Product Overview

The ABB PST85-600-70 1SFA894008R7000 Soft Starter is an advanced motor-starting and stopping device designed for three-phase AC motors in industrial applications. Part of ABB’s PST softstarter family, it helps control motor acceleration and deceleration by regulating the voltage supplied to the motor during starting and stopping.

Direct-on-line motor starting can produce high inrush current and sudden mechanical torque. These effects may place additional stress on electrical distribution systems, motors, couplings, belts, pumps, and other driven equipment. A soft starter reduces these effects by increasing the motor voltage progressively during startup.

The PST85-600-70 supports main-circuit operating voltages from 208 to 600 V AC and uses a 100–250 V AC control supply. Its rated operational current depends on the connection method: 85 A for in-line connection and 147 A for inside-delta connection. At 400 V, the corresponding motor power ratings are 45 kW and 75 kW respectively.

The PST series is designed for industrial motor applications requiring controlled starting, stopping, and motor protection. The PST85 includes electronic overload protection, adjustable starting parameters, current limitation, signal relays, and analog output functions. These features allow it to work with motor control panels, PLC systems, and other industrial automation equipment.

The soft starter can be used in applications such as pumps, fans, compressors, conveyors, and general-purpose industrial machinery. Its suitability depends on the motor’s rated current, starting conditions, load characteristics, and the selected connection method.

Technical Specifications

Note: The supplied dimensions and weight are retained as listing parameters. ABB’s product catalog lists approximately 11.2 kg for this PST85 rating, so verify the actual unit weight and whether packaging is included.

Function and Working Principle

The PST85-600-70 controls the voltage applied to a three-phase motor during startup and stopping. Instead of applying full voltage immediately, the soft starter gradually increases the motor voltage according to configured ramp and starting parameters.

This controlled transition helps reduce electrical and mechanical stress in motor-driven equipment.

1. Soft Starting

When a motor starts directly across the line, it can draw a high inrush current. The PST85 limits the starting impact by controlling the voltage applied to the motor.

The initial voltage and ramp time can be adjusted to match the motor and load. This helps the motor accelerate more smoothly and can reduce sudden torque changes in the driven machinery.

2. Controlled Stopping

The PST85 also supports controlled stopping. Rather than simply removing power immediately, the soft starter can reduce the motor voltage according to a configured stopping ramp.

This function is particularly useful in applications where abrupt stopping may cause hydraulic or mechanical problems. For example, controlled stopping can help reduce pressure disturbances in certain pumping systems.

The stopping behavior must be selected according to the motor and process requirements. A soft starter does not provide the same speed-control capability as a variable frequency drive.

3. Current Limitation

The device includes an adjustable current-limit function. The current limit can be configured within the specified range of 1.5–7 times the rated operational current.

This allows engineers to balance starting torque and electrical demand. A lower current limit may reduce the impact on the power supply, but it must still provide enough torque to accelerate the connected load.

4. Electronic Motor Overload Protection

The PST85 includes integrated electronic overload protection. The motor current setting can be adjusted to suit the connected motor.

Correct configuration is essential. The overload setting should be based on the motor nameplate and the applicable protection requirements rather than simply using the soft starter’s maximum current rating.

5. Monitoring and Signal Outputs

The soft starter provides relay signals and analog output options for system monitoring. Depending on the configuration, these signals can be used to communicate operating status, fault conditions, or measured values to a PLC or other control equipment.

These functions support maintenance and process supervision by making relevant operating information available to the wider control system.

Role in Industrial Control Systems

The ABB PST85-600-70 can operate as part of a motor control center or industrial automation cabinet. It manages motor starting and stopping while coordinating with upstream protection devices, contactors, PLCs, and operator interfaces.

PLC Integration

A PLC can control the soft starter through suitable control signals and monitor its status through relay outputs or supported communication interfaces.

For example, a PLC may issue a start command when a tank level reaches a defined point. The PST85 then performs the configured motor-starting sequence. When a process condition changes, the PLC can initiate a stop command.

The actual integration method depends on the control terminals, selected communication accessories, and system design.

HMI and Operator Monitoring

An HMI can display motor operating status, start and stop conditions, and fault information collected through the PLC or supported communication arrangement.

Operators can use this information to identify abnormal conditions and coordinate equipment operation with the production process.

Motor Protection Coordination

The PST85’s electronic overload protection forms part of the motor protection strategy. It must be coordinated with upstream short-circuit protection and other electrical protection devices.

A complete motor starter assembly may also include a circuit breaker or fuses, isolation equipment, contactors, and terminal components selected according to the installation requirements.

