on the right, you can see the green line is saying I applied 10 volts. How quickly did it get there? I got to the 10 volts at what rate? This is showing the different controllers, get there a little bit different rates, and that they're tuned a little bit differently. So, this is what we call blower tuning, like acceleration or ramp rates or overshoot. Those are all tuning parameters that we can control with our digital signal processing.
External or Internal Pot
Another option that many of our AMETEK blowers have are in the mechanical sense, where if you don't want to use a wire, like a zero to 10 or PWM or a 4 to 20 milliamp, they basically all take wired connections to the blower. So, a mechanical connection basically means you have a potentiometer built into the blower itself, that you can change to different positions. That is what you use to control your speed when power is applied. So, we offer two options there, your internal pot, the potentiometer is right on the control board. But we also have, an option that you can do an external pot where we can bring the wires out so you can put it on a rotary switch and you can manually control the speed externally with that same internal pot feature. So there is internal and external and they basically do the same thing.
Open vs Closed Loop
Once we start talking speed control, there's two different things you must take into consideration. Is it an open loop blower or a closed loop blower? So, is there an internal feedback for the motor or not? So, if you, as an end-user are going to close that loop yourself, like a PID loop is typically used. We can use our blowers in an open loop so that we don't have two loops competing for speed control. So, an open loop is we as controller, do not close the loop on speed. So that allows an external controller to close that loop if desired or you can just let it run and the blower will speed up all based on the load of the air system.
But when you do an open loop, your performance, then now varies because you're not controlling the speed of the blower. It's all about the fan laws and speed and the fan system and we can talk about that in another video in more length. So, basically without closing the loop, you are now more subject to changes in input voltage and load of the system, which is basically the air density changes, amount of air you're moving, as filters get dirty, the load is changing. All of that affects what we call system impedance and all of those things then come into the factor so that you don't have the precise control of the speed of the motor to get the precise air performance, if it's a blower.
So how we do this is, the max speed of the motor is set up at seal conditions that means there's really no air moving or no load. So sealed is no load and that determines what the maximum speed of that motor is. And again, we can control this, this software, there's several reasons doing that. One of which is a safety reason, because the blowers are not always being controlled, you can set that top speed so it can't get out of control and go crazy. We do that for thermal protection so that on the open end, it is doing more work and is drawing more energy. We can look at all the thermals of the windings and of the controller and then we can set limits to how much power you can push through it so that you don't overheat your motor.
The operating speed is less when it’s sealed than when it's wide open, just think of doing a lot of work. If you're running on a treadmill, it is a lot easier and you can run a lot faster when the setting is light, but then as you crank up the tension on your treadmill, you're adding more load which makes it harder to run fast. So that's the same way a motor works. On the closed loop blower, as you want even more control you, we can close the loop of speed. So basically what that means is we are now constantly monitoring the motor's speed as this diagram is showing, and there's a feedback loop. And then we then can always give you a motor or blower that is running at a certain speed. Even if the line voltage changes, the load changes, different things change because we are monitoring this feed directly. When our loop, we can always tell the motor to work harder or pulse it longer, and we can control that speed, whereas you can't do that in an open loop system.
Closed Loop Example
So, it really makes a big difference when you're trying to do an industrial control system. A prime example of where closed loop is most important is when there are line to line variations. If you say you have a 120-volt AC signal driving your motor, we all know once you look into the details that that voltage is not always 120 volts, it can dip down to 110, it can dip down to 108 or it can go as high as 130. So on an open loop blower that line voltage changes and your DC voltage to the motor is changing. So your motor is speeding up and slowing down all based on the stability of the line voltage. But when you go close loop, we take all those variables out. We can set it up so when you apply a certain speed command, you will get a certain speed. Regardless of what the DC voltage is. So that is the biggest advantage of a closed loop system, is you can give common performance as line voltage changes which is very important in a lot of applications.
How to Calibrate a Blower
So, let's talk a little bit more about calibration and what that means as you calibrate a blower. As this chart is showing, and you can see the top yellow line is where you are set to a very small orifice. If you notice this as a 3.125 orifice, 'max pot' means set to the full speed. You can see that this blower full speed on a 3.125 orifice, which is basically the system impedance. So that is dictating how much load and air the blower is moving, as this blower goes around, 23,000 RPM, but as you look at the orange line, now then you open that up, you change the system impedance to allow it to do more work because it's moving more air. Your top speed goes down, because again, like the treadmill, you have a lot more work to do and the motor can only put out so much power, so the overall speed at the maximum work condition drops.
So if you look again, it keeps dropping so as you open up the blower, the maximum speed of the blower will drop, but we can calibrate a blower, so that would be the blue line. We then look at what that max speed will be at a certain load point and instead of giving you hitting max speed at seven volts on the gray line, we can now give you that max speed at 10 volts. So that gives you a longer gentler slope of your speed command which will give you have better control. So, each change of voltage now represents a smaller change of speed and that gives you better control of the blower.
