The trick that I use is a "motor run" capacitor in series - typical
values are 1-15uF 440VAC rated. You can use a single cap or
more than one if you want more than two speeds and switch
across them.
On one of my big amps I have an Airflow 45CTL with a 6u8
in series on receive, when on TX its shorted out by a relay operated
from the PTT line. The relay is controlled from a simple timing circuit
(FET/diode/capacitor/resistor) so that it remains on full power blow
for about 10s after PTT is released to remove most of the excess
heat from the 4CX1000A after which it drops back to a more
acceptable level for the shack (or tent, when contesting).
Mike G8TIC/M0VHF
> How about a diode switched in series with the AC line for the "quiet
time"?
> I have used that in the past, did not slow down the blower as much as you
> would suspect, but did the job! 73 - Mark, AA6DX
> ----- Original Message -----
> From: "Neil Carr G0JHC" <g0jhc@blueyonder.co.uk>
> To: <amps@contesting.com>
> Sent: Monday, November 17, 2003 10:47 PM
> Subject: [Amps] slow down circuits for 240v blower
>
>
> I'm wanting to fit a front panel control on my latest amp project which
> will allow me to reduce the speed (and noise) of my EBM blower, (G2E-140)
> especially during long periods in receive.
>
>
>
> This doesn't have to be anything clever that monitors temp or slows
> down/speeds-up when keying/unkeying the amp (but I would consider
something
> if simple to construct), But nothing more than an inductive control. I
have
> of course already made the mistake of trying a number of off the shelf
house
> hold items (that were resistive, silly me), and also have a 240v ceiling
fan
> control board, which for some reason, although works fine, produces a
heavy
> hum on the motor? My simple varibale Variac does a great job.
>
>
>
> Whats out there please!? or how do i get rid of the hum on ( a number of
> fan speed controls I've tried)
>
>
>
> Any guidance appreciated.
>
>
>
> 73 Neil G0JHC
>
>
>
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