Mitsubishi Electric FR-D720-0.2K-G, Инструкция по эксплуатации

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EMC and leakage currents
3.1 EMC and leakage currents
3.1.1 Leakage currents and countermeasures
Static capacitance exists between the drive unit's I/O cables, other cables, and the earth, and in the motor. Because leakage
current flows through such static capacitance, take the following measures. Select an earth leakage circuit breaker according
to the rated sensitivity current of the leakage current breaker. Do not select it by the carrier frequency.
(1) To-earth (ground) leakage currents
Leakage currents may flow not only into the drive unit's own line but also into the other lines through the earthing (grounding)
cable, etc. These leakage currents may operate earth (ground) leakage circuit breakers and earth leakage relays
unnecessarily.
 Suppression technique
 Use an earth leakage circuit breaker with a weak sensitivity in the high frequency range.
The output current of the drive unit contains a high-frequency leakage current component, which gives relatively low
impacts to human bodies. The detention level for this high-frequency leakage current component can be set weaker to
prevent unnecessary operations.
 Minimize the to-earth stray capacitance.
Use the cables insulated with low dielectric constant material, and perform wiring to make the wiring length between the
drive unit and the motor to be as short as possible.
(2) Line-to-line leakage currents
Harmonics of leakage currents flowing in static capacitances between the drive unit output cables may operate the external
thermal relay unnecessarily.
 Measures
 Use Pr. 9 Electronic thermal O/L relay .
 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.
 Increase the external thermal overload relay setting by the amount of the leakage current.
 Minimize the stray capacitance between the lines.
Use the cables insulated with low dielectric constant material, and perform wiring to make the wiring length between the
drive unit and the motor to be as short as possible.
 Installation and selection of molded case circuit breaker
Install a moulded case circuit breaker (MCCB) on the power receiving side to protect the wiring of the drive unit input side.
Select the MCCB according to the drive unit input side power factor (which depends on the power supply voltage, output
frequency and load). Especially for a completely electromagnetic MCCB, one of 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 Electric earth leakage current breaker designed for harmonics and surge
suppression.
Power
supply
Thermal relay
Line-to-line static
capacitances
MCCB MC
Line-to-line leakage currents path
Motor
Drive unit
M