AVR wiring connection

[Thob]

BruceM,

Referring to the top diagram in Gary's post (fig 4), the main field appears to be connected to the brushes on the "D.C. Arm".  I believe this is 4 brushes that contact a segmented armature and provides the current to power the main field.  The variable resistor there adjusts the no load voltage.  These brushes appear to be wired in parallel, the two vertical bushes labelled "+" and the two horizontal brushes labelled "-".  These same brushes carry the current for starting (which also goes thru the series field winding), as well as provide current for charging the battery.  Note that starting the unit should provide an automatic field flash - the initial magnetic field to get things going.

The axillary field is connected in series with the load via the bridge rectifier.  This provides an increase in the field with increasing load current, which should help maintain a near constant voltage with varying load.  The "diverter" resistor bypasses some of the load current, thus provides adjustment for voltage at load.  Note that smaller resistance here provides for LESS boost at load.

[BruceM]

Thanks Thob! My mental fog cleared after reading your great circuit explanation.

So as Thob points out so clearly, adjusting the value of the "diverter" (shunt) resistor to a lower ohm value might be needed to get the full load voltage down to within tolerance at 60Hz.  Since the original designers chose to use a shunt resistance, I'd add one if there was none installed, instead of adding a series resistance.  If there was no "diverter" resistor present and I was forced to guess a value,  I'd start at a resistance to reduce the voltage by 1/3, or about double the auxiliary winding resistance.

I have high confidence of success with this minor modification for 60Hz operation of the SOM, now. 

[toastedsiopao]

Hi, just an additional question..

If I wanted to put a fuse in series with diode inputs or outputs, what will be the rating? I am using ST5, set at 220V. Thanks.

[mike90045]

Hi, just an additional question..

If I wanted to put a fuse in series with diode inputs or outputs, what will be the rating? I am using ST5, set at 220V. Thanks.

1A or 2A   I'd not bother. There is only a small winding that powers the diode bridge, which is only a $5 part. (OK, $2.69 if you buy on sale) The winding can only source a couple amps.  If something else shorts to it, frys the winding and the diode bridge, replacing $10 worth of 2A fuses is not going to help much.  And fuses are just more wires and stuff to vibrate, shake and break.

[Hugh Conway]

I was wondering if you can use a avr to boost my power from 50 on my english 6-1 start o matic lister 2.5 to 60 here in north americia as 50 does not work here with tvs and laptops . if someone that has tried one and a diagram. thanks.

I could be mistaken Rob, but I believe I learned elsewhere on the forum that  raising the Hz from 50 to 60 requires increasing speed of engine or generator via change of pulley size. That works on my gen set-up, though it is using a PMG. Hz varies directly with RPM. I have a SOM as well, but am not at a point where is is functional. I require 60Hz as well.

See the post by Listeroil about 1/3 way down the page. Lister used a different sized pulley to achieve 60Hz on the original SOM        http://listerengine.com/smf/index.php?topic=7079.0

Cheers,
Hugh

[dieselgman]

Absolutely right... the only way to change your output frequency on a given generator head is to change its speed. 1800rpm = 60Hz for any 4-pole head. There are some very expensive experiments with variable speed and fixed frequency electronics, but none that are viable at this time.

dieselgman