I can't replicate the post #35 results. I'm seeing an average dissipation of ~60W in the Darlington at high reves, with L1 resistance = 2 Ohms. What resistance did you assume for L1?
It would help if you assigned labels to each node that so that we know which waveforms you're plotting, and if each time you change the circuit you post the new .asc file.

No. Incandescent lamps have thermal inertia and "see" the RMS voltage.

I am sorry, I forgot to attach the .asc file. Here you go..
Yes, L1 has 2Ω.

 

I built the design at post #35 with D1/2/3/4 = 1N5403 and transistor TIP122.
The output was perfect, but
D4 =====> Hot
Zener ===> Very Hot
TIP122 ==> Very Hot (perhaps it is reaching its rated power dissipation limit)

 

All of D1/2/3/4 should be equally hot, dissipating ~1.7W average each at high rpm.
There's something wrong if the zener is getting hot. According to your sim it should be dissipating less than 10mW.
The TIP122 should be the hottest of all, dissipating ~53W average at high rpm.

All of these figures are based on assumptions about the generator coil resistance, inductance and output voltages, which may differ dramatically from the real world.
Do you have figures for the coil's actual resistance and inductance? Those values are surprisingly hard to track down on the web. It's as though the automotive geeks have no electronics knowledge and the electronics geeks have no automotive knowledge .

 

Your Theory circuit and the Real circuit are obviously two different ones, as they are not giving the desired results!!

 

Do you have figures for the coil's actual resistance and inductance? Those values are surprisingly hard to track down on the web. It's as though the automotive geeks have no electronics knowledge and the electronics geeks have no automotive knowledge

No, I do not have those figures. The resistance can be measured with a DMM, but the inductance might be little difficult until I open the magneto.

 

I managed to measure the resistance and the inductance of the generator coil, which are 1.2Ω and 1.635mH.

Today, I built this design (the asc file is attached)


and got these results:

Without load 6V rms at idle and 8V rms at 6000RPM. (Zener is 12V)
With lights on 5V rms at idle and 7.5V rms at 6000RPM.
The SCR was hot.

Here is a photo of the regulators I am talking about.

The Chinese unit has a cavity of 36x31x15mm for the PCB whereas the OEM unit has 30x18x15mm. Both units barely get warm on operation. I have built the Chinese circuit which works fine, but according to my experience they are not reliable because they fail after sometime. I am looking to build something reliable like the OEM which has definitely very few components. I failed to rip off the OEM but was successful enough to find two SCRs BT151 which were not even attached to the body (means they didn’t required heatsink).

The two BT151 in the OEM hints me to use two SCRs in parallel to share the heat dissipation.

 

I managed to measure the resistance and the inductance of the generator coil, which are 1.2Ω and 1.635mH.

Good. Worth knowing for future reference.

 

Additionally, please guide me ...... I am bit confused over the Average and RMS voltages in the simulation. I cannot judge if the simulation results are ok or not. For 12V bulbs what should me my target voltages for Average and RMS?

 

Think of it this way. A pure AC sine-wave has an average voltage of zero (each positive half wave is cancelled by the following negative half-wave). Nevertheless, each half cycle is capable of causing non-zero heating in a resistor. The RMS (root mean square) voltage is the value of a notional DC voltage which would give the same heating effect.
Of course, the generator output is probably some way removed from being a pure sine-wave, depending on the geometry of the coil pole pieces and the magnets in the flywheel.
Since an incandescent bulb filament is predominantly a heated resistor, the relevant voltage value is the RMS one. You're aiming for 12V RMS.

 

Thanks Alec, that was really helpful.

Any comments, why the output of the physical circuit at #46 is 7.5V in contrast with the simulation?
Swaping the zener and the resistor only eliminates the negative cycle.
Increasing the zener value to 15V slightly increase the output RMS from 10.46 to 10.8V.
I shall be grateful for helping me achieve the targeted 12-14V RMS.

 

I also have this design in waiting to try

 

Any comments, why the output of the physical circuit at #46 is 7.5V in contrast with the simulation?

What are you using to measure the "RMS" voltages? As I think I mentioned, a DMM will probably lie if the waveform isn't a pure sine-wave.

 

What are you using to measure the "RMS" voltages?

A moving coil multimeter.

 

Today I build a fresh circuit as per post #46, swapping the positions of the resistor and zener.
Same result -------------- 5V at idle and 7V at 6000RPM with lamps on.

 

Can't see how the thyristor is getting a gate pulse with the zener tied to the Cathode, it should be at the Anode...

 

Can't see how the thyristor is getting a gate pulse when the zener tied to the Cathode, it should be at the Anode...

The voltage at the junction of resistor and the zener to be measured against the negative of the bridge rectifier.
Besides, I have already tested the same circuit by swapping the positions of the resistor and the zener but the result is unchanged.

 

Failing to get the desired results from any of the discussed circuits I decided to focus on the Chinese design. The schematic is as below:



The actual circuit is built with SMD components. D1-D4 is 0.5A bridge, the transistor is 2L (150V/500mA) and zener Z6 (7.5V). The performance is 7V rms at idle and 12.5V rms at 6000RPM with lights on. The SCR remain at ambient temperature.

I replicate this circuit with thru-hole components using:
4 x 1N4148 for D1-D4, BC558 for Q1, 3.9K for R1, 10K for R2 and BT152 for the SCR.
For 1 or 2 days, it performed as per original circuit. Then suddenly BT152 started getting hot.
I doubted BC558 because it is fairly low rated (30V/200mA) and also D1-D4 (1N4148) which are also rated 200mA.
I built a fresh circuit using 1N4007 for D1-D4 and 2N5400 (120V/600mA) for Q1. But again the BT152 is getting hot.

Could the values of R1 and R2 be crucial? I think BT152 (20A) should do fine instead of BT151 (12A); actually I have no BT151 with me and have about 10-15pcs of BT152. Or could there be any other factor which is making the SCR hot?

 

Could the values of R1 and R2 be crucial?

I don't see why they'd be crucial unless changed dramatically. You can easily play with values in LTspice to see the effect.