Industrial Applications

The PST85-600-70 is designed for industrial three-phase motor applications. Its current and power ratings allow it to be considered for medium-capacity motor installations when the operating conditions match the soft starter’s specifications.

1. Industrial Pump Systems

Pumps are frequently started and stopped in water treatment, manufacturing, building services, and process industries.

A soft starter can reduce the mechanical impact associated with motor startup. Its controlled stopping function may also help reduce pressure changes in suitable pumping applications.

The actual ramp settings should be selected according to pump type, pipeline conditions, fluid characteristics, and process requirements.

2. Industrial Fans and Blowers

Large ventilation and process-air systems may experience substantial mechanical stress during direct motor starting.

The PST85 can provide a controlled starting sequence for compatible fan motors. This helps reduce abrupt torque changes and can support smoother equipment operation.

3. Air Compressors

Industrial compressors often require reliable motor starting under demanding operating conditions. A soft starter can help manage starting current and mechanical stress when used with a compatible compressor design.

The compressor manufacturer’s starting requirements must be checked carefully. Some compressor systems require specific unloading or pressure-release sequences before motor startup.

4. Conveyor Systems

Conveyors used in manufacturing, packaging, and material handling may carry products or materials that can shift when the motor starts abruptly.

A soft starter provides a gradual acceleration profile, helping reduce sudden mechanical movement. It is suitable for applications where controlled starting and stopping are sufficient and continuous variable-speed operation is not required.

5. Industrial Processing Machinery

The PST85 may also be used with mixers, auxiliary machinery, and other motor-driven equipment. Engineers should evaluate the motor’s starting torque, load inertia, number of starts per hour, and duty cycle before selecting the soft starter.

Installation and System Integration

Correct installation is important for electrical safety, motor protection, and reliable operation.

1. Verify Main Circuit Voltage

Confirm that the incoming supply falls within the PST85’s rated main-circuit voltage range of 208–600 V AC.

Check the motor voltage, rated current, frequency, and connection arrangement before installation. The selected in-line or inside-delta configuration affects the applicable current and power ratings.

2. Confirm Control Supply

The PST85 requires a control supply within the specified 100–250 V AC range. Its control circuit also supports 24 V DC operation as specified for the product.

The control supply and control wiring should be checked against the terminal diagram and installation manual. Do not assume that all control terminals use the same voltage.

3. Select the Correct Connection Method

The soft starter supports both in-line and inside-delta connection arrangements.

• In-line connection: The soft starter is installed in series with the motor supply conductors. Its rated current for this model is 85 A.
• Inside-delta connection: The soft starter is connected within a compatible motor delta circuit. Its rated current is 147 A.

Inside-delta installation requires a motor with suitable winding connections and an appropriately designed circuit. The wiring diagram and protection requirements must be followed carefully.

4. Configure Motor Parameters

Set the rated motor current and starting parameters according to the motor nameplate and load requirements.

Important settings include:

• Motor rated current.
• Initial starting voltage.
• Starting ramp time.
• Stopping ramp time.
• Current limit.
• Overload protection parameters.

Incorrect settings may result in excessive starting time, insufficient starting torque, nuisance trips, or inadequate motor protection.

5. Coordinate Protection Devices

The soft starter should be installed with suitable upstream short-circuit protection and isolation equipment. The selection of fuses or circuit breakers must follow ABB’s coordination guidance and applicable electrical regulations.

The electronic overload function does not replace short-circuit protection.

6. Verify Cabinet Cooling and Mounting

The supplied dimensions are 390 × 186 × 270 mm. Confirm the actual unit dimensions and required installation clearances before designing the motor control cabinet.

Soft starters generate heat during operation, particularly during repeated starts. Cabinet ventilation, ambient temperature, spacing, and duty cycle should be considered during installation.

7. Commissioning and Functional Testing

After installation, inspect power and control wiring, verify grounding, and check all protective devices.

Test the motor’s starting sequence, acceleration behavior, stopping sequence, overload settings, fault indications, and PLC control signals. Record the final parameters for future maintenance.

Compatible System Components

The PST85-600-70 is generally used as part of a complete motor control assembly. The following components may be included depending on the system design.

The listed components are examples of equipment used in a complete motor-control system. They are not necessarily supplied with the PST85-600-70.

Alternative Models and Replacement Considerations

When replacing a PST85-600-70, the new soft starter should be selected according to motor current, operating voltage, connection method, starting duty, and control requirements.

Before choosing a replacement, compare:

• Main circuit voltage.
• Rated motor current.
• In-line and inside-delta ratings.
• Motor power at the actual supply voltage.
• Starting class and duty cycle.
• Current-limit range.
• Starting and stopping ramp functions.
• Control supply voltage.
• PLC and communication requirements.
• Dimensions and cabinet cooling requirements.
• Protection and contactor coordination.

