Pierre's 170W in 1600W out Looped Very impressive Build continued & moderated

[seaad]

Hi Seead,
At such a low clock frequency DC resistance dominates so..
L192

Hi L192
Your coil: About 1.2mH (free)  assuming 2.5 mH (tight to secondary core)
1.2mH => XL 60Hz ==> about 0.5 Ohm
2.5mH => XL 60Hz ==> about 1 Ohm
Roughly;  DC flows half the time of the outgoing frequency (60Hz; 8.3ms) then DC in the opposite direction next half, if looking at one single coil.

Pic : one single coil Z (Roughly)

Regards Arne

[listener191]

IRF3205 / IRF4905

Max values
55V, 200W, continuous Id=52A/80A, Pulsed I=260A/390,  Rds(on)  8mOhm/20mOm

An interesting mosfet matching and cheap. With a capable heatsink it will run fine

http://www.irf.com/product-info/datasheets/data/irf3205.pdf
https://www.infineon.com/dgdl/irf4905.pdf?fileId=5546d462533600a4015355e32165197c

As for clamping diodes i was thinking about UF5408. 1000V/3A. Any other idea here?

Hi Jeg,

Whats wrong with using the body diodes, or are you concerned about heat?

Regards

L192

[listener191]

Hi L192
Your coil: About 1.2mH (free)  assuming 2.5 mH (tight to secondary core)
1.2mH => XL 60Hz ==> about 0.5 Ohm
2.5mH => XL 60Hz ==> about 1 Ohm
Roughly;  DC flows half the time of the outgoing frequency (60Hz; 8.3ms) then DC in the opposite direction next half, if looking at one single coil.

Pic : one single coil Z (Roughly)

Regards Arne

Hi Seaad

Except if I clock at 60Hz then current reduces. Clocking at 20 to 25Hz produces the largest output.

Also even if I take your impedance example for a single coil, I have 6 in series (under test), =8.4 ohms.

I have been operating at 35V so 35/8.4= 4.1A.

4.1A is achievable at 20Hz clock rate, not 60Hz.

Regards

L192 

[seaad]

Hi Seaad
A) Clocking at 20 to 25Hz produces the largets output.

Also even if I take your impedance example for a single coil, I have 6 in series (under test), =8.4 ohms.
I have been operating at 35V so 35/8.4= 4.1A.
B) 4.1A is achievable at 20Hz clock rate, not 60Hz.
L192

A) Pierres freq. 13-15 Hz 

B) You have a multiplicative effect with the (total 6 coils) m-Henry value due to overlapping coils and some weird half and full transformer function depending of the proximity to to the output core. Due to that the Z goes up steeper than just adding coils. A higher total Henry value favorably even at 20 Hz.

Which inductance value do you get to a 6 coil overlapped "section"? Away or close to the output core.

Regards Arne

[listener191]

A) Pierres freq. 13-15 Hz 

B) You have a multiplicative effect with the (total 6 coils) m-Henry value due to overlapping coils and some weird half and full transformer function depending of the proximity to to the output core. Due to that the Z goes up steeper than just adding coils. A higher total Henry value favorably even at 20 Hz.

Which inductance value do you get to a 6 coil overlapped "section"? Away or close to the output core.

Regards Arne

Hi Seaad,

With the rotor open circuit and rotated through 360 degs, the minimum inductance of 6 coils in series is 9.7mH  and the maximum inductance is 98mH.

There is nothing particularly strange about the windings, apart from the linear distribution that produces a triangular wave.
The individual coils flux add, with the peak half way between the start of the first coil and the end of the 6th coil.

For a distributed winding to produce a sine wave, a gap is needed between the coils so the flux rise rate reduces towards the peak.

Regards
L192