Rockwell Automation 8520 9/Series CNC Integration Maintenance Manual Documentation Set - Manual (Page 429)

Section 7C
Power Distribution and Wiring Guidlines
7C-11
Figure 7C.13
Types of Line Noise
Power
source
Noise
source
Noise source
Power
source
A. Normal mode noise B. Common mode noise
PE PE
11234-I
9/Series
control
9/Series
control
Electrical noise varies in waveforms and magnitude over the entire
frequency width. Typical examples of abnormal phenomenon and
waveforms observed in the power source line are shown in Figure 7C.14.
Figure 7C.14
Abnormal Voltage Waveform
Slow voltage fluctuation Sharp voltage fluctuation
Flicker Higher harmonic
Voltage spike High frequency noise
One of the sources of electrical noise is a sharp current variation in
inductive circuits, as shown in the circuit of Figure 7C.15. In this circuit,
voltage V
L
applied to the inductive load L (a relay coil, for example) is
equivalent to the voltage applied to the circuit while the switch SW is
closed. If this switch is opened, the inductive load that prevents current
variation, generates a momentary high voltage called a “spike”.