Tomms right. There's not enough iron in a 60 Hz transformer to be ran on 50 Hz,
and the number of turns is different also. From experience, I've found good
regulation to be about 12% to 13%, or in other words, a 12-13% sag in the
voltage under load. Heathkit was almost 15% but they designed their
transformers to be right on the edge, and to be as light as possible. All they
do to make an amp work on both 50 and 60 Hz is to install a 50 Hz transformer.
A 50 Hz transformer will work on 60 Hz (and run cooler), where a 60 Hz will not
run on 50 Hz. A 2500 Vdc supply under load will run about 2,212 Vdc at about
13%. That's a 288 volt drop. At 12%, 2500 Vdc would drop to 2232 Vdc with a
drop of 268 Vdc. 9-10% is almost never seen unless it's an oversized
transformer built for 100% + duty cycle (IE Military, etc. or running a 50Hz
transformer on 60 Hz). 350 Vdc sag though is way too much and is about 16% at
2500 Vdc OCV. It will work, but I don't know how hot it will run on a long ke
ydown. My guess is, pretty damn hot as the amount of iron, and wire size is
what determines a transformers temperature.
Best,
Will
*********** REPLY SEPARATOR ***********
On 3/5/06 at 2:56 PM KD7QAE wrote:
>Martin,
>
>If the XFMR is designed for 60Hz only, you will hae excessive core
>losses and high primary current as the core is being driven too close to
>saturation on each cycle. The primary current will manifest itself in
>both heating and voltage drop. The core losses will cause core
>heating. All in all a bad setup. If this is the case, you will have to
>lower the primary voltage to 5/6 of a 60Hz standard value and run on the
>matching tap the primary has (208, 230, 240) or you could buy a 50Hz
>rated transformer.
>
>Tomm
>
>Martin Sole wrote:
>
>>I had a good number of replies to my questions concerning likely output
>for
>>the Alpha 78 and in the process uncovered what is clearly a problem here
>>with the AC supply line. The distribution is done from the breaker panel
>to
>>the wall outlet with 2.5mm. Breaker panel to main breaker is 35mm and the
>>feed from the street is in what looks like the next size up from that.
>>
>>Measured about 10 volts sag in the AC line at the wall outlet with the amp
>>key down 1.5K out. Sag drops to 2.5 volts when I use 6mm cable Also
>measured
>>about 90 volts AC sag on the secondary of the transformer in the SSB
>>position. Seeing approximately 350 volts sag at the output of the power
>>supply filter. Why so much?
>>
>>Measured the ripple by looking at the voltage across the 180K HV metering
>>resistor. Saw approx 8 volts pk-pk off load rising to approx 25 volts
>pk-pk
>>at full output. Added a bank of 6x470uF capacitors and the ripple reduced
>to
>>approx 6 volts off load and neglible on load, can see the 20 metre RF
>>getting in the scope but that's all. DC still sags down 350 volts on load.
>>Changed the diodes out replacing the RCC1733 with a string of 3x1N5408's
>in
>>each case, no difference, DC still sags 350 volts.
>>
>>If this is about right can anyone explain why? Others have indicated to me
>>that they see approximately 200 volts of drop between no and full load.
>>Think I could maybe accept that but not yet cofortable with 350 volts
>drop,
>>Any ideas?
>>
>>Just as a thought , not that it would make that much difference but I
>really
>>couldn't say. Electrical supply here is 50Hz not 60Hz, would that be
>enough
>>to render the transformer a Peter Dahl 2.4KVA Hypersil meant for 60 Hz, a
>>little on the wimpy side?
>>
>>
>>73
>>Martin
>>
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>>
>>
>>
>
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