FAQ No. FAQ02557
Question
What kind of noise is generated when the Servo System is used? Also what
kind of noise affects the operation of the Servo System?
Answer
1. What Is Noise?
Noise is an unexpected random signal. Some noise originates from natural
phenomena, such as lightening, but most noise that actually affects the
operation of a device is created artificially inside or external to the
device. Think of noise as an artificially created signal that travels
through a transmission path to another signal line.
2. Types of Noises
Noise Sources
Devices that cause rapid changes in voltage or current are noise sources.
The more rapid the changes, the higher the voltage, and the higher the
current, the stronger the noise source becomes.
|
Coil surge
|
An electrical
surge is generated when the voltage applied to the coil is switched
ON/OFF. |
Relay
Solenoid
Contactor |
 |
|
Capacitor
charge current |
When voltage
is applied to the capacitor it causes a large charge current flow.
|
Internal
power source
Power source
Discharge device |
 |
|
Pulse voltage
|
Pulse voltage
from PWM (See note.) |
Servo Driver
Inverter
Switching power |
 |
|
Arc discharge
|
Rapid change
in voltage when there is discharge |
Welding
machine
Discharge tube |
 |
Note: PWM (pulse width modulation)
is a method used to alter the voltage. By switching the voltage ON/OFF at
a fast switching frequency, the average voltage can be modified.
3. Transmission Path of Noise
There are the following four noise transmission paths.
(1) Electrostatic
Coupling Line
Signals that change rapidly are transmitted through a capacitor between
other signal lines that cannot be seen (an electrical field). The more
rapid the signal change, and the closer the signal line, the easier it is
to transmit the signal.
Effects
Noise transmission between signal cables
Leakage current of the motor
Malfunction of Sensors in mechanical system
(2) Conductive
Coupling Line
Signals that change rapidly are transmitted through a conductor (such as
cables and frame grounds (FG)) to signal lines and control devices.
Noise may be transmitted through the power lines, or pass through other
noise transmission paths before being transmitted by conduction.
Effects
(3) Electromagnetic
Induction Line
Signals that change rapidly create magnetic fields that change rapidly in
the surrounding. A magnetic field generates electromotive force in other
signal lines. The more rapid the signal changes, and the closer the signal
line, the larger the electromotive force.
Effects
(4) Electromagnetic Wave Line
Signals that change rapidly create magnetic waves that are emitted using
the signal lines as antennas. In a Servo System, noise may be come from
the sections shown in the diagram on the right.
Effects
Other Servomotor / Servo Driver
FAQs
 Is there a Servo System that has full-closed control?
What should the command pulse setting be to make a SMARTSTEP A-series Servo Driver operate at 3000 r/min for the various resolutions?
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