SIEMENS
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Siemens CR 1 · 2015
6
Drive systems
SIMOTRAS HD AC power controller
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Configuration
Notes on configuration
Rated current of the device
I
rated
In crane operation, the motors are not operated continuously, but
with variable load, at varying speeds, and with different ON du-
rations. Under these conditions, it is sufficient when the rated
current for the device
I
rated
is greater than the motor rated cur-
rent. In intermittent duty with appropriate pauses in operation,
the devices can carry twice the rated device current of
I
rated
gre-
ater than the rated motor current for 20 s. In intermittent duty with
appropriate pauses in operation, the devices can carry twice the
rated device current of
I
rated
for 20 s. This covers all the normal
acceleration situations that occur with cranes. The SIMOTRAS
HD devices can be operated continuously at the rated current
for the device
I
rated
; the limit temperature for the thyristors will,
however, be reached. Acceleration is not permitted from this
operating state since the thyristors could be overloaded.
Rotor contactors
To ensure a reliable ramp-up from the closed-loop control
characteristic to rated speed, it is recommended that 4 rotor
contactors are used. Activation of the rotor contactors through
contactor relays.
Permissible ON duration
Under unusual operating conditions, such as traversing with full
load at extremely low speed for a long time, motors, resistors
and SIMOTRAS HD must be dimensioned appropriately. When
phase angle control is used, a higher stator current flows to
achieve the necessary torque due to the reduced magnetization.
The motors may become thermally overloaded, because the
thermal power losses rise with the quadrant of the current. The
resistors are overloaded when the closed-loop control characte-
ristic is traversed for an extended period.
Rotor resistances
Since the speed is influenced with additional rotor resistors, the
rotor performance is largely converted into heat in the external
resistor. This ensures that excessive heating of the motor is avo-
ided when traversing at low speed over long periods.
Emergency or safety limit switch
Due to the lack of stator contactors, the motor can no longer be
galvanically isolated from the AC power controller, e.g. when an
operational limit switch is actuated. If the controller is then not
able to block the thyristors due to a device fault, this could result
in an impermissible operating state.
It is therefore recommended that emergency or safety limit swit-
ches are used. These respond when the operational limit switch
is passed and act on a line contactor or the crane switch.
© Siemens AG 2015