ABB PSTX/PSR Soft Starter Field Troubleshooting and Maintenance Guide

2.2 Trip or protection action during startup process

Common causes and solutions for malfunction indicator lights

Overload protection (PSE/PSTX yellow LED flashing): The motor experiences prolonged overcurrent or excessive load inertia, resulting in a starting time exceeding the set level (class 10/20/30). 1. Confirm that the motor nameplate current is consistent with the soft starter parameter settings.

2. Extend the start-up ramp time or switch to torque control.

3. Check if the mechanical load is stuck (bearings, belts).

Underload protection (for water pumps): The pump is running dry, the coupling is broken, and the belt slips, causing a sudden decrease in load. 1. Check the inlet pressure and flow rate of the pump.

2. Adjust the underload protection threshold (PSE/PSTX can set the action percentage).

The rotor of the locked rotor protection motor is stuck, and the current cannot decrease after starting. 1. Immediately cut off the power and manually turn the wheel to check the mechanical jamming point.

2. If it is a conveyor, check if the materials are piled up.

Phase sequence protection (PSTX) incoming line phase sequence error, compressor and other equipment are prohibited from reversing. Swap the two incoming lines arbitrarily, or modify the "Allow reverse start" option in the parameters.

Motor thermal imager/PT100 protection winding temperature is too high, usually accompanied by poor ventilation or frequent start stop. 1. Check the cooling fan.

2. Reduce the number of startups per hour (PSR ≤ 100 times/hour, large PSTX ≤ 10 times/hour).

On site reminder: PSTX provides detailed fault records (event logs), and current, voltage, temperature, and other data from the last 30 faults can be viewed through the keyboard or Softstarter Care software, greatly improving diagnostic efficiency.

2.3 Excessive starting current or failure to limit current

The core value of a soft starter is to reduce the starting current of the motor. If you observe that the peak starting current is still close to the DOL (direct start) level, please investigate:

Initial voltage set too high

If the initial voltage potentiometer of PSR is adjusted to above 80%, the starting current will approach straight up. It should be reduced to 30%... 50% for testing.

The current limit amplitude is too high than the rated current of the motor

The current limiting function in PSE/PSTX can be set to 200%... 500%. For light load start-up (such as no-load fans), setting 300% may still generate high current; It can be reduced to 250% and combined with longer slope time.

The load requires a larger starting torque

For high inertia loads such as centrifugal fans and ball mills, voltage ramp starting may fail. In this case, torque control (PSE/PSTX) or dual current limit (PSTX's Dual Current Limit) should be used instead. First, a higher current pulse should be used to overcome static friction, and then the acceleration should be reduced to a lower current for smooth acceleration.

Bypass relay adhesion

In rare cases, the built-in bypass contact does not disconnect during shutdown, resulting in the next startup being equivalent to DOL. Measure the resistance of the main circuit after power failure (normally, there should be thyristor impedance between the output and input terminals of the soft starter).

2.4 Severe water hammer phenomenon (pump application)

The water hammer when the pump stops is the main cause of pipeline damage. PSE and PSTX are equipped with a torque stop function to eliminate water hammer.

Fault phenomenon: When the pump is stopped, the pipeline vibrates violently, and the pressure gauge pointer instantly falls back and rebounds.

Solution:

Confirm that the stop mode is set to "Torque Stop" instead of "Coast to stop" or "Voltage ramp stop".

Adjusting the stopping time of the slope: Usually 2-5 seconds can effectively suppress water hammer, but too long a time may lead to backflow.

Check if the "Torque Control" icon in the PSE display is illuminated. If none, it means the parameter is not activated.

Extension function: PSTX also has a "pump cleaning" function - by briefly reversing the flow direction to flush the impeller and pipeline, it prevents blockage. If the flow rate of the pump decreases after long-term operation, you can try manually executing this function.

2.5 Vortex Compressor Specific Issues (PSRC)

The vortex compressor requires a start-up time of less than 1 second to ensure the formation of a lubricating oil film. PSRC has fixed factory parameters (initial voltage 50%, startup ramp 0.5 seconds) that cannot be modified, which is its advantage.

Common misconception: When users use regular PSR instead of PSRC, the startup time can exceed 2-3 seconds, resulting in abnormal noise or even jamming of the compressor.

Troubleshooting:

Confirm that the soft starter model is PSRC-600-70 instead of PSR-600-70.

If it still cannot be started, check if the initial voltage of 50% is sufficient to overcome the back pressure of the compressor. Some large-sized compressors may require an increase in initial voltage, but PSRC does not support adjustment - in this case, it should be replaced with PSTX and a customized short ramp should be used.