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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Lets say I have a single layer air core coil, connected to a LC tuned circuit. Is there a formula I can use to calculate the voltage (or volt per turn) distribution along the length of the coil?
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
If the length of wire used to make the coil is much less than 1/4 wavelength then the volts/turn is linear. As the length of wire approaches 1/4 wavelength a more sinusoidal volts/turn along the length will arise and need modeling.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
It's my understanding that the flux density decreases near the ends of the coil, as some of the flux "escapes" in between the turns, especially with long coils. So I would think that the distribution won't be linear even at frequencies much lower than the 1/4 wavelength, but please correct me if I'm wrong... I need to know this in order to know where to tap a coil in a tuned circuit to get the required grid drive for a tube (which is just a small percentage of the total voltage across the coil).
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
If is a series resonant LC circuit there will be current which is controlled by the Q of the coil.
Lets say it is 1 ampere at 10 kHz, and the total inductance is 10 mHy. At your tap, you could consider there is two coils in series. The two coils are L1 + L2 + 2Lm = 10 mHy. 2Lm is found by measuring each of the two coil segments alone, and subtracting their sum from 100 mHy. If you know the inductance from the bottom to the tap, then you know the voltage by I*6.28*1E5*L
Would a tap at 1/10 the length from the bottom give about 70 volts ?
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Air coil voltage distribution
