Power Wiring; Power Circuit Connection; Safety Instructions; Rules For Emc Compliant Motor - Inverter Wiring - Siemens S120 Instructions Manual

7 POWER WIRING

7.1

POWER CIRCUIT CONNECTION

All electrical wirings have to be done, respecting the rules shown in the table below:
U1,V1,W1 Mains power supply input
U2;V2;W2 Inverter output
R1;R2 External braking resistor
Earth
7.2

SAFETY INSTRUCTIONS

1- Do not power the inverter without first making the earth connection.
2- To increase inverter protection (especially against overvoltage due to electrical storms), three
extrafast-blow fuses (one for each phase) can be installed in series with the supply mains input
terminals. The fuses must be rated according to the various sizes. The set of fuses, complete with
protection box, can be supplied on request (not indispensable!).
3- To avoid permanently damaging the inverter, do not connect braking resistors with resistance or
power ratings lower than those given in the table (see) .
4- The inverter drive must be connected "upstream" of the power contactors.
5- The external braking resistor heats up during operation. Do not install it near or in contact with
inflammable materials; protect it to prevent direct contact.
6- Wire earth connections and masses correctly to avoid problems of EMC interference.
7- Pay particular attention to the power connection; if the input and output are inverted, the
inverter will inevitably be damaged.
7.3

RULES FOR EMC COMPLIANT MOTOR - INVERTER WIRING

For a correct wiring of the group INVERTER - ENGINE, in addition to the procedure described in Chapter 4,
about electromagnetic compatibility, follow the steps below:
1- The inverter and motor must be connected directly to the building's earth system.
2- The power cables for the inverter/contactors and contactors/motor connection must be as short as
possible, shielded four-core (three phases plus yellow/green earth wire), or four unshielded cables
bound together and inserted in a raceway or a metal pipe connected to earth. In other words, there
must be an earth wire as close as possible to the power wires in the same cable or in the same pipe.
If shielded cable is used, continuity of the earth braid between the inverter/contactors and
contactors/motor section must be ensured.
It is advisable to connect the shielding to earth at both ends by means of a U-clip or with special
terminals.
If the shield cannot be connected with a U clip inside the motor terminal block, it must be earthed on
the frame before entering the terminal block.
3- Even if it is not essential, a good engineering way provides to have a shielded cable also in the
power line in input, in order to prevent that irradiated noises are brought out, by means this cable.
4- The inverter power cables (input and output) and control cables must be kept as far apart as
possible and must not run parallel, even if shielded; if the cables cross, they must be arranged at an
angle of 90°.
5- Irrespective of the connection to the building's earth system, the motor frame MUST be connected to
the cable shield and to the yellow/green earth wire inside the shielded cable.
6- The inverter emits radiated interference, which can therefore be picked up and carried outside the
panel by the cables, especially by flexible cables which radiate the interference into the lift shaft. If
this problem is to be avoided, the connections between the panel and the inverter must be made
using shielded wires with shield connected to earth at both ends. Shielded cables must not be used
without the shield connected to earth, as in this case any interference will be greater than with an
unshielded cable.
Any free or unused wires in a multicore cable must be connected to earth at both ends.
Siemens S120_EN_rev06-08062017.docx
Connect the mains power supply input phases in any order.
Connect the three output phases to the contactors, then to
the motor.
Connect the external braking resistor
Connect to the building's earth system.
7-1