The level of prosperity of a community is related to its capability to produce
goods and services. But producing goods and services is strongly related to the
use of energy in an intelligent way.
Motion and temperature (heat) control are paramount in energy usage.
Energy comes into use in a few forms such as thermal, mechanical and
electrical.
The level of prosperity of a community is related to its capability to produce ; p" u, f+ |. Q+ M" [/ E9 r2 agoods and services. But producing goods and services is strongly related to the 5 Q8 B, c& e C3 g1 ` b; G u# buse of energy in an intelligent way. 2 E1 m8 H1 B$ H/ ^% Z$ y. zMotion and temperature (heat) control are paramount in energy usage.) Q1 U2 r$ E& P, |3 u+ w1 u- j
Energy comes into use in a few forms such as thermal, mechanical and / B6 M8 W2 [, w* o: k" Oelectrical. " n+ X5 Q% w5 d+ L2 a' ?, PElectrical energy, measured in kWh, represents more than 30% of all used: X' V8 A9 c% t7 i
energy and it is on the rise. Part of electrical energy is used directly to produce/ [0 |: }# ~5 E% Z9 @8 H
heat or light (in electrolysis, metallurgical arch furnaces, industrial space & l% k0 d d* S9 Z' o1 [4 iheating, lighting, etc.).' i4 F5 ]8 v s7 s
The larger part of electrical energy is converted into mechanical energy in 6 ?" ~6 I/ u" y% eelectric motors. Among electric motors, induction motors are most used both for# D* c5 J7 Z4 s9 @$ ~& i
home appliances and in various industries [1-11]., I' N3 F2 X8 w
This is so because they have been traditionally fed directly from the threephase* P! \ Y6 F( G. O* m: t4 u( |
a.c. electric power grid through electromagnetic power switches with: G4 Q, u* ^( s7 O: g7 B7 w L
adequate protection. It is so convenient.2 s( r. F- q: C5 V; K
Small power induction motors, in most home appliances, are fed from the ' |( t" ^ `/ S, z3 x4 f* D6 Ilocal single phase a.c. power grids. Induction motors are rugged and have: C" i7 K8 ?( y4 C! A
moderate costs, explaining their popularity.. N( M4 Y) f( m$ [
In developed countries today there are more than 3 kW of electric motors; S8 ^0 F; h* e4 U1 d
per person, today and most of it is from induction motors.; I e4 U. k! c9 A
While most induction motors are still fed from three-phase or single-phase - ~6 O! M& P) I( Jpower grids, some are supplied through frequency changers (or power 4 \6 t; [5 A% Q# m; N& C, eelectronics converters) to provide variable speed. 7 x2 |1 v5 J. vIn developed countries, 10% of all induction motor power is converted in : o w' A- e `1 X: G4 J( Bvariable speed drives applications. The annual growth rate of variable speed6 k& p: d3 o( Z% X
drives has been 9% in the last decade while the electric motor markets showed1 [4 j$ T# U+ X
an average annual growth rate of 4% in the same time. 3 I q3 A, e0 l6 A3 a8 k) }# m; ^- nVariable speed drives with induction motors are used in transportation, - c9 ]/ R* E4 [+ a# T0 ipumps, compressors, ventilators, machine tools, robotics, hybrid or electric # q$ r9 i9 P! K% O( Y8 Cvehicles, washing machines, etc. % e% Z! Y) J j4 D, n$ y - W5 r4 j. Y" z- _) i/ a( ]斑主,给我加点分阿,叩谢!