Question for Dave Mac
02-13-2004, 08:52 PM
#1
1000 Watt CAFz'r
Thread Starter
Join Date: Oct 2003
Posts: 1,783
A while ago you brought up the theory of voltage leading current...or current lagging behind voltage. I'm interested in it, but don't know jack about where to get info on this kind of theory. Is there anything you'd recomend to read?
Thanks,
Adam
Thanks,
Adam
02-14-2004, 08:09 AM
#2
Guest
Posts: n/a
While I'm not Dave.... 
Read up on AC power transmission, Power Factor, and Hysteresis and you'll get a pretty good idea of what happens and potentially how it relates to audio.
Honestly - pick up a first year Physics text that a good tech school uses. They may cover it in there (although not in great detail) as well as a ton of other neat stuff. That goes for any reader here.
Read up on AC power transmission, Power Factor, and Hysteresis and you'll get a pretty good idea of what happens and potentially how it relates to audio.
Honestly - pick up a first year Physics text that a good tech school uses. They may cover it in there (although not in great detail) as well as a ton of other neat stuff. That goes for any reader here.
02-14-2004, 08:35 AM
#3
Yankee
Join Date: Oct 2003
Posts: 3,599
Basic AC electrical theory:
In an inductive circuit Voltage leads current
In a capacitive circuit current leads voltage
In a resistive circuit voltage and current are in unity
Any book on electrical treory (older ones are written clearer in my opinion) I have used 'Alternating and Direct current', 'Electrical design for radio engineers'and there are loads in your local bookstore or on Amazon.com.
In an inductive circuit Voltage leads current
In a capacitive circuit current leads voltage
In a resistive circuit voltage and current are in unity
Any book on electrical treory (older ones are written clearer in my opinion) I have used 'Alternating and Direct current', 'Electrical design for radio engineers'and there are loads in your local bookstore or on Amazon.com.
02-14-2004, 10:44 AM
#7
Guest
Posts: n/a
In a purely inductive load (ie coil) the current will lag voltage by 90 degrees.
Now if you add resistance in there it will change the angle closer to unity.
The simplest way to understand it to use a right angle impedance triangle, resistance being the adjacent side (P), inductive reactance (inductance from coil) being the opposite side (Q) and Impedance being the hypotenuse (Z)
To figure out impedance (Z) use Pythageris theorim A^2+B^2=C^2 so resistance (P) squared + inductive reactance squared (Q) = the square root of Impedance (Z)
The angle in your triangle (P/Z )is how far behind the current lags voltage. To find the value of current divide E (voltage) by Z (impedance)=I (current)
You end up with 4A @ 35 degrees lag as an example.
Capacitance works the same, only it leads voltage, if you have both in a circut the will cancel each other out if they have the same value.
Hope this helps somewhat...
Now if you add resistance in there it will change the angle closer to unity.
The simplest way to understand it to use a right angle impedance triangle, resistance being the adjacent side (P), inductive reactance (inductance from coil) being the opposite side (Q) and Impedance being the hypotenuse (Z)
To figure out impedance (Z) use Pythageris theorim A^2+B^2=C^2 so resistance (P) squared + inductive reactance squared (Q) = the square root of Impedance (Z)
The angle in your triangle (P/Z )is how far behind the current lags voltage. To find the value of current divide E (voltage) by Z (impedance)=I (current)
You end up with 4A @ 35 degrees lag as an example.
Capacitance works the same, only it leads voltage, if you have both in a circut the will cancel each other out if they have the same value.
Hope this helps somewhat...
02-14-2004, 11:57 AM
#9
Guest
Posts: n/a
Shoulda cleared that up a little...powerfactor (1 is unity) is equal to P/Z, the inverse cosign (cos-1) of the powerfactor is your angle.
It's just basic Trig, you can perform the functions however you want, I found this way the easiest.
[ February 14, 2004, 01:04 PM: Message edited by: Kilowatt ]
It's just basic Trig, you can perform the functions however you want, I found this way the easiest.
[ February 14, 2004, 01:04 PM: Message edited by: Kilowatt ]
