Installation
4.2 Electrical Installation
Converter with the control units CU240D-2
60
Operating Instructions, 04/2018, FW V4.9 SP10, A5E34262100B AF
Operating the motor in a star connection
In a star connection, the motor can provide its
rated torque M
N
in the range 0 … rated fre-
quency f
N
.
Rated voltage U
N
= 400 V is available at a
rated frequency f
N
= 50 Hz.
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.
Operating the motor in a delta connection with 87 Hz characteristic
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
N
.
The maximum voltage U = 400 V is
available at a frequency of
f =
√3
× 50
Hz ≈ 87
Hz.
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
N
.
●
As the fan impeller rotates faster, the motor has a higher noise level than operation with
f
≤
50 Hz.
