# Search results

1. ### Transformers - winding resistance and leakage reactance

transformers -- winding resistance and leakage reactance Does anyone know what is meant by: 'determine the combined winding resistance and leakage reactance referred to the primary side'?
2. ### Largest achieveable phase margin

My question is: With a controller gain that meets the condition on the ramp set point, what is the largest achievable phase margin? I have no idea what the solution is saying! Does anyone know what this means exactly??

Also can anyone explain why delta connection produces 1/3 of the instantaneous power given the same Z and V?

A balanced 3 phase load is rated at S=10KVA and 500V. The device is operating at 90% nominal voltage and 100 % line current. The question is: if the load is delta connected, find the phase current in per unit and SI units. I calculated correctly that the per unit line current value is...
5. ### Conversion to phasor from cos and sine

Solved it :D Please let me know if anyone would like me to go over it.
6. ### Conversion to phasor from cos and sine

I am given the problem: 100Sin(ωt+30) +20cos(ωt) and the solution is 78.7<38.9degrees How do I convert to phasor form? I know for this calculation I need the following relationship: √2Esin(ωt-∅)=Ee^(-j∅) At first I tried making both sines and then splitting up 100Sin(ωt+30) and...
7. ### Closed loop damping ratio

From control systems: I am asked to find the value of K that gives the closed loop damping ratio of 1/sqrt2. The value for the complimentary sensitivity is T(S)=(2KS +4K)/(s^3 +162S^2 +(320+2K)S +4K) so how do I find the value for K? I tried putting it in the general equation, but it...
8. ### Laplace transform heaviside function

I have a question asking for the inverse laplace transform of (e^(-s))/(s^2+pi^2). I split it up to (e^(-s))/s x s/(s^2+pi^2) and got u(t-1)cos(pi(t-1)),but the correct answer is (sin(pi(t-1)/pi)u(t-1). So here it was split up to (e^(-s))/pi x pi/(s^2+pi^2) and I don't understand where the...
9. ### Null vector

I have a question in my notes saying 'Find a null vector for the following matricies'. They are all 2x2. Can you give an example showing how to do it?
10. ### Null vector

I have no idea what this is! Please can someone explain comparing to a 3x3 matrix?