Power Electronics Terminology:
Power Electronics Terminology: Terms used in Power electronics study...
Steady state; Steady state is that condition in which the characteristics remain within the limits for normal operation steady state characteristics throughout an arbitrarily long period of time. Steady state conditions may include lesser transients.
It is a multiple of the fundamental frequency. It can be even or odd multiplies of the sinusoidal fundamental frequency.
Ex. the fundamental frequency of the AC electric power distribution system is 50Hz. The 2nd harmonic is 100Hz, 3rd harmonic is 150Hz, 4th harmonic is 200Hz, etc.
The multiple, that the harmonic frequency is of the fundamental frequency, is called the harmonic order.
Linear Electrical Load:
A linear electrical load is one, which draws a purely sinusoidal current when connected to a sinusoidal voltage source.
e.g. Resistors, Capacitors, Inductors.
Many of the traditional devices connected to the power distribution system, such as transformers, electric motors and resistive heaters, have linear characteristics.
Non-Linear Electrical Load:
A non-linear electrical load is one, which draws a non-sinusoidal current when connected to a sinusoidal voltage source. e.g. Diode bridge, Thyristor bridge, etc.
Many power electronic devices, such as variable speed drives, rectifiers and UPSs, have non-linear characteristics and result in non-sinusoidal current waveforms or distorted waveform. Example of distorted waveform is given here
Transients; A transient is a changing value of a characteristic that usually occurs as a result of normal disturbances such as electric load change and engine speed change. A transient may also occur as a result of a momentary power interruption or an abnormal disturbance such as fault clearing.
a. Transients that do not exceed the steady state limits are defined as lesser transients.
b. Transients that exceed the steady state limits but remain within the specified normal transients limits are defined as normal transients.
c. Transients that exceed normal transient’s limits as a result of an abnormal disturbance and eventually return to steady state limits are defined as abnormal transients.
Power Supply Terms:
The following list of definitions are terms that are primarily used to describe power supply designs:
Transient: A momentary power interruption or an abnormal disturbance.
Transients that exceed the steady state limits but remain within the specified normal transient limits are called as normal transients.If the transients exceed the normal transient's limits due to abnormal disturbance are called as abnormal transients.
Utilization Equipment: The equipment which receives the power from electric power system.
Auxiliary Outputs: Outputs of a multiple output power supply that are not considered as the main output(s).
Bandwidth: The frequency band over which output ripple and noise components are specified.
Choke: An inductor designed to specifically carry a large DC current component.
Converter: Any switch mode PS which converts a DC input voltage to a different DC output voltage.
Cross Regulation: Regulating effects on one output as a result of changes on another output.
Current Foldback: A method of overload protection in which the output current is reduced in the overload region as the load resistance decreases. This method of protection can cause Lockout.
Derating: The reduction in one operating parameter as a result of the change in some other parameter, for example, reduction in output power based upon increase of PWB temperature.
Efficiency: The ratio of Delivered Power to Input Power as a percentage.
Flyback: The property of an inductor that enables it to reverse its terminal voltage when conducted current is interrupted.
Galvanic Isolation: Indicates no direct DC path between two circuits.
Inrush Current: The peak value of the input current when the supply is first switched on.
Isolated Converter: A DC/DC converter that provides true galvanic isolation between input and output power.
Line Regulation: The change in the output voltage regulation as a result of the input line voltage change.
Load Regulation: The change in the output voltage regulation as a result of a change in the output load.
Lockout: A condition in which the power supply fails to establish its correct working condition on initial start-up or after a transient load condition.
Main Output: The principle, or highest power, output of a multiple-output PS. The control loop is normally closed on the Main output.
Overshoot: A transient excursion of the output beyond the normal regulation limits as result of turn-on, turn-off, or load step changes.
Recovery Time: Time necessary for the output to recover to a value within regulation limits after a step change in the load.
Remote Sensing: A provision for measuring and regulating the output voltage at the load instead to the PS output terminals.
Soft Start: A method of controlling the initial rate of increase in duty ratio in a PS during the turn on transient. Normally used to reduce stress on the internal components and to prevent transformer saturation.
Thermal Protection: A method of preventing failure of the PS as a result of an over temperature condition.
Undershoot: A transient excursion of the output beneath the normal regulation limits as result of input or output step changes.