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 6 c }* }, V7 X% p" E$ qgoods and services. But producing goods and services is strongly related to the8 t- U' |! P. ~( r3 _
use of energy in an intelligent way.5 t0 @" \' x/ O! i: B& {1 @
Motion and temperature (heat) control are paramount in energy usage.7 i/ w" f: Q& K2 {
Energy comes into use in a few forms such as thermal, mechanical and+ ~- h$ x" e( e* I' m! c
electrical. }( R T! N6 X! N' VElectrical energy, measured in kWh, represents more than 30% of all used 2 e) v* Y: m+ ?2 b2 j" F4 p& Denergy and it is on the rise. Part of electrical energy is used directly to produce " R* V1 i7 ?4 X: [5 F; R$ }4 I. Aheat or light (in electrolysis, metallurgical arch furnaces, industrial space 6 M$ }5 S; O; E. a" rheating, lighting, etc.)./ F d! O4 Q5 I3 \
The larger part of electrical energy is converted into mechanical energy in * |9 R2 u; s# ielectric motors. Among electric motors, induction motors are most used both for ( }" C, K& O! o: J3 Uhome appliances and in various industries [1-11]., n6 ?& a+ y, x4 r/ b( B
This is so because they have been traditionally fed directly from the threephase ) c" b4 S8 J, H2 }a.c. electric power grid through electromagnetic power switches with , d7 @# Q+ \# }4 I- z! P/ ?1 jadequate protection. It is so convenient.4 k2 |' l( m: L8 x1 g) s( w
Small power induction motors, in most home appliances, are fed from the: i/ i/ g9 a, n; i6 k
local single phase a.c. power grids. Induction motors are rugged and have 2 S6 M! \! Y8 B0 @0 vmoderate costs, explaining their popularity. 9 D) x, K% {% I- _6 n7 N( jIn developed countries today there are more than 3 kW of electric motors 2 X9 Q7 n9 F+ F oper person, today and most of it is from induction motors. N5 _ `- H# M$ Q U
While most induction motors are still fed from three-phase or single-phase5 ^8 t8 s/ b* o' R! w
power grids, some are supplied through frequency changers (or power& P! {* J0 k7 B, g' i. R4 G, R
electronics converters) to provide variable speed.3 Y4 J4 H; H/ J# q. M" U
In developed countries, 10% of all induction motor power is converted in. ^( \5 ]5 w& e5 Q( j+ d4 u. l( R
variable speed drives applications. The annual growth rate of variable speed1 ?7 I* J4 O5 X, Y7 r$ T
drives has been 9% in the last decade while the electric motor markets showed ! S7 U3 e, y1 n' l- x5 _an average annual growth rate of 4% in the same time. 2 G. _: k9 v% r3 w: e2 bVariable speed drives with induction motors are used in transportation, ( H5 B: R9 Y- `) M- j& G7 l3 {pumps, compressors, ventilators, machine tools, robotics, hybrid or electric% [/ v* v! H5 m
vehicles, washing machines, etc. 7 ?0 @0 r3 C$ x- ~! t% ~* A% P * |1 H- O, y" o7 Y斑主,给我加点分阿,叩谢!