SIKOSTARTTM 3RW34 - Siemens Industry, Inc.

Operating Principle4 Operating Principle4.1 Function Overview4.1.1 Soft Start with Coast to RestThe SIKOSTART 3RW34 soft starter utilizes a voltage ramp design to produce an output voltage to the motor thatincreases from a customer selected initial voltage to full line supply voltage over an adjustable starting time.The accelerating and coasting ramp times can be set independently.Fig. 5 shows the relationship of voltage and speed with respect to time when a soft start is used with coast to rest.The controller potentiometers have been set as follows:U m The initial voltage is set at approximately 30 %.t1 The start time setting is greater than 0.t2 The stop time is set at 0 which allows the motor to coast to a stop.EnglishMotor Voltaget1F 0U0F100%t2 = 0Time tMotor Speed100%0 t1FFU 0M Coil InputEnergizedt2 = 0Time tTime tFig. 5 : Voltage and time curves for soft start with coast to stop4.1.2 Soft Start with Soft StopFig. 6, like Fig. 5, shows the voltage and speed curves for a soft start but with controlled deceleration. Thepotentiometers have been set as follows:U m The initial voltage is set at approximately 30 %.t1 The start time setting is greater than 0.t2 The stop time setting is greater than 0 which allows the motor to soft stop.Motor VoltageFU0t10F100%0Ft2Time tMotor Speed0FU 0t1F100%0Ft2Time tM Coil InputEnergizedTime tFig. 6 : Voltage and Speed Curves for Soft Start with Soft Stop3ZX1012-0RW34-1AN1 5