Introduction

The ABB PST44-600-70 1SFA894004R7000 Soft Starter is an advanced motor-starting device designed to control the acceleration and stopping of three-phase AC motors. It belongs to ABB’s PST series and is intended for industrial applications where controlled motor starting, reduced mechanical stress, and adjustable operating parameters are important.

When a large motor starts directly across the line, it can draw a high inrush current and produce sudden mechanical torque. These effects may place additional stress on electrical distribution systems, motors, couplings, belts, pumps, and other connected equipment. A soft starter helps manage this process by gradually controlling the voltage applied to the motor during startup.

The PST44-600-70 supports a main-circuit operating voltage range of 208–600 V AC and has a rated operational current of 44 A for in-line connection. At 400 V, its in-line motor power rating is 22 kW. It also supports Inside Delta installation, with a rated operational current of 76 A and a corresponding 400 V motor power rating of 37 kW.

The unit operates with a control supply voltage of 100–250 V AC at 50/60 Hz. It includes electronic motor overload protection, adjustable starting and stopping parameters, current-limit functionality, and programmable monitoring and control functions.

The PST44-600-70 is suitable for appropriately rated pumps, fans, compressors, conveyors, and other industrial motor-driven equipment. Correct selection depends on motor current, starting conditions, connection method, operating frequency, and application duty.

Technical Specifications

Note: Current and motor-power ratings depend on the connection method and operating conditions. Always use the appropriate ABB selection data for the intended application.

Product Overview

The ABB PST44-600-70 is designed to provide controlled starting and stopping for industrial three-phase motors. Unlike a conventional direct-on-line starter, which applies the supply voltage immediately, a soft starter gradually increases the motor voltage according to configured starting parameters.

This controlled voltage ramp can reduce electrical and mechanical stresses during motor startup. It is particularly useful in applications where sudden torque changes may cause vibration, pressure fluctuations, belt movement, or unnecessary wear on mechanical components.

The PST series is an advanced soft-starter range with adjustable motor-control parameters and integrated protection functions. The PST44-600-70 supports both in-line and Inside Delta motor connections, allowing engineers to select an appropriate installation arrangement according to the motor and system design.

Its 44 A in-line rating and 76 A Inside Delta rating should not be interpreted as interchangeable operating values. The selected connection method determines which rating and corresponding motor power data apply.

The unit is designed for integration into industrial motor-control panels. It can operate alongside circuit breakers, contactors, overload protection arrangements, PLCs, and other control equipment as part of a complete motor-control system.

Function and Working Principle

1. Controlled Motor Starting

When a motor starts directly across the line, it may draw several times its normal operating current. The resulting electrical demand can affect the power supply and other equipment connected to the same distribution system.

The PST44-600-70 gradually increases the voltage supplied to the motor during startup. This allows the motor to accelerate more progressively instead of receiving the full supply voltage immediately.

The starting ramp can be adjusted to suit the motor and mechanical load. A suitable ramp helps balance acceleration time, starting current, and the torque required by the application.

2. Soft Stopping

The soft starter can also control motor stopping by gradually reducing the applied voltage over a configured period.

This function is useful in applications where abrupt stopping may create mechanical or process disturbances. For example, controlled stopping of a pump can help reduce sudden changes in fluid flow.

The actual stopping behavior depends on the load characteristics and system configuration. A soft stop is not a substitute for a mechanical brake or a safety-rated stopping function where those are required.

3. Current Limit Function

The current-limit function allows engineers to set a starting-current restriction according to the motor and electrical supply requirements.

This can help manage the current drawn during acceleration, particularly in installations where the available supply capacity is limited or several motors operate simultaneously.

The current limit must be configured carefully. If it is set too low, the motor may not develop sufficient torque to accelerate the connected load within the required time.

4. Electronic Motor Overload Protection

The PST44-600-70 includes electronic overload protection. This function helps protect the motor against sustained overload conditions when the device is configured correctly for the connected motor.

The motor’s rated current and applicable protection parameters should be entered according to its nameplate and the installation requirements.

Electronic overload protection does not replace all upstream short-circuit protection or the safety devices required by the machine design.

5. In-Line and Inside Delta Operation

The PST44-600-70 supports two installation methods: in-line and Inside Delta.

In an in-line arrangement, the soft starter is connected in series with the motor supply conductors. The rated operational current for this model is 44 A.

