True dat. Hardware triggered ... wait to capture a specific time span until some event happens. I'm going to use a bunch of these when I discuss synchronous motors and generators.
Is CEMF exactly in phase with the incoming supply voltage? I'm still trying to wrap my head around how the potential relay works in single phase air conditioning equipment.The typical motor has parallel start and a run windings, and the start winding branch has a parallel set of start and run capacitors, both of them in series with the start windings. The potential relay controls a normally closed switch to the start cap, opening within a second when voltage across the start winding exceeds a limit, and staying open until the next cycle. The run cap continues to supply current to the start windings throughout. The coil for the potential relay is attached to either end of the start winding, so the afferent end is located between the capacitors and the start winding. If you put a multimeter across the start coil leads, you'll find voltages that are far higher than incoming voltage, for example on a 240 V system you'll find voltage there measuring up to 380V, with forward polarity! The knee jerk response from technical instructors regarding this is that you are seeing the combined effect of incoming voltage and back EMF, like standing waves where two opposing sources of waves come together. I'm not understanding how opposed voltage sources push incoming voltage higher than the highest voltage source... For example, parallel DC batteries don't boost voltage higher than the voltage of the highest battery.... Am I correct to believe this is all about the multiplier effect of a tank circuit, caused by the phase shift of the resonant capacitor and coil impedance?
Short answer ... I don't know and I really don't know how you could determine if it is or not? The simple mathematical model of the winding consisting of the series combination of the resistive, inductive, and CEMF portions is only accessible at the top and bottom nodes, as is a real winding. Anything happening internally would be a total guess to someone with my level of physics. This being said I do know that CEMF produced by three separate windings (baring single phasing events) does indeed exhibit a relative 120 phase shift from one to another and CEMF magnitude is indeed roughly proportional to rotational speed. In later lectures on synchronous generators I'll demonstrate this effect using oscope traces.
Jim, why would the cemf be higher when the rpm is higher,but at higher rpm,rotor wires will cut less magnetic field since magnetic field is also rotating at higher rpm
Love the scope captures
True dat. Hardware triggered ... wait to capture a specific time span until some event happens. I'm going to use a bunch of these when I discuss synchronous motors and generators.
Thank you Sir
Is CEMF exactly in phase with the incoming supply voltage? I'm still trying to wrap my head around how the potential relay works in single phase air conditioning equipment.The typical motor has parallel start and a run windings, and the start winding branch has a parallel set of start and run capacitors, both of them in series with the start windings. The potential relay controls a normally closed switch to the start cap, opening within a second when voltage across the start winding exceeds a limit, and staying open until the next cycle. The run cap continues to supply current to the start windings throughout. The coil for the potential relay is attached to either end of the start winding, so the afferent end is located between the capacitors and the start winding. If you put a multimeter across the start coil leads, you'll find voltages that are far higher than incoming voltage, for example on a 240 V system you'll find voltage there measuring up to 380V, with forward polarity! The knee jerk response from technical instructors regarding this is that you are seeing the combined effect of incoming voltage and back EMF, like standing waves where two opposing sources of waves come together. I'm not understanding how opposed voltage sources push incoming voltage higher than the highest voltage source... For example, parallel DC batteries don't boost voltage higher than the voltage of the highest battery.... Am I correct to believe this is all about the multiplier effect of a tank circuit, caused by the phase shift of the resonant capacitor and coil impedance?
Short answer ... I don't know and I really don't know how you could determine if it is or not? The simple mathematical model of the winding consisting of the series combination of the resistive, inductive, and CEMF portions is only accessible at the top and bottom nodes, as is a real winding. Anything happening internally would be a total guess to someone with my level of physics. This being said I do know that CEMF produced by three separate windings (baring single phasing events) does indeed exhibit a relative 120 phase shift from one to another and CEMF magnitude is indeed roughly proportional to rotational speed. In later lectures on synchronous generators I'll demonstrate this effect using oscope traces.
@@bigbadtech Thanks, Jim.
Jim, why would the cemf be higher when the rpm is higher,but at higher rpm,rotor wires will cut less magnetic field since magnetic field is also rotating at higher rpm
The stator magnetic field remains fixed.
@@bigbadtech i was pertaining to squirrel cage Induction motors