PSC vs Capacitor Start Capacitor Run AC Motors 3

[LRME20]

I am a Mechanical Engineer, but I am the only engineer in the USA for my company, so I really need to get a better understanding of what the design differences are in the windings of the two motor types. My story may be long, but I would really appreciate any help!

My company manufactures motors. To date, we only design and manufacture PSC motors (one capacitor bank for starting and running the motor). I believe our motors are becoming too large to continue without designing CSCR motors (we are in ventilation and are turning some fairly large fans now). Of course, the problem is we have to use a much larger powered motor to turn the same RPM as a competitor's motor, with not as good efficiency. I believe the remedy for this is to design a CSCR motor to stay competitive.

The problem is convincing my European colleagues to do this. I need to be able to prove my point and make it in an intellectual manner (because that's what engineers do!).

So, the first question is more of a verification: They once tried to test a PSC motor with a manual switch to switch capacitor banks once the fan was running. I believe this is a flawed experiment, is this true? I believe the winding must be designed specifically for a CSCR motor, correct?

The design of a winding is beyond me as I am a ME... But to get a true test, we would have to design a motor with essentially two windings, offset from each other, if I understand my limited research correctly.

Could you explain maybe some industry standards for the maximum size for a PSC and when a CSCR is needed?

Could you explain how a PSC motor would perform with a smaller capacitor as compared to a true CSCR motor?

Will I be able to use a smaller CSCR motor in place of a PSC motor and achieve roughly the same performance at a better efficiency?

Thank you in advance!

 

[LionelHutz]

You seem to have proved that the blade design has the largest impact on the overall fan efficiency and the motor has little effect.

Is your issue with the motor load or the motor efficiency? Many general purpose industrial motors will be more efficient at 75% load than at 100% load so having a motor that isn't fully loaded doesn't mean it's less efficient.

As a mechanical engineer you don't understand how inertia only effects acceleration and deceleration?

 

[LRME20]

Thanks guys,

You're right Lionel, I was not thinking about it like that. There's a lot going on and I wasn't thinking correctly!

I really am thinking that the blade is at fault... I think I can draw up a good conclusion with the data I have.