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I really need some help please...


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I have a really stupid lecturer who can't teach and an assignment due in 6 days. Any help someone could give me, a push in the right direction, not necessarily the answers would really help :)


For low voltage lighting in the reatil section of a winery (6 halogen lights rated at 20W) a 12V supply is to be derived from the mains.


1. Calculate the transformer turns ratio

2. Calculate the load current and supply current

3. what are the pros and cons of using a 12V battery for this application


THANKYOU so much I really need any help I can get

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Hello 12892134


Welcome to the forum.

While we like to be helpful, we may choose not to do your homework for you!!


A transformer steps voltage down and current up, or it steps voltage up and current down. basically VxI (VA) input equals VxI (VA) output.

The voltage reduces with the turns ratio and the current increases.

i.e. half the turns on the secondary and the voltage will halve and the current will double.


For the abttery situation, abtteries need to be charged, and more important, if you have long cables at high current, you have higher voltage drop than if you have high voltage and low current.

1 volt drop at 110 volts or 230 volts is small, 1 volt drop at 12 volts is significant.


Best regards,

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thank you... does anyone have any ideas on the load current and supply current. My delimma is that I have only been given the power for the lights and the supply voltage but for the life of me i can't figure out what equation to use which gives me the current or is the question saying that 12 v is needed to run the 6 lights at 20W each so then it would be


power=voltage x current (which would give me the load current)


then what is the supply current??


any help is really appreciated!!



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Hello 12892134


Refer back to my earlier posting.

For a transformer, VA in = VA out.


For a resistive load, if we ignore transformer losses, then VA = power, so power in = power out.


Best regards,

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