What type of wire for dedicated 20A AC lines?

2x200W amp might take from mains close to 1kW during peaks. The problem is that peak supply current won’t be expected 8A, but rather close to 40A. It is because current is drawn only for very short time (millisecond pulse) at the peak of full wave rectified sinewave. It applies to most of LPS. Power delivered with such short pulses not only creates larger voltage drops in house wiring, but also heat-up amp’s power transformer, that has to be oversized (higher copper losses and higher core losses for eddy currents and hysteresis).

 

jea48 said:

Where was your reference point used for the measurement? At the electrical panel?

ieales response:

Where else?

Usually the no load voltage is checked at the last outlet on the branch circuit. No loads are connected to the circuit. If a difference of potential, voltage is present it will be the same as the applied voltage at the feed end. In this case the branch circuit breaker to neutral bar voltage.  If 120V at the panel it will measure 120V at the end of the branch circuit that has no load connected to it. (Add load and then measure again for VD.)

Why? Simple Ohms law. You need a load to have a VD. No load no VD. The internal resistance of a typical DMM is about 10M ohm. 

     jea48 said:

What type of volt meter did you use?

ieales response:

calibrated Fluke.

10M ohm internal resistance. 120V / 10M ohm = 0.000012 amp.

Jim

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@kijanki

+1

Please explain what happens if the power transformer’s secondary winding voltage is lower feeding the rectifier, due to a quick AC mains VD event, and the electrolytic capacitors voltage is higher. Just going from memory the rectifier will not conduct and the caps do not get recharged for that "(millisecond pulse)" in time.

Jim

I recently installed a dedicated 20 amp, 8 gauge multi-strand run.  The run is 123 feet in length first going to a 30 amp locking plug (that goes to my surge protector) within the entertainment console then an additional 2 feet to a pair of 20-amp, hospital-grade plugs at the termination outside of the console.

The 8-gauge wire is maintained all the way from the panel to the three outlets (including the hospital-grade recepticles) and there are no junction boxes along the way.

And just because I had it, I put a big ferrite bead over the wire where it comes out of the panel.

This cleaned up a bunch of "hash" on my Yamaha SACD, but less so on my Oppo95, which has a better power supply.

@jea48   You are right - there will be no current thru rectifiers until capacitor voltage will drop below rectifier supplied peak voltage.  Theoretically it is possible to build LPS where capacitors keep average instead of peak voltage, but it requires huge inductor in series (in order of Henries) made with thick wire and AFAIK nobody is doing it.  One problem is lower rail voltage (average instead of peak) while the other is dependency on the load current.

http://www.r-type.org/articles/art-144.htm