dc amps vs ac amps

[outback]

what is the differece between ac and dc amps win measuring it? and how do i measure it to determine what my genny is putting out?

[LEXX]

DC Amps and AC amps are the exact same thing, they are the measurement of electrons past a given point, the difference is that the electrons of AC go back and forth (alternating) and DC go only in one direction (direct).  Measurement must however be done with two different meters, if you measure AC with a DC ammeter it will twitch a lot but you'll get no reading, if you measure DC with an AC ammeter it might just let it's magic blue smoke loose and you will have a nice christmas tree ornament but no more ammeter.  I imagine you have your genny hooked up to a rectifier then to a battery?  If so, after the rectifier you should hook your DC ammeter up in series (one wire to the positive post of your meter from the positive post of your rectifier, the other wire to the negative post of your battery from your negative postof the ammeter or vise versa depending on the set-up), with the reading you get you should be able to just multiply the amps times the voltage of your battery and you will get total watts.  If you aren't hooked up to a battery you can hook up your genny before before the rectifier to an AC ammeter and give it a spin, polarity doen't chane a thing, the problem witht this is that the amperage you get will be the short-out amperage and not an actual amperage of your specific genny on the pole, it will also be fairly hard to spin.  You can get voltage tho.

Hope that helps,

LEXX

[bill541]

"one wire to the positive post of your meter from the positive post of your rectifier, the other wire to the negative post of your battery from your negative post of the ammeter or vise versa depending on the set-up"

I think what Lexx meant to say was positive post of meter to positive post of rectifier and negative post of meter to positive post of battery.

Lexx is correct by saying you want a series circuit when measuring current. An easy way to think about it is to remove a wire from the circuit and replace it with the ammeter leads.

The reason most people measure the DC output of the rectifier instead of the AC input is that you need a true RMS meter to measure the AC current of a 3-phase machine accurately.

A less expensive meter can be used to measure AC current in a single phase system as long as the output is a clean sinewave. Most of these meters are adjusted to read a sine wave OK.

-Bill-

[LEXX]

Good eye Bill, I almost gave him a bum steer there!

LEXX

[scoraigwind]

It depends if you are single phase or 3-phase.

In the case of single phase then the battery charge current will be the average of the AC current.  This could be as little as half of the rms current.

If we look at 3-phase then the rms is below the DC.  Rms will be between 70 and 82% of the DC output.

It's generally simpler to measure DC if that's what you want.  You can use a multimeter set to millivolts and measure teh coltage across a length of wire to the battery and get fairly good results.  Of course it needs to be calibrated and you have to prevent the wire from getting hot or it reads high.  It's a good idea to use thick wires anyway!

[outback]

thanks for the help everyone.Hugh has kind of lost me tho on the 70 to 82% rms thing. but thanks again.

[LEXX]

And the coltage as well, is that a fancy word for horsepower?  Just kidding Hugh, by the way good books, when are you coming out with a new one?

LEXX