A replacement with the same nominal current may still require changes to wiring, parameters, control logic, or panel layout.

Key Advantages

Reduced Starting Current Impact

The PST85 controls the voltage supplied to the motor during startup, helping reduce the electrical impact associated with direct-on-line starting.

Smoother Mechanical Acceleration

Adjustable starting parameters allow the motor to accelerate progressively, helping reduce sudden torque changes in connected equipment.

Controlled Stopping

The soft starter provides a configurable stopping ramp for applications that benefit from a more gradual stopping sequence.

Integrated Electronic Overload Protection

The built-in electronic overload function supports motor protection when correctly configured for the connected motor.

Adjustable Current Limitation

The current-limit function gives engineers flexibility to adapt starting behavior to the motor and power supply conditions.

Monitoring and Control Interfaces

Relay signals and analog outputs support integration with PLCs and industrial monitoring systems.

Flexible Connection Options

The PST85 supports both in-line and inside-delta connection methods, allowing engineers to select an appropriate arrangement for compatible motor installations.

Technical FAQs

1. What is the ABB PST85-600-70?

The ABB PST85-600-70 is an advanced soft starter designed to control the starting and stopping of three-phase AC motors. Its order number is 1SFA894008R7000.

2. What is the rated operational voltage?

The main circuit operating voltage range is 208–600 V AC. The control supply voltage is 100–250 V AC.

3. What is the rated current of this model?

The rated operational current is 85 A for in-line connection and 147 A for inside-delta connection. The correct rating depends on the installation method.

4. What motor power can the PST85 support?

At 400 V, the published motor power rating is 45 kW for in-line connection and 75 kW for inside-delta connection. At 500 V, the corresponding ratings are 55 kW and 90 kW.

5. Does the PST85 include motor overload protection?

Yes. The device includes electronic overload protection. The motor current setting must be configured according to the connected motor’s nameplate.

6. Can the PST85 connect to a PLC?

Yes. It can be integrated into a PLC-based control system through suitable control signals, relay outputs, analog outputs, and compatible communication accessories.

7. What is the difference between in-line and inside-delta connection?

In-line connection places the soft starter in series with the motor supply conductors. Inside-delta connection places it within a compatible motor delta circuit. The two arrangements have different current ratings and wiring requirements.

8. Can the PST85 be used for pump applications?

Yes. It can be used with compatible pump motors where controlled starting and stopping are required. Pump characteristics and system pressure conditions should be considered when setting the ramps.

9. What should be checked before replacing a PST85-600-70?

Verify the main voltage, motor current, power rating, connection method, starting duty, control supply, wiring, and communication requirements. Also check physical dimensions and protection coordination.

10. Why does the listed weight differ from the catalog value?

The supplied listing weight is 10 kg, while ABB’s catalog gives approximately 11.2 kg for the PST85 rating. Differences may result from measurement methods, product configuration, or whether accessories and packaging are included. Confirm the actual unit weight before shipping.

Procurement and Maintenance Recommendations

When purchasing the ABB PST85-600-70, confirm both the product model and order number: 1SFA894008R7000. This helps distinguish the PST85 from other soft starters with similar current ratings or product descriptions.

For replacement projects, compare the original device’s main-circuit voltage, connection method, motor current, control supply, and starting parameters. Do not select a replacement based only on the motor’s kilowatt rating.

For used or surplus equipment, request clear photographs of the nameplate, terminals, and housing. Check for signs of overheating, damaged terminals, corrosion, or physical impact. Where possible, obtain functional test information and confirm warranty and return conditions.

During maintenance, inspect power connections, control wiring, ventilation paths, and cabinet temperature. Review motor current and starting frequency to determine whether the selected soft starter settings remain appropriate for the operating conditions.

Keep a record of the motor current setting, ramp parameters, current limit, and protection configuration. This information can simplify troubleshooting and reduce commissioning time after equipment replacement.

Conclusion

The ABB PST85-600-70 1SFA894008R7000 Soft Starter is an industrial motor-control device designed for controlled starting and stopping of three-phase AC motors. It supports 208–600 V AC main-circuit operation, 85 A in-line current, and 147 A inside-delta current, with corresponding 400 V motor power ratings of 45 kW and 75 kW.

With adjustable starting and stopping ramps, current limitation, electronic overload protection, and monitoring interfaces, the PST85 can support a range of industrial motor applications. Correct connection selection, parameter configuration, and protection coordination are essential for reliable operation.