I've been trying to model a capacitor-start capacitor-run single phase AC motor with this kind of AC circuit analysis. The thing I'm tripping up on is the back EMF from the coils in the motor. It looks like conventional theory would consider the back EMF to be modeled as a separate AC source pointing the opposite way, hidden inside an inductive coil and in phase with incoming voltage. Once the motor spools up the back EMF grows dramatically and current falls. Is it fair to say that the big increase in voltage drop seen across the start windings is mainly from the phase shift of the capacitors in series with the start windings? Or, is there actually an increase in voltage caused by the colliding waves of the two voltage sources as they meet at the entrance to the coil, much like the way waves on a lake from two sources create large standing waves at the interface where the waves meet?
Hello, The statements, schematic, and calculations are confusing; AC has + and - signs (DC!), negative is isolated, and capacitors are not electrolytic. Would it be possible to please explain the power supply form; if it is AC, which law determines + and - for it; does it mean Hot and Neutral, or even earth, where if the resistance between the earth and ground is less than
In LTSpice, the voltage source looks like a DC source even if you have it configured for AC. You can look at the text below/beside it to see how the source is configured. In this case, it says "AC 120" because it is an AC source at 120V. Also, you wouldn't want an electrolytic capacitor in this circuit since it is AC, but I don't think there is an electrolytic capacitor symbol in LTSpice anyway.
@@ElectronXLab Hello, a) The original questions were why the schematic is wrong; power source is an AC form, the ground is isolated, caps are not electrolytic; nevertheless, AC represented as a DC form with plus and minus instead of hot and neutral poles? b) If the power source is a DC type, there would not have been any currents through the components. c) Of course, the caps should not be electrolytic, where they explode, and there is no use for them. d) Finally, the whole subject matter was why the schematic shows a confusing circuit that does not comply with statements and defies physic laws? Sincerely,
@@benjaminkarazi968 I'll see if I can answer these questions for you, but I think the bottom line answer to all of them is that LTSpice requires me to enter them in that way. To make sure we are talking about the same thing, I'm trying to build an AC circuit with a couple of capacitors, an inductor and a resistor. When I say AC circuit here, I simply mean that there will be a sinusoidal voltage applied from the source at a frequency of 60 Hz - I am not trying to emulate a circuit that you might find in your house. a) To create an AC source in LTSpice, I have to use one that looks like a DC source. The "ground" point is also required by LTSpice, but it is not actually ground, it's just a common reference point b) You're right, if it was a DC source, there would be no currents after any transients had settled. c) yes, not electrolytic. I don't think there is a symbol for electrolytic capacitors in LTspice anyway d) LTSpice makes me build a circuit that looks like that (as far as I know...if anyone knows a better way, I'm happy to hear about it). You have to look more closely at the components to see what they actually are (e.g., the source that looks like it's DC is actually AC).