Now back to that same point, the orange line in this graph is showing the maximum pressure you can get out of the blower. So basically, when it's sealed, you're getting the orange line and it’s relatively straight. That means you're basically getting the maximum power out of the blower when you have a nice straight line and you're looking at a flow curve. Which means you're always pushing it to the maximum amount, but then as we start calibrating it down and we start saying, we only want a max speed of 19,000 RPM, you can see the performance starts to curve because you're now hitting that max speed. The blue line then shows a max speed at 18,000 RPM, and then you're getting of even more curve and you're flattening out your overall slope of your performance curve by calibrating a blower to certain max speeds. Again, this is very common in a lot of industrial applications. They want that control of their processes better to make sure that they know exactly what they're going to get out of each blower product.
Customer Example - Purge Cycle
One other thing you can do is because now we have a digital controller, and we are on a closed loop system. We can really do all kinds of crazy things with the speed command, like this chart is showing. This is a real customer application, and in this case, the customer wanted the blower to do a purge cycle. So as you can see, if it's zero to half of a volt, the blower ran full speed. They wanted to always hold it off at basically one volt. So, between half a volt and 1.5 volts, the blower was basically off, zero speed. If you look at the left-hand side of the left chart the vertical axis is showing the speed and the horizontal axis is showing, like in this case, a zero-to-10-volt speed command input.
Then they wanted the blower to start at a volt and a half. So, at 1.5 volts, we gave them a 4,000 RPM on this motor and then you can see a nice, very straight linear response from 1.5 to 7.5 volts to get their full speed. And then when it’s above 8 volts, they wanted to make sure that their blower was running at full speed. It's kind of a funny looking chart, but this is the advantage of a digital controller with a closed loop system in a custom software where you can do these types of things to match exactly what your system needs it to do. There's lots of reasons for this, but you can see there's all kinds of things.
We often do a step response, so at 2 volts it runs at a certain speed and then at 4 volts it runs at a certain speed and at 6 volts it runs at a certain speed, and that is a step speed response. So, as you're learning about blowers and you’re asking and talking to your suppliers for your blowers, you should make sure you ask them, can I do speed control? Will you customize it for me? Because I need exactly this, but not every brushless blower manufacturer allows you to do this level of control. But here at AMETEK we have been doing this for years and we think it's the best way to go to try to suit each system best for each application. So, that's how speed control works, how blowers work, and some of the advantages of why you would want to do it. So, at this point we would like to turn it over to any questions that may have been sent in. So, Christina, I'll turn it back over to you to see if we got any questions.
Question and Answer Session
Sure, so we do have a few questions, but of course we'd love to hear from you. So if you have a question at any time, simply click the chat bubble button on the left side of your screen, then type your question into the box and hit the send button. We will respond to your questions within 24 hours. We also encourage you to reach out, to schedule an innovation conversation with our technical team to further discuss your specific application. So now let's go ahead and get to our first question.
Are the motor windings a Y or Delta configuration?
Yeah, that's a very good question. Most brushless motors could be wound either way. There are some advantages as far as current draw goes and some trade-offs from that, which are how much current the motor is drawing and the level of control that you can get out of it. AMETEK typically uses a Y configuration, which is the example we showed at the beginning of the slides. That was a Y, if you remember, you activate two legs at a time, should that voltage just kind of float in a Y, if you look at those three windings that's how you get the Y out of it. They could also be what they call a Delta, but we at AMETEK typically just use a Y configuration.
Does every blower manufacturer offer custom programing?
Yeah, that's a good point. No. I mean, just because you buy brushless does not mean that the main attraction will allow you to even work with them to customize it. Many blower manufacturers, just mass produce blowers, and they don't give you that option. We here at AMETEK, think it's super vital and we have the capability, so why wouldn't we offer it. That way you can allow a fine tuning and matching between what the blower does and what your system needs, that way you really get the best operating point, improved efficiencies, and life out of that situation. I forgot to mention that one of the advantages of a brushless blower is life, because you can now don’t always have to run it at full speed now that you have all these speed control options.
Now, as you run slower, you are just increasing the life of the motor because you're not always running it to the highest speed and many of the failure points comes down to bearings. So, as you're running these for a long time at very high speeds, you're negatively affecting the bearing in life, which is often the failure point of a brushless blower. So, with the speed control options you can tune your system to the exact operating point, you're not using power or speed that you don't need, is how you can control and increase the life of your motor. I forgot to mention that. So, thanks for the question that has spurred my thought.
Does every blower have the same control options?
That's a great question and the answer to that is no. Every company uses different types of controllers and different types of things, and here at AMETEK, a lot of it is just based on size. So if you're doing what we call a small 22 frame motor, which is like an inch and a half diameter, you have a very small amount of real estate on your controller. So, you can't build in all the same control options, as you could on a 5.7-inch blower, which has a whole bunch of real estate that you can build a lot more controls on. So, you have to be aware of your controller and what the capabilities are for each type of motor and brushless blower you buy. It's very dependent and it's usually just on space. There are several different technologies that can be used in controllers that we use as well. We have some centralist ones, and we have some hall effect blowers, we have half wave, we have full wave. All these technical terms about speed control and controllers, but yes, we make a full range of controllers all depending on the application.
Okay, great. That's all the Q&A that we have, so that concludes our presentation and would would like to thank you all for attending!