Good mews then! My MOTs are OK.
Bad news: although no real power is delivered to my house, the power
company will bill me for it! :-)
Thanks for your help, guys!
Angel Vilaseca HB9SLV
Alex a écrit :
> ...guys this is normal behavior for all transformers!
> It is the result of the existence of a magnetizing inductance, usually
> depicted as a parallel inductance across the primary and every transformer
> has it. Don't worry about it: it's something physical and cannot be avoided!
> There are higher power transformers in which this current can reach in the
> amperes range, but it's reactive current, except for a few watts loss in the
> ohmic component: that the reason it doesn't show up as heat. These
> transformers are usually good for about 750 watts continuous, 1000 watts
> ICAS.
> Alex 4Z5KS
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Dr. David Kirkby
> Sent: Wednesday, April 23, 2008 12:08 PM
> To: Angel Vilaseca; 'AMPS'
> Subject: Re: [Amps] current in primary of microwave oven transformer
>
> Angel Vilaseca wrote:
>
>> Hi,
>>
>> I have a microwave oven transformer that I plan to use for my next HV
>> power supply.
>>
>> With the secondary unloaded and 220 V into the primary, I measured 670
>> mA through it.
>>
>> This is a 220 V unit so that means 147 Watts, with no load on the
>> secondary. Magnetic shunts were taken off.
>>
>> I have another two MOTs. Made the same measurement. They all behave the
>> same.
>>
>> On the other hand, the transformers do not hum, not smoke, not even get
>> hot, so I was wondering if this primary current could be "wattless"
>> current, that is a current that is out of phase with voltage.
>>
>>
>> Should I worry about this amount of "idle current"?
>>
>> Is this behavior particular to microwave oven transformers?
>>
>> Is there a way to know what is happening here without using a double
>> trace oscilloscope?
>>
>>
>> Vy 73
>>
>> Angel Vilaseca HB9SLV
>>
>>
>>
> The power dissipated is V*I*Cos(phi) where phi is the phase angle
> between the voltage and current. (Assuming they are pure sine waves of
> course, which is not necessary so.)
>
> There are ICs around which measure phase, but a scope is the easiest way.
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|