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Variable frequency drive Mains Connection

  • Disconnect the variable frequency drive from mains voltage and protect it against being energized unintentionally.
  • Verify that the variable frequency drive is discharged.
  • Wait for some minutes until the DC link capacitors have discharged before starting to work at the unit.
  • When the variable frequency drive is disconnected from power supply, the mains, DC-link voltage and motor terminals may still be live for some time.
The mains fuses and cable cross-sections are to be selected according to EN 60204-1 and DIN VDE 0298 Part 4 for the nominal operating point of the variable frequency drive. According to UL/CSA, approved Class 1 copper lines with a temperature range of 60/75°C and matching mains fuses are to be used for the VFD power cables. The electrical installation is to be done according to the variable frequency drives specifications and the applicable standards and directives.

The control, mains and motor lines must be kept physically separate from one another. The cables connected to the variable frequency drives may not be subjected to high-voltage insulation tests unless appropriate circuitry measures are taken before.
Variable frequency drive connection with fuses
Dimensioning of conductor cross-section
The VFD cable dimensions must be selected according to the current load and voltage drop to be expected.
Select the VFD cable cross-section of the cables such that the voltage drop is as small as possible. If the voltage drop is too great, the motor will not reach its full torque.
Comply with any additional national and application-specific regulations and the separate UL instructions.

Select cross-sections of PE conductor according to EN61800-5-1:
Mains cable
Protective conductor
Mains cable up to 10 mm²
Install two protective conductors of the same size as the mains cable, or one protective conductor of a size of 10 mm².
Mains cable 10…16 mm²
Install one protective conductor of the same size as the VFD mains cable.
Mains cable 16…35 mm²
Install one protective conductor with a cross-section of 16 mm².
Mains cable > 35 mm²
Install one protective conductor of half the size of the VFD mains cable.

Typical cross-sections
The following table provides an overview of typical variable frequency drives cable cross-sections (copper cable with PVC insulation, 30 °C ambient temperature, continuous mains current max. 100% rated input current). Actual cable cross-section requirements may deviate from these values due to actual operating conditions.

Three-phase connection (L1/L2/L3), 380 V
Mains cable
Motor cable
0,37 kW
0.75 kW
1.5 kW
2.2 kW
4.0 kW
1.5 mm²
2x1.5 mm² or 1x10 mm²
1.5 mm²
5.5 kW
7.5 kW
2.5 mm²
2x2.5 mm² or 1x10 mm²
2.5 mm²
11.0 kW
4 mm²
2x4 mm² or 1x10 mm²
4 mm²

Please note, that the mentioned typical cross sections do not consider other factors like fuses. Comply with applying local standards and applying branch standards.

Connection to IT mains
For connection to IT mains, pull out the plug-type jumper.
Connection to IT mains
Note: Removing the jumper reduces interference immunity and increases the emitted interference. Interference immunity can be increased by means of external filters. Additional work for EMC conformity may be possible. Comply with the EMC information.

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