Muller Dynamo

[bolt]

Either you are replicating OR you are up-scaling and using bigger better coils and magnets. In which case get the best Schottky diodes you can afford. Excess amps now wont go a miss later. With 10A diodes in a bridge you got like an easy 50w per coil with 10 very large generator coils collectively 500w system.

Is this what you are building?

Also one other point. Once you built this some of you will want to use coil shorting to give an extreme boost of power and volts. You get 300-400v when the coil is shorted. If you plan on doing this you need like 500v diodes. At 350v and 0.5 amp you now have 175 watt per coil = 1.7Kw system. No its not too far fetched the wind power guys make these muller style systems at that power rating.

[hoptoad]

Now that I think about the current rating suggested I'm wondering if you knew I was planning these for each coil (using 4 as FWBR) as the current rating seems higher than what I would have imagined.  But I'm mostly guessing and I know you understand this better but my plan for these is not at the output of all coils just for each one.  Knowing that RomeroUK's 1N4007's are only rated 1.0 amp does it sound right to need 12 amp?  Although I'm not sure what his FWBR's current rating was he paralled these on so .... I'm lost in the Amperage jungle.  lol

Most of the time the old adage, bigger is better is true LOL.

After all, a higher current rated diode will withstand a greater current than a lower one and therefore is less likely to be damaged, when and if, a large transient current spike occurs during operation.

The main difference in a diode's performance in a given circuit is not so much their power rating (if it is not exceeded), but their forward voltage threshold.

The forward voltage threshold will determine the power loss within the diode. The higher the threshold the greater the loss.

To give an (approximate values) example:

A. Silicon power diode: = .6 V forward voltage = .6 V  multiplied by X amount current = .6X power loss
B. Germanium power diode: = .4 V forward voltage = .4 V  multiplied by X amount current = .4X power loss


Cheers

[nul-points]

Now that I think about the current rating suggested I'm wondering if you knew I was planning these for each coil (using 4 as FWBR) as the current rating seems higher than what I would have imagined.
[...]

hi e2m

i'm no guru here, sadly!

as mentioned above, this part was the nearest one i could find at Farnell at the moment, with a current rating  above the sort of current being handled in Romero's circuit

i mentioned looking for a lower rating (eg. 6A) in your usual suppliers (eg., Digikey, perhaps, in the US?) which should still give plenty safety margin

my very approximate estimate of Romero's system was that it's operating around the 50 Watt level (including motor + spare capacity for load)

it might appear that it's possible just to divide the current rating between the generator coils

whilst it's true that there is overlap between coil outputs, each coil could be capable of providing several amps at full load

at the moment we don't have too much detail of the performance data for the system

a couple of members have suggested that some more comprehensive load tests be carried out to 'characterise' the device's generating capacity

until we have more info, i'd suggest the minimum current rating needs to be in the region of at least 5-6A so that the diodes aren't being operated near their limit

hope this helps
np


http://docsfreelunch.blogspot.com

[Mem]

Hi Romero.

I've noticed from the schematic of your circuit that you are not directly taking advantage
of the collapsing magnetic field of your drive coils when thay are in off mode.

Now there may be a good reason for this, as the introduction of feedback diodes to collect power
from the drive coils during the collapsing field event, may significantly alter the tuning of the machine. ??

But, then again, maybe you haven't tried this ??
If you have'nt already tried this, then perhaps you'd like to.

If your current operating duty cycle (on time) is lower than 30 %, then there is a very high probability that adding feedback diodes and a battery to collect the CEMF may also result in an increase in total motor torque - free of charge. This in turn may increase your total output from the gen coils?

It's an easy experiment for you to try, as it requires no tricky changes to any aspect of your current build.

Just a couple of diodes and a battery hooked up the way I've shown in a modified version of your schematic attached below ..... Perhaps you've already tried this.?

I am very curious to know how this slight addition will affect your setup. Thanks in advance if
you choose to experiment and report on the result. Understanding, if not.

Cheers from Hoptoad ..... KneeDeep

Your idea is good. However, these is no battery in the circuit so why bother charging a battery?  But, yes collecting the  back emf from driver transistors can cool the off. It's may be an optional idea that can be useful.

[toranarod]

while we are on the subject of coils
I have a come up with this. here is a 15 mm litz wire coil on a ferrite former.
what is the inductance of the coils in RomeroUK motor? any body have even a close idea?