In an Inside Delta arrangement, the soft starter is connected within the motor’s delta winding circuit. This arrangement provides a different current relationship, and the published rating for this model is 76 A.

Inside Delta installation requires a motor with an appropriate six-terminal winding arrangement and a correctly designed circuit. Engineers must follow ABB’s connection diagrams and verify motor compatibility before commissioning.

Applications

1. Industrial Pump Systems

Pumps are widely used in water treatment, industrial circulation, chemical processing, and fluid-transfer systems. Direct-on-line starting can create sudden changes in motor torque and fluid pressure.

The PST44-600-70 can provide controlled acceleration and stopping for compatible pump motors. Adjustable starting and stopping parameters can help reduce mechanical shock and support more stable operation.

For pump applications, engineers should consider the pump’s load characteristics, required acceleration time, pressure behavior, and any need for a separate water-hammer control strategy.

2. Industrial Fans and Blowers

Fans and blowers are commonly used in ventilation systems, dust collection equipment, industrial cooling, and air-handling installations.

A soft starter can help reduce the mechanical shock associated with starting large rotating assemblies. Controlled acceleration may also reduce sudden belt tension changes and stress on fan bearings and couplings.

The motor’s starting torque and the fan’s inertia must be considered when selecting the ramp settings.

3. Air Compressors

Industrial air compressors often operate under demanding starting conditions. Their starting behavior depends on compressor type, pressure conditions, unloading arrangements, and the mechanical load.

The PST44-600-70 can be used in a compatible compressor installation to manage motor acceleration. The compressor’s unloading system and starting sequence must be coordinated with the soft starter settings.

4. Conveyor Systems

Conveyors are used in manufacturing, packaging, warehousing, and material-handling operations. Abrupt motor starting can cause sudden movement of belts, rollers, and transported materials.

The soft starter can help provide smoother motor acceleration and reduce mechanical stress in suitable conveyor applications.

For heavily loaded conveyors, engineers should confirm that the selected starting current and ramp settings provide sufficient torque to move the load.

5. Industrial Processing Machinery

Mixers, agitators, and other process machines may require controlled motor starting to reduce mechanical shock during acceleration.

The PST44-600-70 can be considered for compatible motor applications where its voltage and current ratings meet the process requirements.

The equipment’s load profile, starting frequency, and required acceleration time should be evaluated before selecting the soft starter.

Advantages and Key Features

Controlled Acceleration

The adjustable starting ramp helps the motor accelerate progressively. This can reduce sudden mechanical loading on connected equipment.

Reduced Starting Current

The soft-start function can limit the high current demand associated with direct-on-line motor starting. The actual starting current depends on the motor, load, current-limit settings, and supply conditions.

Soft-Stop Capability

Controlled stopping can help reduce abrupt mechanical or process changes in suitable applications, especially in pump and fluid-handling systems.

Integrated Electronic Overload Protection

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

Adjustable Current Limit

The current-limit function gives engineers an additional way to manage motor starting behavior and adapt the starter to the available electrical supply.

Flexible Connection Methods

Support for both in-line and Inside Delta arrangements provides flexibility in motor-control panel design. The correct arrangement must be selected according to the motor winding configuration and ABB’s wiring instructions.

Industrial Motor-Control Integration

The PST44-600-70 can be incorporated into a larger motor-control system with contactors, protective devices, PLCs, and operator interfaces.

Installation and System Integration

1. Verify the Motor and Supply Ratings

Before installation, confirm the motor’s rated voltage, current, power, frequency, and connection arrangement.

The PST44-600-70 supports a main-circuit voltage range of 208–600 V AC. The motor’s actual operating voltage must fall within the permitted range.

Do not select the soft starter based on kilowatt rating alone. Motor current, starting torque, load inertia, starting frequency, and duty classification must also be considered.

2. Select the Correct Connection Method

Determine whether the installation will use an in-line or Inside Delta arrangement.

For in-line installation, use the 44 A rating and corresponding motor power data. For Inside Delta installation, use the 76 A rating and verify that the motor has the required winding terminals and connection configuration.

Incorrect wiring can damage the starter or motor. Use the manufacturer’s connection diagrams and have the installation completed by qualified personnel.

3. Install in a Suitable Control Cabinet

Mount the soft starter in an appropriately designed electrical enclosure. Provide the ventilation and spacing required by the manufacturer’s installation instructions.

The cabinet should protect the device from unsuitable environmental conditions such as excessive dust, moisture, and corrosive substances.

