Back ordered at Black Swan in CT got a back ordered email this morning, and checked Green Mountain online, back ordered. I called Woodheatstoves.com, they touched the part, and I ordered from them. I don't think the dealers stock a lot of inventory, and when the season hits, its first come first serve. Hopefully I'll get it by Wednesday. If you have a Quadrafire stove, order one to keep one on hand, if you plan to own your stove more than 5 years, its probably a good investment.
Now why does the circuit need a capacitor. I suspect that the motor in the pellet stove is an AC Induction Motor which produces torque when the angle between the alternating magnetic field produced by the stator is greater than zero. This is called slip. The article below shows how a capacitor is often included in series with one of the stator windings so as to introduce a phase shift in the stator magnetic field to increase the torque. There are also systems that only include the capacitor in the “auxiliary winding†at start-up and switch the cap out with a centrifugal switch in the rotor. See below
www.allaboutcircuits.com/vol_2/chpt_13/9.html
I imagine that a shorted cap would reduce the torque significantly and an open cap might do the same. If the cap were a start-up cap then the motor might not even move.
Why does it sometimes move backwards? I’m guessing because it has been a long time that I thought about these things.
1. In an AC-induction motor, the excitation of the stator coils causes the magnetic field of the stator field to rotate.
2. This rotating magnetic field induces currents in the rotor windings.
3. The current in the rotor winding produces a magnetic field.
4. The when the fields are not coincident there is a torque. When the torque is equal to the drag, in the steady state, the rotor moves at constant speed.
5. When the angle between the two field is positive (positive slip angle) there is a positive torque when there is a negative slip angle the torque is negative.
6. The presence or absence of the cap or a short in the auxiliary winding will affect the phase of the stator magnetic waveform relative to the rotor.
7. I suspect that with a shorted cap depending on the load and the normal “phase lead/lag operating point†one could have the stator/rotor slip angle positive rather than negative with the cap in place so that a negative torque is applied rather than positive, hence the rotation in the opposite direction.
8. If I really knew this stuff I would be writing Wikipedia articles.
!! :red:
