Kevin Weddle Posted April 4, 2007 Report Share Posted April 4, 2007 Does current that is out of phase with voltage mean lower available power. I see inductors used everywhere in power supplies, but are they used for more than ripple reduction? Quote Link to comment Share on other sites More sharing options...
audioguru Posted April 5, 2007 Report Share Posted April 5, 2007 Power supplies are usually DC and use a big filter capacitor or an inductor in series with the filter capacitor to block AC with the inductor and short the AC to ground with the capacitor to smooth the rectifier pulses. The resistance of the inductor reduces the output current available from the power supply.DC doesn't have phase relashionships. AC signals do. Quote Link to comment Share on other sites More sharing options...
Gazza Posted April 5, 2007 Report Share Posted April 5, 2007 Does current that is out of phase with voltage mean lower available power. I see inductors used everywhere in power supplies, but are they used for more than ripple reduction?It is all about the Power Triangle. So the answer is, it depends on what you mean by power. If the current and voltage are in phase, all of the power will be "real" so real power = apparent power or KW = KVA.If there is an inductor or a capacitor in the circuit, the voltage and current will be out of phase, therefore the real power will be the same but there will be a component of "active" power which has a phasor +/- 90 degrees out of phase with the real power. When you determine the "apparent Power" it will now be more than the "real" power or KVA>KWThe long story short is study the power triangle.Audioguru, there are many types of AC power supplies, what about a UPS or a VFD? Quote Link to comment Share on other sites More sharing options...
audioguru Posted April 5, 2007 Report Share Posted April 5, 2007 I don't think an inductor reduces ripple in an AC power supply unless it is a PWM circuit. Then the series inductor blocks the high frequency but passes the lower frequency modulation. Quote Link to comment Share on other sites More sharing options...
indulis Posted April 5, 2007 Report Share Posted April 5, 2007 There are different "kinds" of power Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted April 5, 2007 Author Report Share Posted April 5, 2007 Is there any relevance to this concept? I use reactance for phase calculation, and I can't think of where the current/voltage phase relationship is ever used. I just figured that if I had a capacitor in an AC power application, I could add an inductor somewhere and get more power. Maybe that's why motors have capacitors. Quote Link to comment Share on other sites More sharing options...
indulis Posted April 6, 2007 Report Share Posted April 6, 2007 The capacitor in a "capacitor start motor" is only there to "start" the motor Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted April 6, 2007 Author Report Share Posted April 6, 2007 If your using a power source, like the secondary of a transfomer to run the motor, why do need a start capacitor? The power source has enough power. Quote Link to comment Share on other sites More sharing options...
pzilla Posted April 12, 2007 Report Share Posted April 12, 2007 The capacitor in a "capacitor start motor" is only there to "start" the motor Quote Link to comment Share on other sites More sharing options...
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