Soft Starters work with 3-phase asynchronous motors.

Press Release Summary:

Sirius 3RW40 and 3RW44 enable gentle starting of 3-phase asynchronous motors and include integral bridging contact system and motor protection with adjustable overload tripping times. Sirius 3RW40 (2-phase) suits starting applications without step changes in torque and has output range from 75-250 kW at 400 V. Suited for drives with outputs up to 710 kW at 400 V, Sirius 3RW44 offers torque control, creep-feed function, diagnostic capabilities and graphical interface.

Original Press Release:

Gentle Start into the Day

Two new types of soft starters are being demonstrated by Siemens Automation and Drives (A&D) at the Hanover Fair in compact Sirius design for gentle starting of three-phase asynchronous motors to protect the load and the supply system. The new Sirius 3RW40 soft starters for standard applications supplement the two-phase-controlled Sirius 3RW30 in the output range up to 250kW. For difficult starting and stopping conditions, the new Sirius 3RW44 soft starter is ideal with its high functionality and graphical display. Soft starting is implemented with a torque control and there is a new brake function for quick stopping of driving loads. Both soft starters have an integral bridging contact system. This maintains the power losses of the soft starters at a negligible level preventing a rise in temperature of the air surrounding the controlgear.

The integral motor protection in the starters with adjustable overload tripping times (Class times) makes an overload relay superfluous, saves space in the control cabinet and saves additional wiring costs in the load feeder. A defect in the power section due to thermal overloading of the thyristors or a short-circuit is prevented by the internal device self-protection and by optional semiconductor protection fuses of the Sitor type. The control voltage wiring is connected through a removable terminal system and to protect personnel from touching the main supply terminals, terminal covers are available in the Sirius range.

The two-phase Sirius 3RW40 soft starter for starting applications without step changes in torque has an output range from 75 to 250kW at 400V and an overall width of 160mm maximum. For motor starting and stopping, it has a parameterizable voltage ramp and an adjustable current limiting function.

For the most demanding motor starting applications, the Sirius 3RW44 soft starter offers a high degree of functionality and diagnostic possibilities with convenient operator interfaces. Quick and easy start-up is possible using a keypad with a menu-driven graphical display. When the control voltage is applied, measurement and operational values as well as warning and fault messages are continuously output in the display. As an option, an external display module can be connected to the soft starter with a connecting cable to display the current messages on a control cabinet door. For integration into an automation system, the 3RW44 can be retrofitted with an optional PROFIBUS DP module.

For difficult starting and stopping procedures for drives with outputs up to 710kW at 400V in standard connection or up to 1200kW at 400V in root-3 connection, the 3RW44 soft starter has a new torque control. For positioning and calibration tasks, a creep-feed function is available. This can be used with reduced torque and adjustable lower speed to control the motor in both directions of rotation. The soft stopping and pump stop functions are also implemented using a torque control. Sudden water pressure as a result of immediate switch-off of a pump is prevented. Hydraulic disturbances such as noises and damage to the pipe system are avoided.

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