Product Overview

The ABB PST50-600-70 1SFA894005R7000 Soft Starter is an electronic motor-starting device designed to control the acceleration and stopping of three-phase AC motors. It belongs to ABB’s PST advanced soft starter range and is intended for industrial applications where controlled motor starting, reduced mechanical stress, and dependable motor protection are important.

When a conventional motor starter switches a motor directly onto the power supply, the motor can draw a high starting current and produce sudden mechanical torque. These effects may place additional stress on electrical distribution systems, gearboxes, couplings, belts, pumps, and other connected equipment. A soft starter reduces these effects by gradually controlling the voltage applied to the motor during startup.

The PST50-600-70 supports main-circuit operating voltages from 208 to 600 V AC and has a rated operational current of 50 A for in-line connection. At 400 V, its rated motor power is 25 kW for in-line connection and up to 45 kW for inside-delta connection, subject to the applicable installation and selection requirements.

The unit uses a control supply of 100–250 V AC at 50/60 Hz. Its control circuit also supports 24 V DC operation. The PST advanced range provides adjustable starting and stopping parameters, electronic overload protection, current-limit functionality, and monitoring signals that can be integrated into an industrial control system.

The PST50-600-70 is suitable for motor-driven equipment such as pumps, fans, compressors, conveyors, and general industrial machinery when the motor ratings and starting conditions are within the device’s specified limits.

Technical Specifications

Note: Electrical ratings depend on the connection method, operating conditions, and application requirements. Always confirm the motor nameplate current and the manufacturer’s selection instructions before installation.

Function and Working Principle

The ABB PST50-600-70 controls motor starting and stopping by regulating the voltage applied to the motor. Unlike a direct-on-line starter, which applies the supply voltage immediately, the soft starter increases the motor voltage according to a configured starting ramp.

This controlled voltage adjustment helps limit starting current and reduces the sudden torque changes associated with direct starting.

1. Controlled Motor Acceleration

During startup, the PST50-600-70 gradually increases the voltage supplied to the motor. The motor accelerates according to the selected ramp time and initial voltage settings.

This function is useful for machines that experience mechanical stress during sudden acceleration. Pumps, conveyors, and compressors can benefit from a more controlled starting sequence when the soft starter is correctly sized and configured.

2. Adjustable Starting Parameters

The soft starter allows engineers to adjust starting parameters according to motor and load requirements. These settings can include initial voltage, ramp time, current limit, and motor rated current.

Correct configuration is important because different loads require different starting torque. A pump may need a different starting profile from a loaded conveyor or compressor.

The objective is to achieve reliable acceleration without unnecessarily increasing current or extending the starting period.

3. Controlled Motor Stopping

The PST50-600-70 also supports controlled stopping through an adjustable stopping ramp. Rather than removing the motor supply abruptly, the soft starter can gradually reduce the applied voltage.

This can be useful in fluid-handling systems where sudden pump stopping may contribute to pressure changes or water hammer. The actual stopping effect depends on the pump, piping system, fluid conditions, and selected settings.

A soft stop should not be confused with a mechanical braking system. It controls the electrical supply during stopping but does not provide the same function as a dedicated motor brake or regenerative drive.

4. Current-Limit Function

The current-limit function allows the starting current to be restricted according to the application. The PST50-600-70 supports an adjustable current-limit range of 1.5–7 times the rated operational current.

This can help reduce the impact of motor starting on the electrical supply. However, an excessively low current limit may prevent a heavily loaded motor from accelerating correctly.

The current limit should therefore be selected with reference to the motor’s starting torque requirements and the driven equipment’s mechanical load.

5. Electronic Motor Overload Protection

The PST advanced range includes electronic overload protection. The motor current setting must be configured to match the connected motor and its operating conditions.

This protection helps identify overload conditions and supports equipment protection. It does not replace all required upstream short-circuit protection, isolation devices, or safety systems.

Role in Industrial Control Systems

The ABB PST50-600-70 can serve as the motor-starting component in an industrial control panel. It works alongside PLCs, contactors, circuit protection devices, sensors, and operator interfaces to coordinate motor operation.

PLC Integration

A PLC can control the soft starter through suitable control signals and monitor its available status outputs. Typical commands include start and stop requests, while feedback signals can indicate operating status, faults, or protection conditions.

The exact interface depends on the system wiring and the soft starter’s configured signal connections. Engineers should consult the relevant terminal diagrams when designing the control circuit.

HMI and Operator Monitoring

An HMI can display motor status, alarms, and process information through the PLC or another supported control arrangement.

Operators may use the HMI to initiate a motor-start sequence, stop equipment, or view fault information. Access permissions and safety interlocks should be incorporated into the overall control design.

Motor Protection Coordination

The PST50-600-70’s electronic overload protection should be coordinated with upstream circuit breakers, fuses, contactors, and other protective equipment.

