Transformer or power supply question.

[DaveBN]

Sorry to seem dumb but I'm having trouble getting this thru my head. I think I know that the load on the secondary of a transformer is reflected back to the primary of the transformer. When I'm running my house on my generator for example I can hear the engine lug down when the water well or furnace start up. My question is how much power am I drawing if I leave my cell phone power supply plugged in without the phone plugged in to it? Other devices like door bells are similar. I know the cell phone charger is more than just a transformer but my question still stands. Just something I'm curious about.
Dave

 

[Steve@Advance]

The load will be miniscule.

Dry type transformers, as in door bells, HVAC, etc. draw a little.

Electronics chargers work differently, not sure what's in them, but it appears they draw zero, or very, very little when disconnected or the devise is fully charged.

A good way to tell is to feel for heat. If it is generating heat, energy is being consumed. Then compare the heat you feel to something you are familiar with, like the heat generated by an incandescent lamp.

 

[3LFarms]

I think the difference is that cell phone chargers aren t just a transformer, they are also a rectifier to change AC to DC.
Most are 110-240v input and 5 VDC output.
Lots also have electronics to monitor or filter the output. It s the electronics that constantly use energy even when nothing is connected. If they were just transformers with nothing connected to the secondary, in theory, they wouldn t use any power.

 

[Janicholson]

Electronic devices using semiconductor voltage remanufacturing,are near zero consumption. transformers are using electrons all the time. The heat from the device (measured with a hand held gun) indicate power loss as heat. Jim

 

[Russ from MN]

You should have a Kill-a-Watt, it would answer all you questions! I use mine to check to make sure my cordless drill battery is charging. The charger uses 2 watts, then when I connect the battery it jumps to 12 watts, when it's done it drops back to 2.

 

[DaveBN]

Thanks for this replies.
Dave

 

[circus]

Looking at transformer basics it looks like the supply is short circuited. Using DC the supply would be shorted. What's limiting the power, to almost nothing, going through a transformer when there's no load on the secondaries?

 

[buickanddeere]

(quoted from post at 11:14:07 01/23/23) Looking at transformer basics it looks like the supply is short circuited. Using DC the supply would be shorted. What's limiting the power, to almost nothing, going through a transformer when there's no load on the secondaries?

Inductive Reactance .

 

[circus]

(quoted from post at 08:54:34 01/23/23)

(quoted from post at 11:14:07 01/23/23) Looking at transformer basics it looks like the supply is short circuited. Using DC the supply would be shorted. What's limiting the power, to almost nothing, going through a transformer when there's no load on the secondaries?

a name doesn't help

 

[circus]

Apologies, attempts to edit prior reply results only with e20 on a blank page. :?: