How can we convert 1,000Vdc to a constant 30Vdc using a buck converter? What will be the required components specifications?
Unfortunately, it is practically impossible to convert a 1000V dc to 30V dc using a buck converter.In theory it is possible to get any voltage which is less than the input voltage, from the buck converter. However, a buck converter duty cycle should never be decreased less than 0.2 or 20% in practice. For your case it becomes 0.03 or 3% duty cycle.Observe the image “Buck Efficiency” below. You should see a steep decrease in efficiency when the buck converter is operated below 0.2 duty cycle. This increases the loss in the system. Heat increases rapidly which in turn reduces the efficiency some more. Thermal steady state becomes very hard to achieve and you have to overrate the system to a point where your design becomes impractical.The reasons behind this phenomenon are the parasitic resistance of the inductor and capacitor, the losses in the power semiconductor, the magnetic loss etc.So how to achieve 1000V to 30V dc conversion?You can use some transformer based topologies like full bridge, flyback or forward converter.If your power rating is less than 100W, use a flyback converter. If your power rating is in between 100W to 400W, use a forward converter. If you want to go for even higher power, use a full bridge converter.A typical full bridge converter looks like this.It is possible to go for 1000:30 ratio because of the transformer. You can have a big ratio at the transformer and you can design your system to operate at 50% duty cycle. This method is far more efficient than having a normal buck converter.Image source:Thanks for reading.Arpan
What is wrong with the Indian education system?
9th standard:PTA meetingPhysics Teacher: Your son is very smart. He is hardworking too. Dad: Thanks sir! He studies well. He is passionate about physics.Physics Teacher: Yes. He has what it takes to be an IAS Officer. Prepare him for Civil Services. He would be a great officer.Dad: That's good to hear sir. I am just a 9th standard guy. All I knew was that I loved applying physics to daily life activities. I knew I loved Maths too. But I did not know about my future. I did not know what I would be or what I wanted to be. I approached my teacher the next day.Class - the next day:Me: Sir. I like physics. What is its future.Physics Teacher: The future of physics is full of possibilities. There is infinite scope for exploring the field.Me: Then why did you want me to be an IAS Officer.Physics Teacher: Its a very stable job. You get security. You can get others to do your work for you. You will have many servants. You can earn very much. Even though the salary from government is less, you get lots of gifts (not so subtle). If you pursue physics, you can't earn much. Home:Mom: How did the meeting go. Dad: Great! His teacher told me that he has what it takes to even crack Civil Services.Mom: He's too young. Let us give him a few years before we push him towards his goals. (My mother is a professor. I am lucky. Not all are lucky to be afforded this freedom.)Conclusion:I tell my teacher I like his subject. He tells me it has good future. But money is the ultimate objective and it has less scope to earn money. He tells me to pursue another field. I feel there is something fundamentally wrong if we educate our younger generation that one field has more priority over another. All are equal. It just depends on one's passion towards a field and a drive to pursue it.As someone said: "Where would they be if Lata Mangeshkar picked up a cricket bat and Sachin Tendulkar became a singer."
Why is a short-circuit test, in the case of transformers, done with the high-voltage side only?
The reason that a power transformer short circuit test is performed on the HV side is mostly due to the limitations of the power supply used to perform the test. Let us review:The purpose for performing a short circuit test in the first place is to measure the positive-sequence impedance of the transformer [math]Z[/math]. It is expressed as a percentage of the rated voltage applied to the transformer that results in rated current when the output is short circuited. It is measured at the factory using a balanced short circuit test as shown in the following single-phase equivalent circuit:The low-voltage (LV) winding is shorted. A balanced three-phase, alternating current (AC), variable voltage source is used to excite the high-voltage (HV) winding. The voltage source is increased from zero until rated current is measured in the HV winding using an ammeter (A). Once this operating point is reached, the HV voltage is measured with a voltmeter (V). The impedance-voltage is then expressed as a percent of the rated voltage of the transformer [math]Z=V/Vrated×100[/math]. Since the full-load current of the HV winding is typically only in the 100’s of amps range, the power supply capability can be reduced (e.g., a less expensive power supply).If the test was performed on the LV winding, the power supply would need to have the capability of producing 1000’s of amps since the full load current of the LV winding is greater by the voltage ratio [math]HV/LV[/math] of the transformer.Thus, all short circuit tests are performed on the HV side because the power supply capabilities (and cost) are reduced.Read more about this in my answer to How do I connect a transformer for short circuit test?