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The ABB PSTX720-600-70 1SFA898118R7000 PSTX Series Softstarter is a high-power motor starting and stopping device for three-phase AC motor applications. It controls the voltage applied to the motor during starting and stopping, reducing the mechanical and electrical stresses associated with direct-on-line starting.
The softstarter is suited to applications where large motors drive pumps, fans, compressors, conveyors, and other heavy-duty machinery. Instead of applying full motor voltage immediately, the PSTX control sequence gradually increases the motor supply during acceleration. This helps reduce starting current and allows the driven equipment to reach operating speed more smoothly.
During stopping, controlled voltage reduction can also reduce abrupt changes in motor torque. This is particularly useful for pump systems where sudden stopping can contribute to hydraulic disturbances, as well as conveyor and material-handling systems where uncontrolled deceleration can create mechanical shock.
The PSTX720-600-70 belongs to ABB’s PSTX Series and can be incorporated into motor control architectures alongside contactors, circuit protection, overload protection, bypass arrangements, control devices, and plant automation systems. For replacement work, the complete order code 1SFA898118R7000 should be matched with the existing motor rating, supply arrangement, control circuit, and application requirements.
| Parameter | Specification |
|---|---|
| Model | PSTX720-600-70 |
| Order Number | 1SFA898118R7000 |
| Product Family | PSTX Series |
| Product Type | Softstarter |
| Manufacturer | ABB |
| Primary Function | Controlled motor starting and stopping |
| Typical Application | Three-phase AC motor control |
| System Role | Motor starting and stopping control |
| Dimensions | 493 × 369 × 435 mm |
| Weight | 46.5 kg |
The PSTX softstarter controls the voltage supplied to the motor during the starting sequence. Semiconductor switching elements regulate the effective motor voltage so that the motor develops torque progressively rather than receiving full supply voltage instantaneously.
Three-Phase Supply → PSTX720-600-70 → Controlled Motor Voltage → Motor Acceleration → Full-Speed Operation
During startup, the softstarter increases the motor voltage according to the configured starting parameters. The motor accelerates progressively as the applied voltage and resulting torque increase. This reduces the abrupt current and torque transition normally associated with direct-on-line starting.
During stopping, the softstarter can reduce the applied motor voltage in a controlled sequence. The resulting reduction in motor torque allows the driven machine to decelerate more smoothly, which can be valuable in applications where sudden stopping creates mechanical or process disturbances.
The softstarter therefore operates between the incoming power system and the motor, while the external control system determines when the motor should start or stop.
The PSTX720-600-70 forms the motor-starting control layer between the incoming three-phase supply and the motor. It works together with protection, switching, control, and automation components to provide a controlled motor-starting arrangement.
PLC / Control System → PSTX Control Input → PSTX720-600-70 → Three-Phase Motor → Mechanical Load
| System Element | Function |
|---|---|
| PLC / Control System | Generates motor start and stop commands |
| Circuit Protection | Protects the motor circuit and associated equipment |
| Main Contactor | Provides system-level power switching |
| PSTX720-600-70 | Controls motor starting and stopping |
| Motor | Converts electrical energy into mechanical power |
| Pump / Fan / Conveyor | Represents the driven mechanical load |
| HMI / Supervisory System | Provides operator control and status monitoring |
| Application | Typical Use |
|---|---|
| Pump Systems | Smooth starting and controlled stopping of large pumps |
| HVAC / Industrial Fans | Reduced starting stress for high-power fan motors |
| Compressors | Controlled acceleration of compressor drive motors |
| Conveyors | Reduced mechanical shock during motor startup |
| Material Handling | Controlled acceleration of heavy loads |
| Industrial Machinery | Motor starting where direct-on-line starting is undesirable |
| Process Plants | Controlled motor operation in continuous processes |
| Component | Function |
|---|---|
| Three-Phase AC Motor | Main motor controlled by the softstarter |
| Circuit Breaker / Protection Device | Provides upstream circuit protection |
| Main Contactor | Provides isolation and switching of the motor circuit |
| Motor Protection Device | Protects the motor against applicable overload conditions |
| PLC | Generates automatic motor control commands |
| HMI | Provides operator control and motor status information |
| Bypass Contactor | Can provide an alternative current path during normal running where the system configuration requires it |
| Motor Cable | Connects the softstarter to the motor |
| Model / Product Family | Product Type | Typical Application |
|---|---|---|
| ABB PSTX720-600-70 | PSTX Series Softstarter | High-power motor starting and stopping |
| ABB PSTX Series | Softstarter Family | Industrial motor control |
| ABB PSTX Softstarter Family | Motor Softstarter | Pumps, fans, compressors, and conveyors |
| ABB PSE Series | Softstarter | Compact motor starting applications |
| ABB PSR Series | Softstarter | Compact motor starting and stopping |
| ABB AF Series | Contactor | Motor switching and control |
| ABB MS Series | Motor Protection Device | Motor circuit protection |
| ABB Tmax Series | Circuit Breaker | Industrial power circuit protection |
A direct-on-line starter applies the available motor supply essentially immediately, resulting in high starting current and a rapid torque transition. The PSTX720-600-70 regulates the motor voltage during starting and stopping, allowing acceleration and deceleration to be controlled more gradually.
Controlled acceleration and stopping can reduce abrupt changes in motor torque and pump operation. In suitable pump applications, this can help reduce mechanical stress and process disturbances associated with sudden motor starting or stopping.
Check the configured starting parameters, incoming three-phase supply, motor connections, protection devices, control commands, and mechanical load. If the motor reaches a certain speed and then stalls or trips, the motor load and available starting torque should also be investigated.
The softstarter and contactor perform different functions. The PSTX controls the motor starting and stopping process, while contactors and protective devices may still be required depending on the motor-control architecture, isolation requirements, bypass arrangement, and applicable installation standards.