Vampire load solutions

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Skubie

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I have a situation where a 30 kVA transformer is serving an intermittent load. Is there a commerially available solution for automatically eliminating (minimizing) vampire load when the service side is de-energized? Thanks.
 
Skubie said:
I have a situation where a 30 kVA transformer is serving an intermittent load. Is there a commerially available solution for automatically eliminating (minimizing) vampire load when the service side is de-energized? Thanks.
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presumably by service side you really mean load side.

something is turning the load on and off. wire that into a contactor on the primary side.

not sure I want to cycle a transformer on/off all that much though.
 
petersonra said:
presumably by service side you really mean load side.

something is turning the load on and off. wire that into a contactor on the primary side.

not sure I want to cycle a transformer on/off all that much though.
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Might present a problem if the control is powered by the transformer... :D
 
:thumbup:
You can do something similar with an inverter or even a generator as the power source because you can energize the load side periodically to test for connected load. There would not be any inrush problem in such a design, although some kinds of loads would not like it.
I would not want to do that with a transformer, though!


Tapatalk...
 
Sorry, that is the way Tapatalk spells that emoticon, and I do not always remember to correct it.
(TT displays just the text when I enter it the way the forum software wants when viewing the post.)
:thumbsup:

Tapatalk...
 
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To kill a vampire,a stake thru the heart,seriously,double pole contactor on primary side,remotely controlled if necessary.A latching contactor is best,as once latched,coil requires no power input.
 
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Skubie said:
I have a situation where a 30 kVA transformer is serving an intermittent load. Is there a commerially available solution for automatically eliminating (minimizing) vampire load when the service side is de-energized? Thanks.
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BTW, I prefer the term parasitic loads. The word vampire brings to mind the old "vampire tap" on thick Ethernet cable. (You drill though the sheath, shield, and insulation to make a pressure connection to the center conductor of the cable to get access to power and signal.)
 
GoldDigger said:
BTW, I prefer the term parasitic loads. The word vampire brings to mind the old "vampire tap" on thick Ethernet cable. (You drill though the sheath, shield, and insulation to make a pressure connection to the center conductor of the cable to get access to power and signal.)
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I agree. I think the term vampire for such things is greatly overused.
I post on another forum (shock horror, I know!) and vampire loads are routinely trotted out as our nemesis.
As always, it needs perspective. I don't switch off our main television. I ought to be hung, drawn, and quartered for that totally inexcusable behaviour according to some.

My appeal to the executioner is simple and based on simple fact.
In the standby mode, the television uses 0.9W. My tiny mobile phone charger doesn't get above ambient as far as I can tell with my sensitive temperature monotiring devices AKA fingers. . Stick your finger on a 0.5W resistor running at full chat - better still, don't - unless you wish to permantly alter your fingerprint.

Common sense, though not as common as it's purported to be, ought to indicate that if something gets hot it gets hot and dissipates heat. If it doesn't, it doesn't.
 
True, but keep in mind that the area through which the heat is shed has a big effect on the temperature that you feel.

If the charger has 100 times the surface area, then it will have 1/100th of the temperature rise.

Tapatalk...
 
GoldDigger said:
True, but keep in mind that the area through which the heat is shed has a big effect on the temperature that you feel.

If the charger has 100 times the surface area, then it will have 1/100th of the temperature rise.

Tapatalk...
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Yes. Of course, size matters. That's why I mentioned that the charger was tiny, you see.

It possibly won't surprise you that, with me being in the field I'm in, I routinely have to do calculations for thermal dissipation from electrical enclosures.
I've developed programmes for surface heat and force air cooling.
For something the size of the charger, a small fraction of a watt would produce an appreciable temperature difference. I can detect none.
 
Besoeker said:
Yes. Of course, size matters. That's why I mentioned that the charger was tiny, you see.

It possibly won't surprise you that, with me being in the field I'm in, I routinely have to do calculations for thermal dissipation from electrical enclosures.
I've developed programmes for surface heat and force air cooling.
For something the size of the charger, a small fraction of a watt would produce an appreciable temperature difference. I can detect none.
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Many current design chargers do not use transformers, so there may be essentially no parasitic VA, let alone parasitic watts. One of my wall chargers does have a power on LED in it that makes a credible night light though. :)

I tend not to worry about those nearly as much as constantly on appliances.
My Droid phone keeps reminding me to unplug the charger from the wall every time I unplug it from the phone, though.
 
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