Power Consumption

[Badar]

Hi.
I am powering a tansformer.If i don't connect any load to the secondary will the power be consumed?

 

[ericgibbs]

hi,
If no secondary load then.

The transformer primary will warm up a little due to the resistance of the winding.
There are also very small losses due to the magnetic fields which cause the transformer core to warm up.

Eric

 

[RODALCO]

Magnetising current

Magnetising current
Power will be consumed by the TX as magnetising current. because of the change of flux because of the 50 or 60 Hz frequency.

Depending upon the size of the TX it will vary.

For a small 30 VA TX, this magnetising current is around 80 mA's for a 230V 50 Hz TX.

Copperlosses, are only of significance if the TX is loaded, these do increase with load.

Ironlosses, are losses within the laminated iron pack and normally steady and added as part of magnetising losses.

 

[Hero999]

In general the losses are smaller for larger transformers than for smaller trnasformers. You would probaby save on your electricity bill if you could remove all the small transformers from all the DC ELV (Extra Low Voltage) aplliances in your house and ran them all from a DC bus generated by a single transformer.

What with all theis "CO2 emission reduction" BS I can imagine a standard being set for a separate ELV for the domestic consumer.

 

[gromikov]

The bigger the transformer the "bigger" the losses.
Ther are nor real big losses without a charge in the secondary coil
Due to the warmup caused by the transformer coil

 

[ericgibbs]

hi,

The bigger the transformer the "bigger" the losses.

Would you care to quantify this 'bigger' loss?

 

[gromikov]

hi,

The bigger the transformer the "bigger" the losses.

Would you care to quantify this 'bigger' loss?

Some devices use a small amount of electricity even when they're not on. For example, VCR's and microwaves draw a small amount to power the time display. This amount is often 5 watts or less. Devices which run off transformers also draw a small amount of power.

 

[ericgibbs]

hi,

A well designed 'large' mains transformer can be far more efficient and have lower energy losses than many lower cost smaller transformers.

Its incorrect to say The bigger the transformer the "bigger" the losses.

Your last post dosn't explain, The bigger the transformer the "bigger" the losses.

Some devices use a small amount of electricity even when they're not on. For example, VCR's and microwaves draw a small amount to power the time display. This amount is often 5 watts or less. Devices which run off transformers also draw a small amount of power

Eric

 

[Hero999]

That's true, a 1VA transformer will be 50% efficient while a 1MVA transformer will be 99.999% efficient.