[Amps] Air temps leaving the amp.

[Al Kozakiewicz]

Yes, that is the defining characteristic of an induction motor! 

The only way to vary the speed of such a motor is either by changing the frequency of the power source or with a variable speed transmission.

Al
AB2ZY

________________________________________
From: Amps [amps-bounces at contesting.com] On Behalf Of Jim Garland [4cx250b at miamioh.edu]
Sent: Monday, February 03, 2014 10:24 AM
To: 'Roger (K8RI)'; amps at contesting.com
Subject: Re: [Amps] Air temps leaving the amp.

This raises an interesting issue. How does one reduce the impeller speed on
a blower with a 120 VAC motor (capacitor start)? I've done some tests on
several blowers (3370 rpm) and find the rpm doesn't vary appreciably as the
voltage is varied over a significant range. Once the voltage gets low
enough, of course, the blower stalls, but the rpm doesn't vary with the
voltage. I suspect this is an inherent property of induction motors. I first
discovered this effect years ago when I tried to reduce the blower speed of
a Rotron blower in an 8877 amp. I switched in a 24V transformer to lower the
voltage from 120V to 96V, but discovered it didn't make much difference.
73,
Jim W8ZR

>Find what
> blower speed gives the required pressure. Then back off to where the
> noise is comfortable. Use a sensor in the output air so when the temp
> rises it can kick into high blower.  Use a couple sensors to give more
> leeway. Normal, high, and afterburner.  IOW.  If a little more speed
> will keep the temp in range on SSB, there is little reason to run more
> pressure than required, but when heavy duty work like digital or slow
> scan heats things up, then go for max cooling,


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