PSTX370-600-70 370 A 208-600 V AC Softstarter

When a 200 kW motor on a 400 V AC supply starts direct-on-line, the resulting inrush current can stress upstream protection and mechanical couplings. The ABB PSTX370-600-70 addresses this by providing a rated operational current of 370 A and a voltage span of 208 ... 600 V AC, with three-phase control through voltage or torque ramps. This softstarter integrates a built-in bypass, reducing panel space and energy losses during run.

Key Features and Electrical Specifications

The PSTX370-600-70 is engineered for exact motor starting. Its control supply voltage accepts 100 ... 250 V AC at 50/60 Hz, while the control circuit operates at 24 V DC. The built-in bypass carries the load after start, and relay outputs provide RUN, TOR, and Event signals in normally open state.

• Rated operational current: 370 A inline, 640 A inside delta.
• Rated operational voltage: 208 ... 600 V AC.
• Control supply voltage: 100 ... 250 V AC, 50/60 Hz.
• Control circuit voltage: 24 V DC.
• Starting capacity: 4xIe for 10s.
• Analog outputs: 0…10 V, 0…20 mA, 4…20 mA.
• Communication: Modbus RTU built-in; optional ANYBUS modules for Profinet, Profibus, Modbus TCP, Ethernet IP.
• Degree of protection: IP00 at main terminals.

Failure Mode Analysis: Preventing Motor Start Issues

Common failure modes in motor starting include locked rotor, phase reversal, and undervoltage. This unit includes locked rotor protection, phase reversal protection, and voltage sags detection. Additionally, the built-in electronic overload protection with time-to-cool prevents thermal damage. For pump applications, pump cleaning and motor heating functions reduce jamming and condensation risks. The limp mode maintains two-phase control if one thyristor set is shorted, allowing continued operation until maintenance.

Integration and Communication

The softstarter offers four communication paths: hardwired Start/Stop/Reset, three programmable digital inputs, built-in Modbus RTU, and optional ANYBUS modules for major fieldbuses. Integration note: wiring into fieldbus networks may require an external gateway or connection module; confirm cables and gateways with AutoDCSTech. The detachable full graphic display carries IP66 and 4x outdoor rating, enabling local configuration and diagnostics.

Installation and Commissioning

Mount This unit with attention to the main circuit bar terminals, which require a tightening torque of 25 N·m. The hole diameter for main connections is 8.5 mm. Control circuit wiring accepts rigid conductors up to 2.5 mm². The ambient operating temperature range is -25 ... +60 °C, supporting demanding environments. The built-in bypass simplifies wiring by eliminating external contactors.

Applications and Use Cases

Typical applications include pumps, fans, compressors, and conveyors. In a water treatment plant, the softstarter ramps a 200 kW pump over 120 seconds, reducing water hammer. For a conveyor system, torque control ensures smooth acceleration of loaded belts. The sequence start function coordinates multiple motors, while emergency/fire pump mode ensures reliable operation during critical events.