Connecting The Motor To The Converter In A Star Or Delta Connection - Siemens SINAMICS G120C Operating Instructions Manual

4.9.8

Connecting the motor to the converter in a star or delta connection

Overview
Standard induction motors up to a rated power of approximately 3 kW are usually connected in
star/delta connection (Y/Δ) at 400 V/230 V. For a 400‑V line supply, you can connect the motor
to the converter either in a star or in a delta connection.
Function description
Operating the motor in a star connection
Operating the motor in a delta connection with 87 Hz characteristic
The motor only goes into field weakening above 87 Hz.
The higher motor power when operated with an 87 Hz characteristic has the following
disadvantages:
• The converter must supply approximately 1.73x current. Select a converter based on its rated
current - and not its rated power.
• The motor temperature increases more significantly than when operated with f ≤ 50 Hz.
• The motor must have windings that are approved for a voltage > rated voltage U
• As the fan impeller rotates faster, the motor has a higher noise level than operation with
f ≤ 50 Hz.
SINAMICS G120C Converters
Operating Instructions, 02/2023, FW V4.7 SP14, A5E34263257B AK
4.9 Connect the line supply, motor and braking resistor
In a star connection, the motor can provide its
rated torque M
quency f .
N
Rated voltage U
frequency f = 50 Hz.
N
The motor goes into field weakening above the
rated frequency. In field weakening, the avail‐
able motor torque decreases proportionally
with 1/f. In field weakening, the available pow‐
er remains constant.
In a delta connection, the motor is oper‐
ated with a voltage and frequency above
its rated values. As a consequence, the
motor power is increased by a
factor √3 ≈ 1.73.
In the range f = 0 ... 87 Hz, the motor can
output its rated torque M
The maximum voltage U = 400 V is avail‐
able at a frequency of f = √3 × 50 Hz ≈
87 Hz.
Installing
in the range 0 ... rated fre‐
N
= 400 V is available at a rated
N
.
N
.
N
81