MCCB MC Thermal relay Power supply Motor 1 Inverter M Line-to-line leakage currents path Line-to-line static capacitances 2 Countermeasure • If the carrier frequency setting is high, decrease the Pr.72 PWM frequency selection setting. • Use Pr.9 Electronic thermal O/L relay . 3 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 5 Installation and selection of the molded case circuit breaker to directly detect motor temperature.
Install a molded case circuit breaker (MCCB) on the power receiving side to protect the wiring at the inverter input side. Select 5 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 6 breaker, use the Mitsubishi earth leakage current breaker designed for harmonics and surge suppression.
Selecting the rated sensitivity current for the earth leakage circuit breaker 7 of the PWM carrier frequency. When using an earth leakage circuit breaker with the inverter circuit, select its rated sensitivity current as follows, independently • Breaker designed for harmonic and surge suppression Ig1, Ig2: Leakage currents in wire path during commercial power 8 Rated sensitivity current supply operation • Standard breaker I∆n ≥ 10 Ч (Ig1 + Ign + Igi + Ig2 + Igm) Ign: Leakage current of inverter input side noise filter Igm:
Leakage current of motor during commercial power supply 9 Rated sensitivity current operation I∆n ≥ 10 Ч {Ig1 + Ign + Igi + 3 Ч (Ig2 + Igm)} Example of leakage current of cable path per 1km during the commercial power supply operation when the CV cable is routed in metal conduit (200 V 60 Hz) Leakage current example of three-phase induction motor during the commercial power supply operation (200 V 60 Hz) Igi:
Leakage current of inverter unit Example of leakage current per 1km during the commercial power supply operation when the CV cable is routed in metal conduit Leakage current example of threephase induction motor during the commercial power supply operation 10 (Three-phase three-wire delta connection 400 V 60 Hz) (Totally-enclosed fan-cooled type motor 400 V 60 Hz) Leakage currents (mA) 100 120 Leakage currents (mA) 2. 0 Leakage currents (mA) 100 120 80 Leakage currents (mA) 0.2 0.3 0.5 0.7 1.0 2.0 60 80 0. 5 0. 7 1. 0 40 60 20 40 0. 2 0. 3 20 0 23.5 5.5 81422 30 38 60 80 100 150 0.1 1.5 3.7 2.2 7.5 3045 5.5 18.5 15223755 11 0 Cable size (mm ) 2 2 3.5 5.5 8 1422 30 38 60 80 100 150 0.
1 Motor capacity (kW) 1. 5 3. 7 2. 2 7. 5 1522 11 37 30 55 45 5.5 18. 5 For " " connection, the amount of leakage current is appox. 1/3 of the above value. Cable size (mm ) 2 Motor capacity (kW) Example 5.5mm 2 Ч5m 5.5mm 2 Ч50m ELB Noise filter Inverter M 3φ 200V2.2kW Ig1 Ign Ig2 Igm Igi 49 3.
PRECAUTIONS FOR USE OF THE INVERTER 3.1 Electro-magnetic interference (EMI) and leakage currents Item Breaker designed for harmonic and surge suppression Standard breaker eakage current Ig1 (mA) 5m 33 × = 0.17 1000m eakage current Ign (mA) 0 (without noise filter) eakage current Igi (mA) 1 eakage current Ig2 (mA) 50m 33 × = 1.65 1000m Motor leakage current Igm (mA) 0.18 otal leakage current (mA) 3.00 6.66 ated sensitivity current (mA) (≥ 10) Ig 30 100