Posted by Clint Combs on January 21, 2010 at 1:19pm
A couple of years ago, Pentair introduced a motor to the pool industry that is a great improvement in efficiency as compared to what we have been calling “energy efficient” motors. This motor is referred to as a permanent magnet synchronous motor (PMSM) and it is used on their IntelliFlo line of pumps.To truly appreciate why this style of motor is more efficient, one needs to understand what a power factor is.First, all motors use magnets in order to turn a rotor. They work on the principle that opposites attract. Thus, the south pole is attracted to the north pole and vice versa. If you were to take a large horseshoe magnet and place a boy scout style compass in between its ends, the compass needle would spin to align itself with the horseshoe magnet’s magnetic field. If you could then reverse the polarity of the horseshoe magnet, the compass would spin 18o degrees and realign itself. If you could continuously reverse the polarity of the horseshoe magnet, the compass would keep spinning. This is the basic idea behind how a motor works.So, how do you reverse the polarity of a magnet? One way is to use an alternating current to create an electromagnet. The following graph shows an alternating current. The current (and voltage) alternates from a maximum positive value down through zero to a minimum negative value and back up in a continual cycle according to the familiar sine wave pattern:
As the voltage and current alternate, so too does the polarity of the magnetic field. By using this type of continually reversing electromagnet, the compass needle (or rotor) will continuously spin inside the magnetic field.An interesting thing happens when you pass an alternating current through a coil of wire that you use to create an electromagnet. The coil imposes a restriction upon the power. The voltage passes through faster than does the current. In other words, the current is said to “lag” behind the voltage. This means that the peak voltage no longer occurs in sync with the peak current. The peak current lags behind by a small amount of time. This lag is indicated by the phase angle φ in the following graph.
This is very significant. From Ohm’s law, recall that Power equals voltage times amps (P=EI). This means that at any given time, you are to multiply the voltage value in the above graph times the current value to calculate the power value. Notice that when voltage and current are both positive, the power will be positive too. Similarly, since a negative times a negative is also a positive value, when both the voltage and current are negative, the power will again be positive.But when the current lags the voltage, there will be times when one will be positive and the other negative. In these cases, the power will be negative. (Since a positive times a negative is negative.) This can be seen in the above graph where the power sine wave dips below the zero line. In these cases, the motor is no longer converting electrical power into mechanical power to turn a pump, it is turning mechanical power into electrical power. It has for this period of time, become a generator and is trying to feed power back to your power company. Your power company doesn’t like this, nor do they pay you for it. It pollutes the power in the neighborhood by screwing up their nice sine wave power and you simply pay for power that you don’t use.To counter this problem, motor companies build “energy efficient” motors that capture this power that induction motors try to stuff back down the power company’s lines and store it in a capacitor so it can be reused by the motor. This is a small advance in efficiency.A giant step forward was taken with the permanent magnet synchronous motor. With this style of motor, you don’t use a coil to create an electromagnet. You use permanent magnets instead. Since there is no inductive electromagnet, there is no current lag. This means that the voltage and current stay in sync. Since they are in sync, they will either both be positive or both zero or both negative. There will never be a case in which one is positive and the other is negative. Because of this, their product (the power) will always be positive as well.The bottom line: efficiencyAn induction motor is around 20-30 % efficient. An “energy efficient” motor (with a capacitor) is around 40-65% efficient. A permanent magnet synchronous motor (PMSM) is around 90% efficient.
Since this post is about motor efficiency, not just about the Pentair pump (which is a good pump!), I actually prefer the Hybrid pump (not available in all areas. Can be seen at www.hybridpumps.com I do not work for them or have any interest in the company other than I like their pumps and use them!).
If you really want to see what an efficient pump is, spend a little time on their site or give them a call! I am using one of their X2 pumps on a 25,000 gallon pool with solar, 18" spa spillway, suction side cleaner, 4 wall returns and a large waterfall, and drawing just over 2 amps! Pretty impressive pump!
