1st edition, 20.04.2021
7000.05072, 1st edition, 20.04.2021
7000.05072
Installation
60
AC-mains system
Fig. 23: Interference sources in an AC-mains system
Parasitic current usually arises from the following components:
Semiconductors
Capacitive portion of the motor supply line
Parasitic elements in the motor
Operating the motors with PWM is the cause here.
The DC-DC converter in the device and the used switching power supply also produce inter-
ference that could affect the mains. The created interference of the DC-DC converter in the
device is, however, normally of little relevance due to the switched power (<5 W).
In contrast to this are the switching power supply, which supplies the controller with motor
voltage or electronics voltage, and the PWM drive. Depending on the design, quality and
effectiveness of the integrated filters (where present), the power supply can also cause
interference.
DC-mains system
Prerequisite for connecting to the DC mains is that the switching interference of the power
supply be negligible. A linear power supply can be used to reduce this interference.
Z
N
Mains impedance of mains transformer – power supply connection
ZE
1
Common-mode impedance of electronics on DC side
ZE
2
Common-mode impedance of electronics on AC side – power supply connection
ZM
1
Impedance of motor housing – controller
I
S
Parasitic current
C
P
Parasitic capacitance/filter capacitance
The qualitative assessment of a power supply can be performed with an interference
voltage test and a resistive load (e.g., fanless heater / hot plate).
DC
filter
Power adapter
AC
DC
Filter
Control
Filter
Motor
Motor
filter
DC
AC
Line
filter
PELV
Z
N
Z
E2
Z
M1
Z
E1
C
P
I
S
I
S
I
S
I
S
I
S
I
S
I
S
I
S
C
P
C
P
C
P
