# Single conductor inside hollow conductor

1. ## Re: Single conductor inside hollow conductor

50 Hz is way too low for 13 turns on an unknown core size

for ferrite Bpk < 0.3T Bpk = Erms /( 4.44 F. N Ae ) for sine wave. Ae = ferrite core area, N = turns, F = Hz

- - - Updated - - -

area in m^2

1 members found this post helpful.

•

2. ## Re: Single conductor inside hollow conductor

It makes sense to characterize the transformer in terms of mains and leakage inductance plus large signal parameters.

In case of 50 Hz application, leakage inductance can be effectively neglected, but main inductance respectively magnetizing current can't. The voltage drop you are seeing isn't caused by insufficient coupling but voltage drop due to magnetizing current. It would be roughly the same with regular transformer windings and same number of turns.

1 members found this post helpful.

•

3. ## Re: Single conductor inside hollow conductor

13 Turns on a steel core will give you a much better indication @ 50Hz

•

4. ## Re: Single conductor inside hollow conductor

Originally Posted by Easy peasy
13 Turns on a steel core will give you a much better indication @ 50Hz
The core I used is hitachi amcc100. I mistakenly said that it was 13 turns on core. I initially had 6 turns on core and was seeing the lower voltage. When I went to 13 turns the coupling was much better. In both cases the current was higher when voltage was applied to outer conductor. My apologies for the misinformation. I work away from home 4 weeks at a time and trying to recall things from memory. When I get back home I will take measurements again and post them.

5. ## Re: Single conductor inside hollow conductor

I applied 3 vac across center conductor and measured 1.4 vac on shield wire. When I applied 3 volts to shield wire I measure 2.71 volts on center conductor.
I do not have any direct explanation but these come to the mind:

1. The two conductors are not symmetrically places. Because the shield is floating, a large part of the electric field is blocked and a smaller part of the magnetic field is also blocked (more if the shield is solid). That I guess is the reason for case I. Correct way, in my opinion, is to twist two coaxes nicely, connect the shields to the ground (fixed voltage) and measure the effects between two core conductors. There are coaxes with foil shields and they may be used for more reliable results.

2. When the shield is used a primary, the electric field will be zero inside but the magnetic field will be not. But because of the gap (there will be some space), we shall have some leakage. Hence I expect higher voltage for case II.

You should carry out the experiment (i) without a core and (ii) with a simple rod (iron or ferrite) whose length is larger than the coil length.

3. By the way, did you measure the current?

1 members found this post helpful.

•

6. ## Re: Single conductor inside hollow conductor

if anyone wishes to continue he discussion of potential, emf and voltage, etc,