Technical Specifications

FAQ

1. What is the main function of the ABB PSTX720-600-70 soft starter?
The ABB PSTX720-600-70 is a high-power three-phase soft starter designed to control motor acceleration and deceleration. It gradually applies voltage to the motor during starting, helping reduce inrush current and mechanical stress. It also supports controlled soft stopping through voltage or torque ramp control. With a rated operational current of 720 A and a main circuit voltage range of 208–600 V AC, it is designed for medium- to large-sized industrial motors.

2. What motor applications are suitable for the PSTX720-600-70?
The PSTX720-600-70 is suitable for demanding industrial applications involving large three-phase motors. Typical applications include pumps, fans, compressors, conveyors and other high-power motor-driven equipment. The soft starter is particularly useful where direct-on-line starting could produce excessive current, mechanical shock or process disturbances. The correct configuration should be selected according to the motor’s rated current, load characteristics and starting requirements.

3. What is the rated current of the PSTX720-600-70?
The rated operational current for an in-line connection is 720 A. The device also supports an inside-delta connection, where the rated operational current can reach 1247 A. The actual motor current setting should be configured according to the motor nameplate and application rather than simply using the maximum soft starter rating. Correct configuration is important for the built-in electronic overload and motor protection functions.

4. Does the PSTX720-600-70 support inside-delta connection?
Yes. The PSTX720-600-70 supports both conventional in-line connection and inside-delta connection. With an inside-delta arrangement, the soft starter is connected within the motor’s delta circuit, allowing a higher motor current rating relative to the device’s in-line rating. Proper motor winding configuration, wiring and parameter settings are essential when using this connection method.

5. What protection functions are included in the PSTX720-600-70?
The PSTX720-600-70 includes built-in electronic overload protection and a range of motor and application protection functions. These include current limiting, kickstart, motor heating, pump cleaning, diagnostics and other protective or control functions. The available protection features help manage abnormal motor conditions and adapt the starter to different industrial loads. Protection parameters should be configured according to the motor and driven equipment.

6. What communication options are available on the PSTX720-600-70?
The PSTX720-600-70 includes built-in Modbus RTU communication. It can also be integrated with other industrial communication networks through optional fieldbus modules, including PROFINET, PROFIBUS, Modbus TCP and EtherNet/IP. Hardwired Start, Stop and Fault Reset signals are also supported, together with programmable digital inputs. This allows the soft starter to be integrated into PLC, DCS and other industrial automation systems.

7. What is the purpose of the built-in bypass function?
The built-in bypass allows the soft starter to bypass its semiconductor power components once the motor has reached normal operating conditions. This reduces power losses and heat generation during continuous motor operation while simplifying the overall installation. The bypass function also supports energy-efficient operation and reduces the need for a separate external bypass contactor in applications where the integrated function is suitable.

8. What are common causes of PSTX720-600-70 starting faults?
Common causes include incorrect motor-current settings, excessive starting load, insufficient supply voltage, unsuitable starting parameters, incorrect control wiring, excessive starting frequency and motor or mechanical problems. A load requiring excessive starting torque can also cause the current limit to be reached or activate protective functions. During troubleshooting, check the motor nameplate data, configured current, incoming power, control signals, starting ramp, current limit and mechanical load. The soft starter’s diagnostic information should also be reviewed before changing operating parameters.