LTI ServoOne Servo Troubleshooting Guide

LTI ServoOne Servo Troubleshooting Guide

In the field of modern high-end equipment manufacturing and precision motion control, the ServoOne series servo drives launched by LTI DRiVES (now part of Danaher Group) have become the preferred choice for industries such as packaging, printing, machine tools, and robots due to their excellent overload capacity, modular hardware architecture, and extremely high safety integration. This series covers a wide power range from 2A to 450A and is divided into ServoOne Junior (compact single axis), ServoOne single axis system (standard type), and ServoOne multi axis system that supports energy feedback.

For on-site engineers in the "search for solutions" phase, it is crucial to quickly locate the fault point and perform EMC compliant replacement operations when the equipment is facing safety circuit false triggering, DC bus overvoltage, encoder communication interruption, or emergency replacement of spare parts. This article will provide you with a detailed practical troubleshooting manual from four dimensions: safety function (STO), multi axis system maintenance, encoder interface debugging, and hardware replacement.

Deep analysis and troubleshooting of STO safety functions

One of the core highlights of the ServoOne series is its integrated security features. Both the standard STO (Safe Torque Off) and the optional Integrated Safety Control comply with EN ISO 13849-1 PL e and EN 61508 SIL3 standards.

On site debugging and diagnosis of STO function

The STO function prevents the motor from generating torque by cutting off the drive signal of the power stage without disconnecting the main power supply.

Interface check: For ServoOne single axis/multi axis systems, safety signals are usually connected to X8 terminals (ASI+/ASI -). When conducting on-site inspections, first use a multimeter to measure whether there is a 24V DC voltage between the terminals. If the voltage is lost, the driver will report a safety stop fault.

Safety loop closed-loop: The safety status of STO is usually output to the upper safety PLC through ASO1/ASO2 feedback contacts or Ready signal. If the upper computer reports "safety circuit not closed", it is necessary to check whether the feedback contact of X8 interface is stuck due to internal relay failure, or whether the external safety door switch is disconnected.

Integrated Safety Control (SafePLC S): For models equipped with integrated safety control (such as up to SO84.072), an independent safety program runs inside the drive. If a malfunction occurs, the SafePLC S software on the PC side needs to be used to connect to the Ethernet port of the driver and read the diagnostic logs of the safety controller. Common issues include cross short circuits in safety input channels (requiring dual channel redundancy) or loose Safe Cross Communication (SCC) network cables (SCC-04), which result in the inability to synchronize safety status between multiple axes.

2. Taboos for troubleshooting

Before conducting any safety circuit inspection, it is necessary to ensure that the motor has stopped rotating. Do not short-circuit the safety input signal for forced operation, as this will cause the device to lose its PL e level security protection, which is a serious violation of regulations.

Maintenance of Multi Axis Systems and Regenerative Power Supply (PSU)

The ServoOne multi axis system consists of a DC powered axis controller and a power supply unit (PSU) with a sine wave regenerative power supply. This design not only shares the DC bus, but also feeds back the braking energy to the grid, which is energy-saving and environmentally friendly.

1. DC bus overvoltage and undervoltage faults

Overvoltage: When a motor in a multi axis system suddenly stops or the load is lowered due to gravity, energy is fed back to the DC bus. If the feedback energy exceeds the absorption capacity of the power supply unit, the bus voltage will rise and trigger an overvoltage alarm. When troubleshooting, first check whether the incoming voltage of the power supply unit (such as SO84.040. S, etc.) is normal. Secondly, check if external braking resistors are configured in the system (if regenerative power mode is not used). For renewable power sources, it is necessary to ensure that the Mains synchronization signal of the power supply unit is normal, otherwise energy cannot be fed back.

Undervoltage: If the DC bus voltage drops, it is necessary to check whether the input main contactor of the power supply unit is engaged and whether the internal pre charging circuit is normal. Use an oscilloscope to observe the waveform of the DC bus. If there are severe fluctuations, it may be due to an internal short circuit in one of the inverters in the multi axis system or aging of the bus capacitor (such as the BG7 model 7200 μ F capacitor).

2. Maintenance of liquid cooling system

High power modules (such as BG3 and above) support liquid cooling. If the on-site report shows a "overheating" fault of the radiator, in addition to checking the coolant flow and temperature, it is also necessary to check whether there is leakage in the quick connector of the liquid cooling connection kit (LCS01). The coolant temperature should be controlled below 40 ° C and should not be lower than the ambient temperature by more than 10 ° C, otherwise it may cause a short circuit of condensed water.