Awesome information, and thanks for putting it in terms that almost anyone can understand. We use almost exclusively intelliflo pumps, but for much more reasons then efficiency, and some that might even out way the efficiency. First, they are, because of the design, much more quiet. In addition to being more efficient for any given run speed, since they can be "tuned in" to exactly what pump output you need no energy is wasted. Equate this to driving your car, you would not control the speed of a car by putting the accelerator on the floor and then ride the brakes to control the speed, but almost every pool/water feature is controlled this way by valving to control flow. One pump can also do a multitude of jobs by valving and adjusting speeds. Any fluid system is also more efficient the slower the velocity of the water (almost exponentially decreasing friction), so you are able to get enough turn over rate at a snails pace by running the pump 24hrs a day while costing you much less money. Lastly maybe the most overlooked advantage to a VS pump is the ramp up and down in speed when turned off and on. Turning off and on plumbing systems with a lot of water in transit especially when the typical pool is designed improperly and velocities are high, causes a tremendous impact to the entire system. Everyone has seen the pump basket that shoots water out of it when a pump is turned off. In larger commercial systems with 6-8-10" plumbing, I have seen filters the size of a volkswagon jump off the floor upon start up or shut down from the impact. An inteliflow or Acudrive equipped commercial system ramps up in speed and down in speed eliminating all the impact. Equate that back to a car, you would not slam the accelerator to the floor for take off (at least not all the time) or slam the brakes and skid into a stop, to do so would wear out the brakes, tires, and engine, and be less efficient. Same holds true to pumping systems. If you are not already a believer in Pentair's Inteliflo pumping systems, you better catch up. Also make sure to do your research, not all advertised Variable Speed pumps are PMSM design, nor do they have infinite speed choices.
Yes David,
If you had two identical pools, one with a 3 hp Wisperflow and one with a Intelliflow running at full speed, the Intelliflow would use about 30% less power. Power is generally measured in watts.
Although the the PMSM is similar in design to some DC motors, it actually uses a driver that converts single phase 220v to three phase. It has a three phase AC motor.
I realize that the PMSM motors (mainly with the Intelliflo pump) realize a significant amount of their savings due to the ability to modulate the speed the system runs at. So I'm not looking for that discussion, but more along the lines of the last paragraph of my previous post... a 3 hp standard single speed motor vs. a 3 hp permanent magnet motor running at full speed.
Also aren't the permanent magnet motors DC? How does this affect everything?
How does this affect the electrical consumption (watts)?
Is it a directly proportional relationship?
ie. a standard running 2-3 hours consumes the same watts as an energy efficient motor running 4-6.5 hours, and a PMSM running 9 hours?
I have seen the incredible results of the permanent magnet motors, and am not questioning the technology, I am just trying to learn more about exactly why they are so much more efficient.
The efficiency for the Pentair permanent magnet motor is quoted to be 30% more efficient than a standard Energy efficient motor. So does this mean that if I am running a full-rate 3.0 hp pump and swap it out for a permanent magnet motor and run it at full speed (3.0 hp) I will be consuming 30% less electricity?
Comments
If you really want to see what an efficient pump is, spend a little time on their site or give them a call! I am using one of their X2 pumps on a 25,000 gallon pool with solar, 18" spa spillway, suction side cleaner, 4 wall returns and a large waterfall, and drawing just over 2 amps! Pretty impressive pump!
If you had two identical pools, one with a 3 hp Wisperflow and one with a Intelliflow running at full speed, the Intelliflow would use about 30% less power. Power is generally measured in watts.
Although the the PMSM is similar in design to some DC motors, it actually uses a driver that converts single phase 220v to three phase. It has a three phase AC motor.
I realize that the PMSM motors (mainly with the Intelliflo pump) realize a significant amount of their savings due to the ability to modulate the speed the system runs at. So I'm not looking for that discussion, but more along the lines of the last paragraph of my previous post... a 3 hp standard single speed motor vs. a 3 hp permanent magnet motor running at full speed.
Also aren't the permanent magnet motors DC? How does this affect everything?
How does this affect the electrical consumption (watts)?
Is it a directly proportional relationship?
ie. a standard running 2-3 hours consumes the same watts as an energy efficient motor running 4-6.5 hours, and a PMSM running 9 hours?
I have seen the incredible results of the permanent magnet motors, and am not questioning the technology, I am just trying to learn more about exactly why they are so much more efficient.
The efficiency for the Pentair permanent magnet motor is quoted to be 30% more efficient than a standard Energy efficient motor. So does this mean that if I am running a full-rate 3.0 hp pump and swap it out for a permanent magnet motor and run it at full speed (3.0 hp) I will be consuming 30% less electricity?