I managed to find about 14uF worth of non-polarised capacitors, so
cobbled them all together and connected them across the CW and CCW
leads.
That's probably not enough to be significant.
From an HVAC blog I found a formula for determining the value of a
run capacitor (note the HVAC folks deal with much higher voltages
and currents!). The formula they give is: C(uF) = (2652 * I)/V
where I is current through the capacitor and V voltage across the
capacitor.
In both the Emotator and CDE/HyGain cases, the common motor current
is about 2 A (1A in each winding) or about 1A through the cap (Hy-Gain
is specified at 24VAC/2.25A). Using the Hy-Gain numbers which are
consistent with Emotator's 70 VA rating that works out to 125 uF.
The 100 uF Emotator cap may be a bit undersized while the CDE/HyGain
130-156 uF cap may a bit closer to optimum.
I'd be strongly betting on a weak capacitor ... the trick will be to
find an appropriate motor run capacitor that will fit in the Emotator
case.
73,
... Joe, W4TV
On 2/10/2024 11:47 AM, Roger Parsons via TowerTalk wrote:
Many thanks to Joe W4TV and Mike W4EF for their most helpful replies.
I managed to find about 14uF worth of non-polarised capacitors, so cobbled them
all together and connected them across the CW and CCW leads. (I should point
out that we are having unseasonably warm-ish weather at the moment so my tests
are inconclusive!) The antenna rotates, but the phase difference is now about
120 degrees instead of 90. I think that implies that the original capacitor is
still operational, but of course there are number of ways in which a capacitor
can fail. If that failure is resistive leakage then the extra capacitance might
not help. I am quite confident we will get some horribly cold weather quite
soon and I can then repeat the test.
I did already have a copy of the instructions for the units, but not the
marketing brochure which does contain some useful information. The schematics
in the instructions are all wrong, certainly when compared to my unit: My
transformer has two secondary windings - the tapped one for the motor drive and
a separate one for the control/indication. Also, the transformer is clearly
marked as 28V. I did purchase the equipment a long time ago when I was G3RBP so
it is 240V 50Hz but I can't see that would make any difference except for a
small phase change.
Anyway, thanks again for the help.
73 Roger
VE3ZI
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