[ARC5] Power supply suggestions

[Paul H. Anderson]

Howdy all,

I just did some experiments tonight with some equipment.

I used one radio, a BC-453-B with some modifications, and tried three
different dynometers on it, the first was a DY-2/ARR-2, which with the
radio drew 1.1A steady state.  The second two were DM-32A, one with bad
bearings (dry), the second had not been run by me, and maybe had not run
for a long time.  Those two ran around 1.4A steady state.

Using my adjustable Lambda lab power supply, I set the voltage to 28V and
the current limiter to 1.5A.  This was not enough to start the dyno.  
Setting it to 2.75A, it had no problem starting two of the dynos, but
struggled a bit on one (the one I never ran before).  None of them started
quickly, however (in the sense of jerking on the rubber bushing mount).

My fixed voltage Lambda, a LM E28 rated at 10A, 28V +/- 10%, starts the
dynos with no hesitation (slight jerk or visible twitch in the dyno as the
torque comes on).

The DY-2 is rated at 1.1A continuous, and the DM-32A is 1.4A continuous.  
(I didn't examine the equipment closely to make sure tags hadn't been
swapped, or dynos on different bases, or whatnot).

I think that 5A would "work" but be a bit risky - or at least you'd want
to be quite careful to make sure it really started up - you can smoke the
brushes if the motor isn't turning, I believe.

10A appears quite adequate for a single receiver and dyno.  It may also
work for multiple receivers and dynos, especially if one didn't turn them
all on at once.

If it takes more than this, something is wrong and needs attention, in my
opinion.

The Lambda power supplies have a voltage sensing feedback loop - it will
try and drive to 28V, up to the limit of 10A (or whatever the unit
specifies), at which point the voltage will drop.  I don't know that all
of them have this, but the numerous ones I've looked at do.

Don't get me wrong, I'd love a big 28V supply - I've been interested for
awhile in a T-195, which does need a beefy one (I don't think 50A is
enough, though).  Maybe someday... gotta keep the peace in the
household...

Paul

On Wed, 16 Jan 2002, Ray Robinson wrote:

> 
> Hi there,
> 
> Fair Radio has/had a large miltary supply 28v/50A,
> just forget the number at the moment.
> It is a switcher (SCRs rather than transistors), but a large
> capacitor on the output.
...> 
> regards
> ray vk2ilv