文档介绍：Speed Control of 3-Phase Induction Motor
Induction Motor Basics
Author: Padmaraja Yedamale
NAMEPLATE PARAMETERS
A typical nameplate of an induction motor lists the
INTRODUCTION following parameters:
• Rated terminal supply voltage in Volts
Induction motors are the most widely used motors for • Rated frequency of the supply in Hz
appliances, industrial control, and automation; hence,
• Rated current in Amps
they are often called the workhorse of the motion indus-
try. They are robust, reliable, and durable. When power • Base speed in RPM
is supplied to an induction motor at the mended • Power rating in Watts or Horsepower (HP)
specifications, it runs at its rated speed. However, • Rated torque in Newton Meters or Pound-Inches
many applications need variable speed operations. For • Slip speed in RPM, or slip frequency in Hz
example, a washing machine may use different speeds
• Winding insulation type - Class A, B, F or H
for each wash cycle. Historically, mechanical gear sys-
tems were used to obtain variable speed. Recently, • Type of stator connection (for 3-phase only), star
∆
electronic power and control systems have matured to (Y) or delta ( )
allow ponents to be used for motor control in When the rated voltage and frequency are applied to
place of mechanical gears. These electronics not only the terminals of an induction motor, it draws the rated
control the motor’s speed, but can improve the motor’s current (or corresponding power) and runs at base
dynamic and steady state characteristics. In addition, speed and can deliver the rated torque.
electronics can reduce the system’s average power
consumption and noise generation of the motor. MOTOR ROTATION
Induction motor control plex due to its nonlinear When the rated AC supply is applied to the stator wind-
characteristics. While there are different methods for ings, it generates a ic flux of constant magni-
control, Variable Voltage Variable Frequency (VVVF) or tude, rotati