Alternating Current Flashcards
I & V phases for inductor,resistor & capacitor
Inductor - I lags V
Resistor - same
Capacitor - I leads V
Why capacitor blocks DC allows AC?
X(c) prop 1/nyu
For DC, nyu = 0 & for AC, nyu = 50Hz
So in DC X(c) = 1/0
So it has infinite resistance
Average power for inductor,capacitor & resistor
Inductor & capacitor - 0, resistor - <p> =i(m)²R/2 = i(rms)²R
Series LCR circuit
V = iR + Ldi/dt + q/c
V = V(R) + V(L) + V(C)
V(RM) = imR
V(cm) = imX(c)
V(m) = im[R²+(X(c) - X(L)²]½
i(m) = V(m)/Z
Z = [R² + (X(c) - X(L)²]½
tanO
Xc-Xl/R
nyu=
1/2pi(LC)^1/2
Sharpness of resonance
Wo/2ΔW
Quality factor
1/R (L/C)^1/2
Transformer?
Device used to change AV from greater value to smaller value or vis versa. It works on principle of mutual inductance
power ratio with current and turns
Vs/Vp = Ns/Np = Ip/Is
Energy loss in transformers
Copper, Hysteresis, eddy current and flux leakage loss
Hysteresis loss:
Hysteresis loss: The AC carries the iron core through cycles of magnetisation & demagnetisation. Due to this, energy is lost in the form of heat. It can be minimized by using core material having narrow hysteresis loop.
Eddy current loss:
Eddy current loss: The alternating Magnetic flux induces eddy currents in the iron core which leads to some energy loss in form of heat. This can be minimized by using laminated iron core.
Copper loss:
Copper loss: Some energy is lost due to heating of copper wires used in primary & sec windings. It can be minimized by using thick copper wires of low resistance.
Flux leakage
The magnetic flux produced by the primary may not fully passthrough the secondary. Some of the flux may leak into air. This can be minimized by winding the primary & secondary coils over 1 another.
