Transformer Question

HOME WORK ALERT!

You need to pay attention in class and if you do not understand something then you should ask the instructor, they can explain it easier in person.

The answer is in the question and needs only basic arithmetic to squeeze it out. Good luck with that.

Even easier than that, it needs only copying the correct number.

'....how much load i can connect to the transformer secnodary....'

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How much do you have available?

The correct answer is "only as much as the circuit protective device(s) can sustain".

400A fuses?

The transformer goes first, cables second. you'll not blow the fuse.

load it to 30va

load it to 30va MAX at 100% duty cycle at 20C`.

Can go higher/hotter for shorter duty cycle with olfactory protection on standby.

Put a 100watt bulb on the secondary (was primary) winding and plug the primary (was secondary) into a 120v source. The equivalent of the quantity of lumens produced by the bulb is the answer. Cool White bulbs are preferable. Remember that 1.8^oF = 1^oC and 1 watt-hour = 3.141394026 BTU's

Good Luck, Old Salt

". . . secd current is.13" ??

Here's something to remember for your classes: Transformers cannot create or consume Power, so the total Watts going in equals the total Watts going out.

Also good to remember is the mnemonic PEIR. This word encompasses both Watts's Law (P=E*I) and Ohm's Law (E=I*R).

(You might be using V for Voltage, the symbol E stands for 'Electromotive force' the term that was used before Volta got it named after him. Besides, PIER is easier to remember than PVIR.)

Good luck with your classes, and when you get into industry, the math gets a lot simpler, you're normally stepping voltage DOWN from the power line to the equipment level, and the stock transformers come in fixed sizes, so you just have to worry about making sure your circuit protection is selected correctly, and since the fuses and circuit breakers are also in fixed sizes, it's simple addition; add up all the loads, then pick the smallest breaker that is larger than that sum. make sure that breaker is installed 'downstream' of the transformer (between the transformer and the components) and you've got the transformer protected from overcurrent. Then to find the current load on the upstream side, you simply divide the downstream current load by the transformer step-down rating. (For example, if you are using a 2:1 step-down transformer to go from 220VAC to 110VAC, and the current drain on one 110 side is 4.8 amps, the current the transformer will need on the 220 side is 2.4 amps.) Then you simply pick the smallest current protection that is greater than the load, just like on the downstream side. You would also want to make sure the transformer is rated for the total power, measured in Volt-Amps (Volt-Amps are like Watts, but there are some differences you'll learn about in the advanced classes) The 2:1 transformer I described above would need to be rated for at least (110V*4.8A) or (220V*2.4A) = 528VA.

Good luck with your studies.

'....Here's something to remember for your classes: Transformers cannot create or consume Power, so the total Watts going in equals the total Watts going out.....'

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Hmmm. Yeah. Remember that for classes, because that is where it should stay. Warm humming transformers here in the real world continually nosh a little bit of whatever power they are working on.

Of course, ALL components consume some power, but when dealing with schoolwork, the instructor is looking for the correct math answers, and the formulae all assume 'ideal' components: All wires are zero ohms per mile, all batteries have zero internal impedance, all current sources have infinite voltage available to drive the circuit, etc.

Let the kids learn the math, THEN teach them that there real world doesn't quite line up with the math, THEN teach them how much of a 'safety factor' do build into their designs so that the final result will be 'close enough' to the math to work safely and efficiently.

Remember, you start building a pyramid by laying the foundation, you can't start with setting the capstone.

Oh good! I'm glad I trusted my instincts. I was pretty sure you had just made an initial typo when you actually meant to write: 'transformers do consumer power, meaning total watts going in is greater than total watts going out.'.

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Glad we got that all sorted out.

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I don't know very much about building pyramids at all, so I'm going to defer to you on that subject. The transformers should behave the same in a pyramid as any other structure.

Put as much load as you want. It will reflect back to the primary. You cannot drive more current through a fixed load without raising the voltage, and the voltage on the secondary is fixed.

Are you asking this on a cell phone as you are writing the exam?

Just curious....

Are you sure it is 30VA and not 30kVA?

30VA is very light for your vaguely hinted application.

30 VA is like 30W...not much at all, 1 2ft fluoro and a phone charger...

Tell us more please. What loads do you want to support?