My guess is that it is a normal AC reluctance motor. The shape of the motor housing indicates more components than a typical AC pump starting capacitor. My guess is that they included a filter circuit inside the motor casing to flatten the shape of the sine wave. If done correctly this will reduce pump vibration and "hum". The capacitance in the filter circuit will push the power factor up toward unity.
This makes sense to me. I hadn’t thought of this possibility.
Sounds intriguing, but if it was so easy to do all along why hasn't anyone else done it yet? From my understanding small reluctance motors are quite a bit trickier to design than a simple psc motor with a typical stator winding. The reluctance motor needs some clever switching controls to energize the 2 stator poles at the correct times to maintain rotor speed. I'm not sure how the capacitor you speak of could be incorporated. But I don't have any degrees in electrical engineering so I'm just going at this from an electric motor hobbyist level. Maybe @Amoo could explain the sicce pump's mysterious .97 PF for us
The switching of a reluctance motor happens in an AC circuit naturally because of the sine wave. On one half of the sine wave the current flows one direction through a coil producing a positive. A winding on the opposite side will be wound the opposite direction so it creates a negative. When the sine wave drops into the other direction, the polarity on both windings switches. They will always turn at synchronous speed that can be calculated using NP=120f where N is the speed, P is the number of poles, and f is the applied frequency. To create a variable speed motor (think DC pumps) it requires some clever switching to provide a variable frequency to the motor.
Possible. Unfortunately, I can't see enough detail to know how it is used. Along the bottom are 3 thermistors, 2 lower power and 1 higher power. These could be used for load sensing or for reducing stating current but without knowing the exact ratings and how they are wired I can't say more than that.
Thanks and Roger that. I knew that was how PF, induction motors, and simple non-directional reluctance motors like a Mag drive etc worked. but always thought the directional start, 'smarter' reluctance motor pumps used some more clever circuitry design to control power delivery based on load. Maybe they're a lot simpler than I thought. Can you answer this - why add the capacitor? Would it not bear a slight reduction in efficiency? And why would Sicce need to add it to reduce hum, since most of the standard reluctance motor pumps are already very quiet and this factor seems to be linked to the balance of the impeller and rotor assembly riding in the bearings more than anything to do with the drive method?
Directional start can be accomplished in 2 ways. The old fashioned way is to have some sort of mechanical stop to bounce the rotor back into the correct direction. You can also do it by using a feedback sensor to to determine rotor position and time closing of a contact so the sine wave is in the correct position in relation to the rotor.
It will hurt efficiency which is why motor manufacturers typically won't do this to help power factor. However, if you were going to be using capacitors for a different function, such as filtering or wave shaping, it would make sense to size them appropriately to help with pf.
I use Sicce Pro's on my system and they are quiet, but they are louder than typical DC pumps of the same size. A great example of wave shaping to reduce noise are the Vortech Quiet Drives. When they came out with the QD's you could upgrade the controller while using the same wet and dry sides. The noise reduction was very impressive with the 2 MP40's I upgraded this way. They went from too noisy for me to enjoy to almost dead silent.
This is a fantastic observation, you may be on to something! I need to think if/how it could be done in a cost effective manner.....
I just got off the phone with a sales rep I deal with and what he said leads me to believe you may be correct. I wasn't aware just how far the costs for the BLDC controllers has dropped. Texas Instruments recently released a BLDC controller for small (under 48W) motors that OEM's can buy for under $3. I'm sure a slightly higher power version wouldn't be much more expensive. The rectifier needed to power it wouldn't be much more than the controller.
Safe to say though Brew is going to give you solid and legit infos.
