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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