[MRCA] Hercules ZXB generator pt.2

[David Olean]

Hello Ray

That looks like an "old school regulator.  I never messed with them, but 
replaced them with newer electronic regulators. I think when the voltage 
increases, it drives a switch arm up and down that engages different 
power resistors (or resistance wire) that reduces the current to the 
field winding of the generator. The voltage drops a bit, and the wiper 
arm moves down to select a lower resistance and the field current goes 
up and raises the voltage. They looked "klunky" to me, so I replaced 
them with a Basler solid state regulator on an old genset I used to have 
from 1948-1952 vintage. It was a 10KW gasser with a 4 cyl 1800 rpm 
tractor engine.

In talking to the guy I bought the generator from, he said these old 
regulators worked pretty well, but you had to have clean contacts for 
them to work right.  The Basler had no switch contacts, so I went with that.

Right now I have an old Detroit 2-71 20KW diesel genset. It runs at 1200 
rpm and I think it has one of these old regulators in it. I never got 
into it, as my plans changed, but the unit is still in my shed!  It has 
never run since coming out of a telco central office.

If you are seeing 60 volts, that means that the field winding is getting 
low current and there is probably a bad connection in the switch 
contacts or maybe the arm is not moving. With low output voltage, that 
regulator would be pumping lots of DC current into the field winding. 
Something is preventing that. Do you see anything moving in the 
regulator? It may be stuck?

I had another diesel set, made for the Marines. It was also a Detroit 
2-71, but it ran at 1800 RPM and was 30 KW. My son said it sounded like 
a Boeing 707 landing in the backyard. It was very loud. It had a more 
modern speed regulator that sensed a magnetic signal off the flywheel, 
and the frequency of that signal adjusted the speed. It was designed 
before any modern transistors were in use, (1960's) so the throttle was 
pushed and pulled by a throttle control unit that ran off of fuel 
pressure generated by the fuel pump. I replaced that with a very cool 
modern solid state electronic speed regulator. It never varied no matter 
what! It was a beast, and kept the frequency spot on. The voltage 
regulator was a solid state design as well with a few 2N3055s 
controlling the field winding. I never dug into the voltage regulator 
because it always worked!

Dave K1WHS


On 4/12/2020 1:30 AM, Ray Fantini wrote:
>
> Ok, so I have been having an issue with the generator being its 
> voltage regulating system doesn’t work. Understand that frequency 
> control is maintained by the mechanical governor and that’s right on 
> at 60 cycles @ 1800 RPM but the issue is voltage control.
>
> If I run the generator in manual voltage control can use the rheostat 
> on the control panel to control output voltage but when I switch it to 
> automatic the output drops way down to sixty volts.
>
> I have mentioned before that the voltage control is thru some very 
> strange looking device. Discovered today that the “thing “is a Ward 
> Leonard 5660 voltage regulator. Removed its protective cover and 
> inside is two huge multi tap ceramic resistors on each side and 
> something that looks like a relay in the center that has a twisted bar 
> that appears to vary a rolling carbon bar across a dual set of very 
> strange looking coil contacts.
>
> I did clean it all up and also cleaned the high wattage variable 
> resistor in series with it but did not have time to put it all back 
> together and test run it to see if it works.
>
> Did a quick internet search and Ward Leonard is still in business and 
> was a leader in developing motor speed and control systems from back 
> as far as 1890
>
> I am including a picture of this strange looking device in case there 
> is someone out there who can explain how this thing works. And yes I 
> know it varies the field voltage but just how dose it function?
>
> Ray F/KA3EKH
>
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