Appendix
15.1.1 Principle of an Inverter Drive
1
5
-2
15.1 Inverter Drive Basics
This section explains the basics of an inverter drive.
15.1.1 Principle of an Inverter Drive
An inverter is a frequency conversion device that converts a commercial frequency power supply to a vari-
able frequency power supply. Fig.
15.1
show an operation diagram for a 3-phase voltage Inverter consist-
ing of switches, such as relay contacts. S
1
and S
4
, S
3
and S
6
, and S
5
and S
2
work as pairs to repeatedly turn
ON and OFF each half-cycle. Their ON/OFF timing is staggered by one-third of a cycle, so a square wave
AC voltage can be obtained as the output, as shown in Fig. 1
5.2
. The frequency of the AC output voltage
is proportional to the speed at which the switches are turned ON and OFF; in other words, inversely propor-
tional to the cycle. This is the basic operating principle of an inverter.
S
1
Ed
S
3
S
5
S
4
S
6
S
2
U
V
W
Fig 1
5
.
1
Inverter Operating Principle
S
1
, S
4
Ed
S
3
, S
6
S
2
, S
5
Switches
S
1
ON
ON
ON
ON
ON
ON
ON
ON
ON
S
4
S
1
S
6
S
6
S
3
S
5
S
5
S
2
Vu-v0
Output
voltage
Vv-w0
Vw
−
u
0
0 60
°
120
°
180
°
360
°
Fig 1
5
.2 Switch Operation and Output Voltage
In reality, a motor drive inverter requires a variable voltage and variable frequency (VVVF), so sine wave
pulse width modulation (PWM) control is used, as shown in Fig. 1
5.3
. When the carrier frequency is in-
creased, sine wave current flows through the motor.
15
Summary of Contents for CIMR-M5 Series
Page 12: ...Notes for Motor xi...
