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Installing and selecting MCCB
Install a molded case circuit breaker (MCCB) on the power receiving side to protect the wiring at the input side of the inverter
or the converter unit. 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 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 or the converter unit to cause the inverter/converter malfunction, and others
are radiated by the converter 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 or the converter unit is designed to have high
immunity performance, it handles low-level signals, so it requires the following basic techniques. Pay attention to the
electromagnetic noises that could be generated by the inverter since the inverter chops outputs at high carrier frequency. For
prevention of malfunction of peripheral devices caused by electromagnetic noises EMI precautions 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 or the converter unit 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 or the converter unit, motor, etc. at one point.
EMS measures to reduce electromagnetic noises that enter the inverter
or the converter unit 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 or the converter and it may malfunction due to electromagnetic noises, the
following measures must be taken:
• Provide surge suppressors for devices that generate many electromagnetic noises to suppress electromagnetic noises.
• Install data line filters to signal cables (refer to
• Ground (Earth) the shields of the detector connection and control signal cables with cable clamp metal.
page
54).
3. PRECAUTIONS FOR USE OF THE CONVERTER UNIT
3.1 Electro-magnetic interference (EMI) and leakage currents
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