Direct Startup Mode; Motor Heating Startup Mode - Siemens 3RW44 Manual

7.2.5

Direct startup mode

If the "Direct" startup mode is set, the motor voltage is increased immediately to the level of
the supply voltage once the start command has been issued. This is equivalent to the start
behavior with a contactor, i.e. no limitation of the starting current and the starting torque.
Note
Due to the motor's high starting current, the "current limit exceeded" fault can occur in the
case of the "direct" startup mode. It may be necessary to select a larger soft starter.
Ramp-up detection
The soft starter features internal ramp-up detection. If a completed motor ramp-up is
detected, the internal bypass contacts close and the thyristors are bridged.
7.2.6

Motor heating startup mode

If IP54 motors are used outdoors, condensation forms in the motor when it cools down (e.g.
overnight or in the winter). This can result in leakage currents or short-circuits when the
motor is switched on.
To heat the motor winding, a pulsating direct current is injected into it.
When the "motor heating" startup mode is selected, a heating power can be entered in the
settings. This should be selected so that the motor is not damaged. The heating power
setting range is from 10 - 100 %. This corresponds to a comparable motor current of about
5 - 30 % of the rated motor current.
Typical applications for motor heating
For example, used for drives outdoors to minimize condensation inside the motor.
May lead to damage to property.
The motor heating startup mode is not a continuous operating mode. The motor must be
equipped with a temperature sensor (Thermoclick/PTC) to ensure motor protection. The
motor model with integrated electronic motor overload protection is not suitable for this kind
of operation.
3RW44 soft starters
Manual, 03/2017, NEB535219502000/RS-AB/008
CAUTION
Device functions
7.2 Startup modes
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