Sunday, July 14, 2013

Biasing, Forward-biased, Reversed-biased, Zero-biased in diode, p-n junction


- applying voltage to a circuit to allow or prevent current flow.

Zero bias

- equilibrium condition in a diode or pn junction
- no external voltage applied in a p-n junction
- potential difference (built-in potential) exists across the junction

Reverse bias

- cathode voltage higher than anode voltage
- barrier voltage increases
- depletion zone width increases
- depletion region widens
- junction barrier widens
- resistance becomes greater
- prevents flow of charge carriers
- no current will flow (or minimal current flows)
- acts like an insulator

Forward bias

- barrier voltage decreases
- depletion width is reduced
- barrier potential lowered
- electrical resistance reduced
- allows current flow (conduction mode)
- current flows in the same direction on both sides of diode
- behaves like a conductor

P–N Junction Diode

- electric charges flow in one direction only
- like a mechanical check valve in piping (allowing fluid to flow in one direction only)

Friday, March 15, 2013

Droop Frequency, Droop Speed, Voltage Droop

Droop definition
The meaning of Droop is to weaken, fade, sag or lose energy.

What is frequency droop? What is speed droop?
Frequency droop or Speed Droop is the loss or decrease in frequency or speed as it go from no load to full load.

Percent Droop Frequency
Percent Droop Frequency is the ratio of the difference in no load and full load frequency to the full load frequency.

% Droop Frequency = [ (No Load Frequency - Full Load Frequency) / Full Load Frequency ] x 100%
Generator No Load Frequency = 63 Hz
Generator Full Load Frequency = 60 Hz

% Droop Frequency = [ (63 Hz - 60 Hz) / 60 Hz ] x 100%
% Droop Frequency = (3/60) x 100%
% Droop Frequency = 5% droop

Percent Droop Speed
Percent Droop Speed is the ratio of the difference in no load and full load speed to the full load speed.

% Droop Speed = [ (No Load Speed - Full Load Speed) / Full Load Speed ] x 100%
Motor No Load Speed = 1872 rpm
Motor Full Load Speed = 1800 rpm

% Droop Speed = [ (1872 rpm - 1800 rpm) / 1800 rpm ] x 100%
% Droop Speed = (72/1800) x 100%
% Droop Speed = 4% droop

What is droop voltage?
Voltage droop is the decrease or loss  in output voltage as it drives a load.