Techniques to reduce electromagnetic noises that are radiated by the inverter to cause the peripheral devices to malfunction (EMI countermeasures) 1 Inverter-generated noises are largely classified into those radiated by the cables connected to the inverter and inverter main 2 main circuit power supply, and those transmitted through the power supply cables.
circuits (I/O), those electromagnetically and electrostatically induced to the signal cables of the peripheral devices close to the 3 Inverter generated electromagnetic noise Air propagated noise …Path (a) Noise directly radiated from inverter Noise radiated from power supply cable …Path (b) (e) 5 Noise radiated from motor connection cable …Path (c) Telephone Electromagnetic induction noise …Path (d), (e) (g) (b) (g) 5 Electrostatic induction noise (a) Sensor power supply …Path (f) (a) Noise propagated through power supply cable Instrument Receiver (c) Inverter (d) (f) (h) 6 Electrical path propagated noise …Path (g) Noise from earthing (grounding) cable due to leakage current …Path (h) Motor M (c) Sensor 7 8 9 10 51 3.
PRECAUTIONS FOR USE OF THE INVERTER 3.1 Electro-magnetic interference (EMI) and leakage currents Noise propagation path Countermeasure (a), (b), (c) When devices that handle low-level signals and are liable to malfunction due to electromagnetic noises, e.g. instruments, receivers and sensors, are contained in the enclosure that contains the inverter or when their signal cables are run near the inverter, the devices may malfunction due to by air-propagated electromagnetic noises. The following countermeasures must be taken: • Install easily affected devices as far away as possible from the inverter.
• Run easily affected signal cables as far away as possible from the inverter and its I/O cables. • Do not run the signal cables and power cables (inverter I/O cables) in parallel with each other and do not bundle them. • Inserting a line noise filter into the output suppresses the radiated noise from the cables. • Use shielded cables as signal cables and power cables and run them in individual metal conduits to produce further effects. (d), (e), (f) When the signal cables are run in parallel with or bundled with the power cables, magnetic and static induction noises may be propagated to the signal cables to cause malfunction of the devices and the following countermeasures must be taken:
• Install easily affected devices as far away as possible from the inverter. • Run easily affected signal cables as far away as possible from the inverter and its I/O cables. • Do not run the signal cables and power cables (inverter I/O cables) in parallel with each other and do not bundle them. • Use shielded cables as signal cables and power cables and run them in individual metal conduits to produce further effects.
(g) When the power supplies of the peripheral devices are connected to the power supply of the inverter in the same line, inverter-generated noises may flow back through the power supply cables to cause malfunction of the devices and the following countermeasures must be taken: • Install the line noise filter (FR-BLF or FR-BSF01) to the power cables (output cables) of the inverter. (h) When a closed loop circuit is formed by connecting the peripheral device wiring to the inverter, leakage currents may flow through the earthing (grounding) cable of the inverter to cause the device to malfunction.
In that case, disconnecting the earthing (grounding) cable from the device may stop the malfunction of the device.