Techniques And Measures For Electromagnetic Compatibility (Emc) - Mitsubishi Electric 800 Series Instruction Manual

MCCB
Power
supply
 Precautions
• Use Pr.9 Electronic thermal O/L relay.
• If the carrier frequency setting is high, decrease the Pr.72 PWM frequency selection setting.
Note that motor noise increases. Selecting Pr.240 Soft-PWM operation selection makes the sound inoffensive.
To ensure that the motor is protected against line-to-line leakage currents, it is recommended to use a temperature sensor
to directly detect motor temperature.
 Installing and selecting MCCB
Install a molded case circuit breaker (MCCB) on the power receiving side to protect the wiring at the inverter input side. Select
an MCCB according to the inverter input side power factor, which depends on the power supply voltage, output frequency and
load. Especially for a completely electromagnetic MCCB, a slightly large capacity must be selected since its operation
characteristic varies with harmonic currents. (Check it in the data of the corresponding breaker.) As an earth leakage current
breaker, use the Mitsubishi earth leakage current breaker designed for harmonics and surge suppression.
3.1.2 Techniques and measures for electromagnetic
compatibility (EMC)
Some electromagnetic noises enter the inverter to cause the inverter malfunction, and others are radiated by the inverter to
cause the peripheral devices to malfunction. (The former is called EMS problem, the latter is called EMI problem, and both is
called EMC problem.) Though the inverter is designed to be immune to noises, it requires the following basic measures and
EMS measures as it handles low-level signals. Pay attention to the electromagnetic noises that could be generated by the
inverter since the inverter chops outputs at high carrier frequency. If these electromagnetic noises cause peripheral devices to
malfunction, EMI countermeasures should be taken to suppress noises. These techniques differ slightly depending on EMI
paths.
 Basic measures
• Do not run the power cables (I/O cables) and signal cables of the inverter in parallel with each other and do not bundle
them.
• Use shielded twisted pair cables for the detector connecting and control signal cables and connect the sheathes of the
shielded cables to terminal SD.
• Ground (Earth) the inverter, motor, etc. at one point.
 EMS measures to reduce electromagnetic noises that enter the inverter
and cause it to malfunction
When devices that generate many electromagnetic noises (which use magnetic contactors, electromagnetic brakes, many
relays, for example) are installed near the inverter and the inverter may malfunction due to electromagnetic noises, the
following countermeasures must be taken:
• Provide surge suppressors for devices that generate many electromagnetic noises to suppress electromagnetic noises.
• Install data line filters to signal cables.
• Ground (Earth) the shields of the detector connection and control signal cables with cable clamp metal.
Thermal relay
MC
Inverter
Line-to-line leakage currents path
3.1 Electro-magnetic interference (EMI) and leakage currents
Motor
M
Line-to-line static
capacitances
3. Precautions for Use of the Inverter
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