Safe stop
Instruction handbook
b maXX
BM4400, BM4600, BM4700
Document No.: 5.12008.07
329
E
NOTE
At total failure of an internal driver (IGBT) or an control element, it can trigger a tem-
porary excitation of the drive (also in the STO state).
If the link to a winding of the motor is „short-circuited“, a magnetic field develops in
the motor. If this is an asynchronous motor, the generated DC field cannot effect a
movement of the rotor.
The rotor in a permanently energized synchronous motor will rotate into a notch po-
sition. The angular movement depends on the rotor position and the number of pole
pairs of the motor. It amounts to a maximum of 180°/number of pole pairs.
The possible movement must be considered, if a machine with a synchronous motor
is developed.
NOTE
The function is limited to the prevention of an unexpected starting. The switching of
the safety relay, while the rotor of the motor is rotating, causes an uncontrolled
„coasting“ of the machine. Braking with the converter is not possible.
DANGER!
Danger to life by electrical current!
Power supply voltage can be present at the motor and at the device, if STO / Safe
stop function is active.
Therefore:
m
De-energize the device, as it would be done with a device without safety relay. The
device and the motor is
not
de-energized by the safety relay!
NOTE
There is no isolation from the supply system if the function STO/Safe stop is activat-
ed. There can be potential at the converter and at the motor. In the case of mainte-
nance-, service- and repair- works on electrical components of the drive system,
protection against dangers must be provided by other means (e. g. main switch).
Summary of Contents for b maxx BM4400
Page 359: ......
