Some tests on mono and bifilar coils

[synchro1]

The "Old Scientist" measures one half the resistance 5.86 Ohms in his series bifilar solenoid compared to the single wire solenoid of same wire length and gauge at 11 Ohms. I don't understand why you indicate the same resistance in both types of coil wraps in contradiction to the "Old Scientisit's" measurements, or am I missing something? The disappearance of half the Ohmic resistance in Tesla's SBC amounts to a deep mystery to me. Haven't you tested for this difference yet?



http://www.youtube.com/watch?v=uNAZ6heorEc&list=UUNbdkwT-LstmshlLDOqs7JA

[conradelektro]

I did a "speed up under load" experiment with the monofilar coil

(because my last speed up experiment was done with an old bifilar coil, see my video http://www.youtube.com/watch?v=vAXQBpuLu68).

It would be nice of the experts to verify my power dissipation calculations (see the scope shot and the calculation on the attached drawing). I did the calculation as Gyula showed in his post http://www.overunity.com/14235/some-tests-on-mono-and-bifilar-coils/msg385763/#msg385763.


Calculation also here:

monofilar coil (DC resistance 77 Ohm, Ferrite core)

no load, resonance at 90 Hz rotor speed, motor power consumption 5.4 V and 1.12 A
dissipation in LC circuit: 0.148 * 0.148 * 77 = 1.68 Watt   
(motor needs 5,4 * 1.12 = 6.04 Watt)


85 Ohm load, 98 Hz rotor speed, motor power consumption 5.4 V and 0.81 A
dissipation in LC circuit: 0.06 * 0.06 * 77 = 0.27 Watt 
dissipation in 85 Ohm load: (4.8 / 85) * 4.8 = 0.27 Watt
in sum 0.54 Watt
(motor needs 5.4 * 0.81 = 4.37 Watt)

If the load is around 80 Ohm the power dissipation in the LC circuit and in the load seem to be about equal (at least at 98 Hz rotor speed).

Greetings, Conrad

[Farmhand]

Conrad, you could maybe check the output impedance of the coil using the Thevenin Theorem. It's not as complicated as it looks.
Thevenin's Theorem
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/acthev.html#c1

Simply note the output open circuit voltage then short the output and measure the current through the coil. Then divide the open circuit voltage by the current and it tells us the output "impedance" in Ohms.

Going by your results the output impedance should be about 80 Ohms. The output impedance consists of both the DC resistance and the AC reactance.

Calculations look good to me but I'm no expert. 

Cheers

[conradelektro]

Conrad, you could maybe check the output impedance of the coil using the Thevenin Theorem. It's not as complicated as it looks.
Thevenin's Theorem
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/acthev.html#c1

Simply note the output open circuit voltage then short the output and measure the current through the coil. Then divide the open circuit voltage by the current and it tells us the output "impedance" in Ohms.

Going by your results the output impedance should be about 80 Ohms. The output impedance consists of both the DC resistance and the AC reactance.

Calculations look good to me but I'm no expert. 

Cheers

@Farmhand: Thank you for looking up Thevenin's Theorem. You can see the "open circuit Voltage" on the scope shot on the left in my last post, it is 25,6 Volt (true rms, at the resonance situation with 90 Hz rotor speed).

I just measured the current through the 1 Ohm resistor if I shorten the output; it is 60 mA (speed goes to 98 Hz).

The Thevenin's Theorem calculation: 25.6 / 0.06 = 426 Ohm


Now, I put a 420 Ohm load resistor (1 K pot, 4 Watt) at the output and the situation is a s follows:

speed goes to 95 Hz, see the attached scope shot, circuit as in my last post

Dissipation in the LC circuit:  0.088 * 0.088 * 77 = 0.59 Watt

Dissipation in the load: (13.6 / 420) * 13.6 =  0.44 Watt (motor needs 5.4 V * 0.97 A = 5.2 Watt)

Well, the situation with a 420 Ohm load seems to be better than with a 85 Ohm load: the total output rose to 1.03 Watt (but there was also more load on the motor)

85 Ohm load:  total power dissipation 0.27 + 0.27 = 0.54 Watt (motor needs 4.37 Watt)

420 Ohm load: total power dissipation 0.59 + 0.44 = 1.03 Watt (motor needs 5.2 Watt)


Just to clarify, all measurements and tests are done like this:

- I set the power supply to 5.4 Volt which causes the rotor to turn at 90 Hz (148 mV over 1 Ohm shunt, 25.6 Volt over coil or 10 µF cap)

- then I shorten the output (60 mV over 1 Ohm shunt)

- or I put a 85 Ohm load resistor over the output (60 mV over 1 Ohm shunt, 4.8 Volt over 85 Ohm load)

- or I put a 420 Ohm load resistor over the output (88 mV over 1 Ohm shunt, 13.6 V over 420 Ohm load)

Greetings, Conrad

[Farmhand]

Well the theorem seems to hold, it can tell us what resistance will show the most power for a given coil at a certain frequency. if the speed changes during tests and so forth (unlike a wall transformer) then some tuning would be needed, but the Theorem can guide us to max power output maybe. Interesting.

Cheers