The selected protective devices must meet the installation’s short-circuit rating and applicable electrical standards. Correct coordination helps protect the motor starter, motor, and connected wiring.

Industrial Process Coordination

In a production system, the soft starter can be incorporated into a wider sequence controlled by a PLC. For example, a PLC may permit a pump to start only after valves are in the correct position or allow a conveyor to operate after upstream equipment has completed its startup sequence.

This coordination helps prevent unintended machine operation and supports consistent production processes.

Industrial Applications

The PST50-600-70 is designed for industrial motor-starting applications where controlled acceleration and stopping are required. Its 50 A in-line rating and application-specific motor power ratings make it suitable for appropriately sized three-phase motors.

1. Pumping Systems

Pumps are widely used in water treatment, industrial circulation, cooling systems, and fluid transfer processes.

A soft starter can reduce the sudden electrical and mechanical effects associated with motor startup. Its controlled stopping function may also help reduce abrupt pressure changes in suitable pump installations.

The actual benefit depends on pump characteristics, piping design, valve arrangement, and the selected ramp settings.

2. Industrial Fans

Large ventilation and air-handling systems often use three-phase motors to drive fans. Direct starting can create a sudden mechanical load and a high current demand.

The PST50-600-70 can provide a controlled starting process for compatible fan motors. Engineers should consider fan inertia, starting torque, motor cooling, and the number of starts per hour when selecting the device.

3. Air Compressors

Industrial compressors may require controlled motor starting to reduce the impact of startup on electrical and mechanical systems.

The soft starter can be used with compatible compressor motors when the compressor’s unloading arrangement and starting torque requirements are properly considered.

The compressor manufacturer’s requirements should determine the appropriate starting sequence and operating conditions.

4. Conveyor Systems

Conveyors are used in manufacturing, packaging, warehousing, and material-handling operations. Sudden motor acceleration can cause belt movement, product displacement, or mechanical stress.

A soft starter can help provide smoother acceleration for compatible conveyor motors. For applications requiring continuous variable-speed control, however, a variable frequency drive may be more appropriate.

5. General Industrial Machinery

The PST50-600-70 can be applied to other motor-driven equipment where its current, voltage, starting capacity, and duty ratings are suitable.

Before selecting the soft starter, engineers should assess the motor’s rated current, load inertia, required starting torque, operating frequency, and expected number of starts per hour.

Installation and System Integration

Correct installation is essential for safe operation and reliable motor starting. The PST50-600-70 should be installed by qualified personnel in accordance with the manufacturer’s instructions and applicable electrical regulations.

1. Verify Main Circuit Voltage

Confirm that the incoming supply is within the soft starter’s rated operational voltage range of 208–600 V AC.

The main circuit frequency is 50/60 Hz. The supply voltage, motor voltage, and wiring arrangement must be compatible with the selected application.

2. Select the Correct Connection Method

The PST50-600-70 supports in-line and inside-delta connection arrangements.

For in-line connection, the rated operational current is 50 A. The inside-delta arrangement has a different current and motor-power rating, so the correct connection diagram and selection data must be followed.

Do not use the higher inside-delta motor power rating as the in-line rating. Incorrect wiring or rating selection can result in equipment damage or unsafe operation.

3. Check Control Supply

The rated control supply voltage is 100–250 V AC at 50/60 Hz. The control circuit also supports 24 V DC operation.

Verify the control supply terminals and wiring requirements before connecting the device. The main circuit and control circuit should be wired according to the manufacturer’s diagrams.

4. Configure Motor Parameters

Enter the correct motor rated current and configure the starting and stopping parameters.

Important settings include:

• Motor rated current.
• Initial starting voltage.
• Starting ramp time.
• Stopping ramp time.
• Current limit.
• Overload protection parameters.
• Application-specific control settings.

The settings should be tested under the actual operating load rather than selected solely from generic values.

5. Provide Suitable Cabinet Ventilation

The supplied dimensions are 260 × 160 × 196 mm, and the product weight is 4.8 kg.

Allow sufficient space for mounting, cable access, heat dissipation, and maintenance. The enclosure should be suitable for the installation environment and provide the ventilation required by the manufacturer’s instructions.

6. Test the Starting and Stopping Sequence

After wiring and configuration, test the motor under controlled conditions.

Verify the direction of rotation, starting current, acceleration time, stopping behavior, overload protection, and PLC or operator commands. Confirm that the motor accelerates reliably under the expected load.

Document the final parameter settings for future maintenance and replacement work.

Compatible System Components

The PST50-600-70 is normally installed as part of a complete motor-control system. The following components may be used depending on the application design.

The final component selection depends on the system’s electrical design and the applicable protection requirements. These items are not necessarily supplied with the soft starter.

Alternative Models and Replacement Considerations

When replacing an existing PST50-600-70, the replacement should be selected according to motor current, voltage, duty, control supply, and connection method.

