Recent content by david90

How can phase shift of L1 be both IB+IR and IB-IR?

Hi, Regarding the picture below, the author calculates L1's current with KCL equation IR-IB = L1. Why is the KCL equation not IR+IB = L1 if the voltage of phase B and Phase R at one point during their cycle can be both positive (Assume positive voltage means current go toward the node)? If...

I think I understand now. The UPS can't supply 1000W but it can supply 1000VA because 866VAR quickly returns to the UPS. I can see how the size of the battery creates this limitation. Thanks

With regards to the internals of the UPS, what are differences between a UPS with 1000VA / 500W rating and a UPS with 1000VA / 1000W rating? Restating the question in another form, why does the 1000VA / 500W UPS require 500VAR to go back to it while the 1000VA / 1000W UPS does not? I'm still...

Assume the output rating is 1000VA / 500W. From the perspective of the UPS, what would happen if I connect a 1000W purely resistive load to the output? Which parts of the UPS would overheat? What I'm confused about is If the UPS can output 1000VA then why does it care that resistor is...

Why do some UPSs have both Volt-amp and watt rating? According to APC, the connected load shouldn't exceed the UPS's VA and watt rating. Why? If I had a UPS with 1000VA and 500W rating, why can't it power a load consuming 1000VA @ 900W? If a UPS can output 1000VA, why does it care how much...

What if we assume the motor in both cases are operating at their maximum rpm and the force at the bicycle's wheel is constant?

yes

Given f=ma, f/m=a v=a(t), v=(f/m)(t) Is it wrong to apply "v=(f/m)(t)" to situation where the force is generated by a motor? If no, then how come "v=(f/m)(t)" doesn't consider the motor's RPM? From my understanding, velocity should also be determined by the motor's rpm. For example, an...

I read a wiki article on electrical noise and it said that two wires running in parallel can cause noise due to capacitive coupling. "Capacitive coupling - A current through two resistors, or any other type of conductor, close to each other in a circuit can create unwanted capacitive coupling...

That would be nice. Thank you!

I work with industrial electrical system and I got a question regarding electrical noise caused by electromagnetic radiation. In an industrial environment, cables carrying an analog signal are shielded and its drain wire is Earth grounded at one end of the cable. When electromagnetic radiation...

I see. If a ground fault occurs at the transformer, then no the CB will not trip. However, the ground fault will trip the CB or fuse ( Not shown in your picture) that protects the primary winding of the transformer.

Engineers are thinkers. Buying a car that you can't afford is not thinking. hehe. However, it's good to spoil yourself on a nice car if you can afford it. Engineers have money so it shouldn't be a problem.

I'm not sure what you mean. Under normal condition, current flows through the load (represented by the resistor symbol). Under a ground fault condition, current flows through the ground wire. In the picture below, I drew the path of the ground fault current. Very very little current will flow...