Capacitor function

Alan(CaliforniaRadiant)Forbes

to explain the function of the capacitor in the circulators we use (Taco and Grundfos) to my son and coming up short. As I understand it, capacitors store energy, but why would a circulator need this function?

Can someone help?

Best wishes,

Alan

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Matt

Howstuffworks.com

This may help a little.

http://www.howstuffworks.com/capacitor.htm

Mike T., Swampeast MO

It's about Alternating Current

And it's still confusing as you have to invision what happens when a magnetic field alternates...and how magnetic fields out of phase with one another interact...

People knew of AC long before Tesla devised the entire AC generation/utilization system we still use today. Because the magnetic field fluctuates with AC, the earlier attempts at an AC motor resulted in a thing that sat and quivered--not turned--unless of course an outside force initiated the spin. Many thought an AC motor a physical impossibility because of this.

A single capacitor is there to create a high initial force to start the motor turning. It is connected through a separate smaller winding in the motor and as the capacitor alternately charges and discharges this coil it sets up a second strong magnetic field that forces the motor to turn in a single direction. It is disconnected from the motor after it reaches speed. Once turning, such a motor is considered "single phase." When starting, it is "two phase." This type of motor has very high starting torque, but is not particularly efficient nor especially powerful when running.

Dual capacitors get a bit more confusing. This is the "capacitor start, capacitor run" motor. The first capacitor works as above--for starting torque--and is disconnected when the motor reaches speed. However, in this motor a second capacitor stays powering the second winding at all times. Both this capacitor and the second winding are stronger in these motors. This esentially allows single-phase power to operate a two-phase motor. The added "twist" of the second phase makes these motors smaller and somewhat more efficient that capacitor-start motors, but they do lack a bit in starting torque.

Below is a decent link.

http://www.lmphotonics.com/single_phase_m.htm

Find your son some books about Tesla--utterly amazing reading for ANY age! The genius it took to create polyphase AC is unfathomable to me.

John Van

The Capacitor is for starting

The typical circulator motor is of the "Permanent Split Capacitor" design. This means that the stator windings (the stationary windings around the outside of the motor) are split into two separate parts. These two windings are typically placed 90 degrees apart from each other. One winding is for starting, the other is for running. The capacitor is in series with the starting winding. Due to the energy storage characteristics of the capacitor, the ac current in the start winding will be about 90 degrees out of phase (think of it as slightly delayed) from the current in the run winding. This phase lag sets up a rotating magnetic field in the motor which attracts the rotor, and drags it around the axle. The field rotates because the currents are alternating 60 times a second. If you think of compass points, the rotor is first sttracted north (run winding) then a little later east (start winding) then south (opposite current through run winding) then west (opposite current through start winding), then north again as the cycle repeats. Without this phase lag, the motor could not generate any starting torque, and would never move.

On many larger motors, there is a centrifugal switch that disconnects the capacitor and the start winding once the motor has reached operating speed. The small circulators do not have the centrifugal switch, hence the permanant in Premanant Split Capacitor.

Eric

Tesla

I recommend " A man out of Time". I just read it last month. A great book on tesla.

Unknown

Capacitors

I just did a series of articles for HVAC Insider on Capacitors. Alan send me an e-mail with your address and I will send them to you very simple explanation with cartoons.

Alan(CaliforniaRadiant)Forbes

Reading Material

Thanks for all the help; my son and I have a better understanding of what they do now.

Best wishes,

Alan

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