Siemens A1 User Manual
International English
Introduction
MICROMASTER Applications Handbook
3
Torque
Flux, Voltage
Speed ( X 50/60)
Torque
Capability
0
0.5
1.0
1.2
1.5
Figure 1-3
Torque Reduction above Base Speed
Therefore in order to control the speed of a standard AC motor, the applied
frequency and voltage must be controlled.
frequency and voltage must be controlled.
Although it is difficult to control voltage and frequencies at these high powers, the
use of a standard induction motor allows a cost-effective speed control system to
be built.
use of a standard induction motor allows a cost-effective speed control system to
be built.
1.2
The Variable Frequency Inverter
An electronic converter that converts Direct Current (DC) to Alternating Current
(AC) is known as an inverter. Electronic speed controllers for AC motors usually
convert the AC supply to DC using a rectifier, and then convert it back to a variable
frequency, variable voltage AC supply using an inverter bridge. The connection
between the rectifier and inverter is called the DC link. The block diagram of a
speed controller (often called an inverter) is shown in Figure 1-4.
(AC) is known as an inverter. Electronic speed controllers for AC motors usually
convert the AC supply to DC using a rectifier, and then convert it back to a variable
frequency, variable voltage AC supply using an inverter bridge. The connection
between the rectifier and inverter is called the DC link. The block diagram of a
speed controller (often called an inverter) is shown in Figure 1-4.
Motor
Supply
Rectifier
DC Link
Inverter
+
-
Figure 1-4
Inverter Block Diagram