[ARC5] Dynamotor Regulation

[David Stinson]

The problem is not the running-current of the dynos.
The problem is the mighty surge-current it takes to start them.
The start-up surge for the Hulk-o-Motor that runs my BC-375
is about 75 Amps.... OWWWW
Batteries across the supply was the answer for that one.

However, my entire 2TX-3RX SCR-274N runs well from
a power supply half the size of a shoe box and with a 
couple of large caps across it to help with dyno surge currents.
It's an Aztec switching supply.  Had no trouble with birdies
so far; perhaps they're all outside the bands in question.
Will take some photos later today when I can get out to the barn.

I had a larger switcher and a big bank of capacitors that
would start the BC-375 Hulk-o-Motor, barely.  But that switcher
was a bit noisy and I had the batteries to so went that way.

I have a Godzilla-Motor by RCA that runs on 12V and 
outputs 1500 for some 1930s RCA aircraft rig.
It's the size of a gallon milk jug.
Starting that one is going to be an adventure.

73 DE Dave AB5S




-----Original Message-----
From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
Behalf Of Craig
Subject: Re: [ARC5] Dynamotor Regulation


I took a run thru T.O. 12R2-3SCR274-2 ( used to be 16-40SCR274-5). From
Table 2, page 63,  it shows worst case current draw is at 28 VDC, 4
transmitters, 3 receivers all powered, with 1 transmitter operating in CW
mode. Current draw is 15.6 amps +/-10%. From Table 18 in the same
publication, a DM-32 will draw 1.1 amps at 28 VDC, continuous operation,
while a DM-33 draws 5 amps continuous and can surge to 7 amps under
intermittent conditions.