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Countermeasures Against Inverter-generated Emi - Mitsubishi Electric FR-A800 Instruction Manual

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Electro-magnetic interference (EMI) and leakage currents
• Install the earth leakage circuit breaker (ELB) on the input side of the inverter.
• In the
connection earthed-neutral system, the sensitivity current is blunt against a ground fault in the inverter output side.
Earthing (Grounding) must conform to the requirements of national and local safety regulations and electrical codes. (NEC
section 250, IEC 536 class 1 and other applicable standards)
• When the breaker is installed on the output side of the inverter, it may be unnecessarily operated by harmonics even if the
effective value is within the rating.
In this case, do not install the breaker since the eddy current and hysteresis loss will increase, leading to temperature rise.
• The following models are standard breakers: BV-C1, BC-V, NVB, NV-L, NV-G2N, NV-G3NA, NV-2F, earth leakage relay
(except NV-ZHA), and NV with AA neutral wire open-phase protection. The other models are designed for harmonic and
surge suppression: NV-C/NV-S/MN series, NV30-FA, NV50-FA, BV-C2, earth leakage alarm breaker (NF-Z), NV-ZHA, and
Countermeasures against inverter-generated
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. Though the inverter is designed to have high immunity performance, it handles
low-level signals, so it requires the following basic techniques. Also, since the inverter chops outputs at high carrier frequency,
that could generate electromagnetic noises. 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 techniques
- Do not run the power cables (I/O cables) and signal cables of the inverter in parallel with each other and do not bundle
- 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.
• Techniques to reduce electromagnetic noises that enter and cause a malfunction of the inverter (EMI countermeasures)
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 fordevices that generate many electromagnetic noises to suppress electromagnetic noises.
- Install data line filters
- Ground (Earth) the shields of the detector connection and control signal cables with cable clamp metal.
• Techniques to reduce electromagnetic noises that are radiated by the inverter to cause the peripheral devices to
malfunction (EMI countermeasures)
Inverter-generated noises are largely classified into those radiated by the cables connected to the inverter and inverter
main circuits (I/O), those electromagnetically and electrostatically induced to the signal cables of the peripheral devices
close to the main circuit power supply, and those transmitted through the power supply cables.
Inverter generated
Air propagated
induction noise
induction noise
Electrical path
propagated noise
71) to signal cables.
Noise directly
radiated from inverter
Noise radiated from
power supply cable
Noise radiated from
motor connection cable
Path (d), (e)
Path (f)
Noise propagated through
power supply cable
Noise from earthing
(grounding) cable due to
leakage current
Path (a)
Path (b)
Path (c)
Path (g)
Path (h)
power supply


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