[Amps] Air temps leaving the amp.

[Carl]

Probably the same way Amp Supply did it with the LK-800A in the mid 80's. A 
thermal switch mounted inside the silicone rubber chimney and a wirewound 
resistor to the EBM Papst fan.

Carl
KM1H


----- Original Message ----- 
From: "Roger (K8RI)" <k8ri at rogerhalstead.com>
To: <amps at contesting.com>
Sent: Monday, February 03, 2014 6:53 PM
Subject: Re: [Amps] Air temps leaving the amp.


> On 2/3/2014 10:33 AM, Al Kozakiewicz wrote:
>> 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.
>
> How does Emtron do it?  They use a sensor in the exhaust, just above the 
> tube and there is a substantial difference between high and low speed.
> When that thing kicks into high it is not quiet.
>
> 73,
>
> Roger (K8RI)
>
>>
>> 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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>> http://lists.contesting.com/mailman/listinfo/amps
>
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