The current you are measuring has a phase angle relative to the mains voltage
supplied, meaning this is not real power being consumed it is apparant power,
ie not Watts but Volt-amps. You will need a phase angle meter or use a genuine
wattmeter to measure real power.
David
G3UNA
>
> From: Angel Vilaseca <avilaseca@bluewin.ch>
> Date: 2008/04/23 Wed AM 07:28:06 BST
> To: amps@contesting.com
> Subject: [Amps] current in primary of microwave oven transformer
>
> 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
>
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>
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