These models are not automatic substitutes. Before selecting a replacement, compare:

• Rated operational voltage.
• Rated current for the intended connection method.
• Motor power at the actual supply voltage.
• Control supply voltage and frequency.
• Starting and stopping requirements.
• Overload and current-limit functions.
• Control signal and communication requirements.
• Mounting dimensions and cabinet ventilation.
• Required protection and contactor coordination.

A replacement with a higher current rating may still require wiring, protection, or parameter changes. Always check the manufacturer’s documentation before approving a substitute.

Key Advantages

Controlled Motor Starting

The soft starter gradually increases motor voltage during startup, helping reduce the abrupt current and torque effects associated with direct-on-line starting.

Adjustable Starting and Stopping

Configurable ramp settings allow engineers to adapt motor acceleration and stopping behavior to the driven equipment.

Integrated Electronic Overload Protection

Electronic overload protection supports motor protection when the rated motor current and operating parameters are correctly configured.

Current-Limit Function

The adjustable current-limit function provides additional control over the motor’s starting current, subject to the torque requirements of the application.

Flexible Connection Options

The PST50-600-70 supports both in-line and inside-delta arrangements, allowing different installation designs when correctly selected and wired.

Industrial Control Integration

The device can be incorporated into PLC-based motor-control panels using suitable control signals and status feedback.

Broad Motor Application Range

The soft starter can be used with compatible pumps, fans, compressors, conveyors, and other industrial motor-driven systems.

Technical FAQs

1. What is the ABB PST50-600-70?

The ABB PST50-600-70 is an electronic soft starter designed to control the starting and stopping of three-phase AC motors. Its product number is 1SFA894005R7000.

2. What is the rated current of this soft starter?

Its rated operational current is 50 A for in-line connection. The inside-delta connection has a different current rating and must be selected according to the manufacturer’s documentation.

3. What is the maximum operating voltage?

The rated operational voltage range is 208–600 V AC for the main circuit.

4. What control supply voltage does it require?

The rated control supply voltage is 100–250 V AC at 50/60 Hz. The control circuit also supports 24 V DC operation.

5. What motor power can the PST50-600-70 handle?

At 400 V, the rated motor power is 25 kW for in-line connection and up to 45 kW for inside-delta connection. The actual selection must follow the applicable motor current and installation requirements.

6. Does the PST50-600-70 include overload protection?

Yes. The PST advanced range includes electronic motor overload protection. The motor rated current must be correctly configured.

7. Can this soft starter be used with a PLC?

Yes. It can be incorporated into a PLC-based motor-control system through suitable control and status connections. The exact interface depends on the wiring design and application.

8. Is the PST50-600-70 suitable for pumps?

It can be used with compatible pump motors. Controlled starting and stopping may help reduce abrupt mechanical and hydraulic effects, depending on the pump and piping system.

9. What is the difference between a soft starter and a variable frequency drive?

A soft starter primarily controls motor voltage during starting and stopping. A variable frequency drive adjusts output frequency and voltage to provide continuous motor-speed control. If an application requires regular speed adjustment during operation, a variable frequency drive may be more suitable.

10. What should be checked before purchasing a replacement?

Verify the complete product number, rated current, main-circuit voltage, control supply, connection method, dimensions, and physical condition. Also check whether the replacement meets the original motor’s starting and overload requirements.

Procurement and Maintenance Recommendations

When purchasing the ABB PST50-600-70 1SFA894005R7000, verify the complete product number and confirm that the unit matches the electrical requirements of the intended application.

For new, surplus, or refurbished equipment, request clear photographs of the product label, terminals, and external housing. Confirm the condition of the power terminals, control connections, and mounting points. For critical applications, request appropriate functional testing and confirm the applicable warranty and return conditions.

During routine maintenance, inspect the soft starter for dust accumulation, loose connections, discoloration, signs of overheating, and damage to the housing or terminals. Maintain suitable cabinet ventilation and follow the manufacturer’s maintenance recommendations.

The motor’s rated current and protection parameters should be reviewed whenever the connected motor or mechanical load changes. Any adjustment to the starting ramp, stopping ramp, or current limit should be tested under actual operating conditions.

For replacement projects, record the original wiring arrangement and parameter settings before removing the installed unit. Verify the new device’s connection method and protection coordination before energizing the system.

Conclusion

The ABB PST50-600-70 1SFA894005R7000 Soft Starter is an industrial motor-starting device designed for three-phase AC motors operating within a main-circuit voltage range of 208–600 V AC. It provides a 50 A in-line current rating, adjustable starting and stopping parameters, current-limit functionality, and integrated electronic overload protection.

With its support for in-line and inside-delta connections, the PST50-600-70 can be used in a range of industrial motor-control applications when correctly selected and installed. Accurate verification of the motor rating, control supply, connection method, and protection settings is essential for reliable operation.