Semiconductor soft starter 3RW3 Starting voltage The starting voltage should be set so that the motor starts up swiftly. Ramp time The ramp time should be set so that the motor can start within this time. If the star time of a star-delta start is known, the ramp time can be set to this value. Coasting time The duration of the voltage ramp during coasting is set with the "coasting time" potentiometer. This can be used to achieve an extension of coasting in comparison with free coasting If the value is set to 0, coasting is free.
Switching frequency To avoid thermal overloading of the units, it is imperative to keep to the max- imum permitted switching frequency and compensation factor tables (see assembly guidelines in Ch. 8.3.2). Starting time To arrive at optimum operating conditions for the soft starter 3RW3, the set starting time should be approximately 1 s longer than the resulting motor starting time to ensure that the internal bypass contacts will not be loaded with the starting current. This protects the internal bypass contacts and increases their useful life. Longer starting times increase the thermal load on the units and the motor, leading to a reduction in the permissible switch- ing frequency.
Locations of the con- necting terminals 3RW30 The following depiction shows the positions of the connection terminals and of the adjustment potentiometers. Size S00 3RW301. Size S0 to S3 3RW302./303./304. 1 L1 3 L2 5 L3 IN1 A1 1 L1 3 L2 5 L3 A1 A2 1 3RW 5 10 20s 0 5 10 max min 5 20s 0 max min 5 10 20s 0 10 13 14/23 24 20s 0 Fig. 8-18: Locations of connecting terminals and of adjusting potentiometers 2 T1 4 T2 6 T3 A2 2 T1 4 T2 6 T3 3RW31 The soft starter 3RW31 is available in size S0. Externally, the difference with respect to the 3RW30 consists of the marking of the contacts and of the terminals: The "BYPASSED" - auxiliary contact does not exist.
The free contact is used to enable the necessary cycling contact IN2 to switch between the two ramp times t R1 and t R2 . The 3 RW31 does not have a coasting ramp. The adjustment potentiome- ter with which the coasting time is set on the 3RW30 serves here to set the second ramp time t R2 . The "ON" auxiliary contact does not exist 8-30 Stand 08/99