Operating Principle; Function Overview; Soft Start With Coast To Rest; Soft Start With Soft Stop - Siemens SIKOSTART 3RW34 Instructions De Service

4

Operating Principle

4.1

Function Overview

The SIKOSTART 3RW34 soft starter utilizes a voltage ramp design to produce an output voltage to the motor that
increases 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.

4.1.1 Soft Start with Coast to Rest

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
t1
t2
Motor Voltage
Motor Speed
M Coil Input
Fig. 5 : Voltage and time curves for soft start with coast to stop

4.1.2 Soft Start with Soft Stop

Fig. 6, like Fig. 5, shows the voltage and speed curves for a soft start but with controlled deceleration. The
potentiometers have been set as follows:
U
m
t1
t2
Motor Voltage
Motor Speed
M Coil Input
Fig. 6 : Voltage and Speed Curves for Soft Start with Soft Stop
3ZX1012-0RW34-1AN1
The initial voltage is set at approximately 30 %.
The start time setting is greater than 0.
The stop time is set at 0 which allows the motor to coast to a stop.
100%
t1
F
0
t2 = 0
U
F
0
Time t
100%
0
t1
t2 = 0
F
F
U
0
Time t
Energized
Time t
The initial voltage is set at approximately 30 %.
The start time setting is greater than 0.
The stop time setting is greater than 0 which allows the motor to soft stop.
100%
t1
F F
0
U
t2
F
0
0
Time t
100%
F
0
t1
t2
F
0
F
U
0
Time t
Energized
Time t
Operating Principle
5