16-11-2012, 04:13 PM
Power Electronics
[attachment=39814]
The power electronic system
INTRODUCTION
A power electronic system will consist of a power source, filtering, a power
converter, a load and a control circuit. The block diagram is shown in
The power source could be three-phase, or single-phase, a.c. mains or it could
be a portable supply such as a d.c. battery.
A filter may be necessary to prevent any harmonics generated by the converter
from being fed back to the mains or from being radiated into space.
National and international standards for electromagnetic compatability
(EMC) are now legally binding on manufacturers of power electronic equipment,
The control circuit monitors the condition at the load, compares this with
preset values and then adjusts the converter drive as necessary.
The power conditioner is an arrangement of semiconductor devices all operating
in the switching mode. This means that the device is switched from cut-off
to saturation ('off' to 'on') by the application of gate, or base, drive pulses. The
ideal switch would have full voltage across it when 'off', and zero voltage
across it when 'on'.
POWER SWITCHES
Commonly available power switches are given in Table 1.1; this is not exhaustive
and others are obtainable. Much research and development is going on and
new devices will appear; also the power handling capability of existing devices
is improving year by year. The forward voltage drop figures should be taken as
a guide only, as this will depend on the gate or base drive values and on the
rating.
ANALYSIS OF POWER CONVERTER OPERATION
The level of mathematics required to solve some of the converters' Kirhhoff's
law time-varying equations may not yet have been fully covered by students at
the start of their second year. However, this need not prevent the understanding
of the operation of the power electronic circuit, nor prevent solution of problems
on the circuit's behaviour. Most of the solutions of the equations are
worked through in the book and the important equation on which performance
depends is enclosed in a box, e.g.
APPLICATIONS OF POWER ELECTRONICS
It is astonishing to realise that there is hardly a home, office block, factory, car,
sports hall, hospital or theatre without an application, and sometimes many
applications, of power electronic equipment.
Some typical applications are given below:
9 industrial processes in the chemical, paper and steel industries;
9 domestic and theatre lighting;
9 motor drives from food mixers and washing machines through to lifts and
locomotives such as 'Eurostar';
9 power supplies for laboratories and uninterruptible power for vital loads;
9 generation and transmission control;
9 heating and ventilating of homes and office blocks.
[attachment=39814]
The power electronic system
INTRODUCTION
A power electronic system will consist of a power source, filtering, a power
converter, a load and a control circuit. The block diagram is shown in
The power source could be three-phase, or single-phase, a.c. mains or it could
be a portable supply such as a d.c. battery.
A filter may be necessary to prevent any harmonics generated by the converter
from being fed back to the mains or from being radiated into space.
National and international standards for electromagnetic compatability
(EMC) are now legally binding on manufacturers of power electronic equipment,
The control circuit monitors the condition at the load, compares this with
preset values and then adjusts the converter drive as necessary.
The power conditioner is an arrangement of semiconductor devices all operating
in the switching mode. This means that the device is switched from cut-off
to saturation ('off' to 'on') by the application of gate, or base, drive pulses. The
ideal switch would have full voltage across it when 'off', and zero voltage
across it when 'on'.
POWER SWITCHES
Commonly available power switches are given in Table 1.1; this is not exhaustive
and others are obtainable. Much research and development is going on and
new devices will appear; also the power handling capability of existing devices
is improving year by year. The forward voltage drop figures should be taken as
a guide only, as this will depend on the gate or base drive values and on the
rating.
ANALYSIS OF POWER CONVERTER OPERATION
The level of mathematics required to solve some of the converters' Kirhhoff's
law time-varying equations may not yet have been fully covered by students at
the start of their second year. However, this need not prevent the understanding
of the operation of the power electronic circuit, nor prevent solution of problems
on the circuit's behaviour. Most of the solutions of the equations are
worked through in the book and the important equation on which performance
depends is enclosed in a box, e.g.
APPLICATIONS OF POWER ELECTRONICS
It is astonishing to realise that there is hardly a home, office block, factory, car,
sports hall, hospital or theatre without an application, and sometimes many
applications, of power electronic equipment.
Some typical applications are given below:
9 industrial processes in the chemical, paper and steel industries;
9 domestic and theatre lighting;
9 motor drives from food mixers and washing machines through to lifts and
locomotives such as 'Eurostar';
9 power supplies for laboratories and uninterruptible power for vital loads;
9 generation and transmission control;
9 heating and ventilating of homes and office blocks.