July 2013 7.7 Special functions 1103
7.7.6 Peculiarities in weakened-field operation
Reduction of the
magnetization
current
Some of the asynchronous spindle motors require a high magnetizing current
at low speeds (n < n
field weakening
). This magnetizing current can, however,
lead to thermal motor problems at the rpm for field weakening n
FW
when
there is no load.
The nominal voltage (and so also the nominal magnetization current) at the
rpm for field weakening n
FW
when there is no load can be reduced with
MP2210.x. The entered reduction results in a nominal voltage curve as shown
in the figure below. The maximum nominal voltage is reached when
n=3·n
field weakening
. The nominal voltage can be reduced by max. 60 %
(MP2210.x = 60).
If a load is placed on the drive, then the nominal voltage is increased again
automatically in order to improve the dynamics.
MP2210.x Reduction of the nominal voltage at the rpm for field
weakening when there is no load
Input: 0 to 60 [%]
0: Function inactive
Setting the
reduction of the
magnetization
current
If thermal problems arise on an asynchronous spindle with no load during
weakened-field operation, and these problems cannot be traced to an overload
or other mechanical problems, then please reduce the magnetization current
as follows:
Reduce the nominal voltage in steps of 10 % in MP2210.x.
Reduce MP2210.x until a stable temperature within the motor specifications
is reached when there is no load.
n
3 · n
FW
n
FW
MP2210.x
U
nominal
Please note that the reduction of the magnetization current can lead to a
limitation of the drive’s dynamics. However, this depends on the drive, and
must be judged separately in each case.
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