The supplied dimensions are 260 × 160 × 196 mm. Confirm the actual mounting drawing and required clearance before finalizing the panel layout.

4. Connect the Control Supply

The control supply voltage is 100–250 V AC at 50/60 Hz. Verify the actual control supply before energizing the unit.

Control wiring should be arranged to reduce interference from high-current motor conductors. Follow the terminal identification and wiring requirements in the installation documentation.

5. Configure Starting and Stopping Parameters

Set the motor rated current, starting ramp, stopping ramp, current limit, and applicable protection settings.

The settings should reflect the connected motor and mechanical load. A ramp that is too short may produce abrupt acceleration, while a ramp that is too long may cause unnecessary motor heating.

6. Test the Complete Motor-Control Circuit

After installation, check power connections, control wiring, grounding, protective devices, and motor connections.

Perform controlled commissioning tests to verify the starting sequence, stopping behavior, current response, motor direction, and protection functions.

Record the final parameter settings for future maintenance and troubleshooting.

Compatible System Components

These components are examples of equipment used in a complete motor-control installation. They are not necessarily included with the PST44-600-70.

Technical FAQs

1. What is the ABB PST44-600-70?

The ABB PST44-600-70 is an advanced soft starter designed to control the starting and stopping of three-phase AC motors. It belongs to the ABB PST series and supports both in-line and Inside Delta installation methods.

2. What is the order number of this soft starter?

The ABB order number is 1SFA894004R7000. This number should be checked against the product label when purchasing a replacement.

3. What is its rated operational current?

The rated operational current is 44 A for in-line connection and 76 A for Inside Delta connection. The applicable rating depends on the installation method.

4. What is the main-circuit voltage range?

The main-circuit operating voltage range is 208–600 V AC. Confirm the motor and supply ratings before installation.

5. What control supply voltage does it require?

The control supply voltage range is 100–250 V AC at 50/60 Hz.

6. What motor power can it support at 400 V?

For in-line connection, the published 400 V motor power rating is 22 kW. For Inside Delta connection, the corresponding rating is 37 kW. The selected connection method and application duty must be considered.

7. Does the PST44-600-70 have overload protection?

Yes. It includes electronic motor overload protection. The motor’s rated current and protection parameters must be configured correctly.

8. Can it be used with a PLC?

It can be incorporated into a PLC-based motor-control system. The actual interface and control method depend on the system design and the available communication or control options.

9. What is the difference between in-line and Inside Delta installation?

In-line installation connects the soft starter in series with the motor supply conductors. Inside Delta installation places the starter within the motor’s delta winding circuit. The two methods have different current ratings and wiring requirements.

10. What are the dimensions and weight?

The supplied dimensions are 260 × 160 × 196 mm, and the listed weight is 4.8 kg. These values are consistent with the product information for this model. Confirm the physical unit and packaging configuration when calculating shipping requirements.

Procurement and Maintenance Recommendations

When purchasing the ABB PST44-600-70, verify both the model designation and order number. The identification should read PST44-600-70 and 1SFA894004R7000.

For replacement applications, compare the original unit’s voltage range, rated current, connection method, control supply, and protection requirements. A soft starter with a similar current rating may not be suitable if its connection method or motor power rating differs.

For used or surplus equipment, inspect the enclosure, terminals, display, connectors, and visible electronic components. Request clear photographs of the nameplate and available test information. Confirm the product’s condition and any included accessories before purchase.

During maintenance, keep the cabinet clean and maintain the required ventilation. Inspect electrical connections for signs of overheating, looseness, or corrosion. Review the motor’s operating current and starting behavior when investigating repeated overload or starting faults.

Parameter settings should be documented after commissioning. This helps maintenance personnel restore the intended operating configuration following equipment replacement or troubleshooting.

Conclusion

The ABB PST44-600-70 1SFA894004R7000 Soft Starter is an advanced motor-control device designed for three-phase AC applications requiring controlled acceleration and stopping. With a 208–600 V AC main-circuit voltage range, 44 A in-line rating, and 76 A Inside Delta rating, it can support appropriately selected industrial motors.

Its adjustable starting and stopping functions, current-limit capability, and integrated electronic overload protection make it suitable for a range of pump, fan, compressor, conveyor, and process-machinery applications.

Correct selection and installation require careful attention to motor current, connection method, control supply, starting duty, and electrical protection. Verifying these details helps ensure that the soft starter is properly matched to the motor and the overall industrial control system.