Connecting The Motor To The Inverter In A Star Or Delta Connection - Siemens Sinamics G120 Hardware Installation Manual
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5.3
Connecting the motor to the inverter in a star or delta connection
Standard induction motors with a rated power of approximately ≤ 3 kW are normally
connected in a star/delta connection (Y/Δ) at 400 V/230 V. For a 400-V line supply, you can
connect the motor to the inverter either in a star or in a delta connection.
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 inverter must supply approximately 1.73x current. Select an inverter 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.
Power Modules PM240
Hardware Installation Manual, 07/2016, A5E36985441C AA
5.3 Connecting the motor to the inverter in a star or delta connection
In a star connection, the motor can provide its
rated torque M
quency f
Rated voltage U
rated frequency f
The motor goes into field weakening above
the rated frequency. In field weakening, the
available motor torque decreases linearly with
1/f. In field weakening, the available power
remains constant.
in the range 0 ... rated fre-
N
.
N
= 400 V is available at a
N
= 50 Hz.
N
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
available at a frequency of
f = √3 × 50 Hz ≈ 87 Hz.
Connecting-up
.
N
.
N
49
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