1. Problem Description and Impact Size
This guide is intended for detection and correction of errors in servo motor drives related to loss of position and encoder deviation. Problems may occur in various types of industrial equipment, including conveyor systems, screw pumps, presses and machining tools. The severity ranges from "minor" to "critical", depending on the impact on production capacity and safety.
2. Safety
Requirements for carrying out the work:
- Use personal protective equipment (gloves, safety goggles, protective jacket)
- Perform the lockout/tagout (LOTO) procedure before disconnecting the power supply
- Detect and remove energy storage in electric drives
- Do not perform work in the presence of electrical or mechanical working tensions
3. Required Tools
| Tool | Model | Measurement range | Objective |
|---|---|---|---|
| Multimeter | Fluke 289 | 0-1000 V, 0-200 A | Voltage, current, resistance measurements |
| Vibration Analyzer | Brüel & Kjær 4390 | 0-20,000 Hz | Definition of vibration characteristics |
| Thermocamera | FLIR T1020 | -20°C to 600°C | Detection of component overheating |
| Encoder sensor | Encoder test unit | 0-10,000 ppm | Sensor Function Check |
4. First inspection and control
| Requirement | Action |
|---|---|
| Operating Conditions | Record temperature, humidity, pressure, vibrations |
| Latest changes | Check for availability of component replacements or settings |
| History of Alarms | Record error codes and time of occurrence |
| Physical condition | Check for mechanical damage |
5. Systematic Diagnostic Flow
- Symptom: Loss of position
- Check the sensor coding range
- Measure vibration at the drive output
- If vibration is higher than 4.5 mm/s, check the mechanical connection
- If vibration is higher than 10 mm/s, check the electronics exception
- Symptom: Encoder sensor deviation
- Check the input terminal voltage
- Measure the current within the range of 0.5-1.5 A
- If current is higher than 2.0 A, check the electronics exception
- If the current is lower than 0.3 A, check the encoding sensor
- Symptom: Unstable drive operation
- Measure the temperature on the drive surface
- If the temperature is higher than 65°C, check the cooling
- If temperature is higher than 80°C, check the electronics
6. Error Cause Matrix
| Symptom | Likely Causes | Diagnostic test | Expected result |
|---|---|---|---|
| Loss of position | Insufficient sensor contact | Resistance check at the input connector | Impedance 100-500 Ohm |
| Loss of position | Mechanical disconnection | Vibration measurement | Higher 4.5 mm/s |
| Sensor deviation | Incorrect parameter settings | Drive parameter check | The parameters do not conform to the specification |
| Sensor deviation | Unbalanced loading | Vibration measurement | Higher than 10 mm/s |
| Unstable operation | Drive Overheating | Temperature Measurement | Higher than 65°C |
| Unstable operation | Electric Exception | Voltage Measurement | Voltage below 220 V |
7. Analysis of Main Causes
7.1 Loss of Position
Loss of position may be caused by insufficient sensor contact, mechanical disconnection, or incorrect drive settings. Insufficient contact may occur due to cable damage or contamination of contact surfaces. Mechanical disconnection may occur due to screw damage or vibrational changes. Incorrect parameter settings may lead to incorrect drive operation.
7.2 Sensor Deviation
Sensor position deviation may be caused by incorrect parameter settings or unbalanced loading. Incorrect parameters may lead to incorrect position detection. Unbalanced loading may lead to vibrational deviations, which affect the coding accuracy.
7.3 Unstable operation
Unstable operation may be caused by overheating of the drive or an electrical fault. Overheating may occur due to insufficient cooling or incorrect parameter settings. An electrical fault may occur due to unstable power supply or internal defect.
8. Step-by-step correction procedure
8.1 Loss of Position
- Check the encoder sensor cable and restore the contact
- Measure the resistance at the sensor input connection
- If the resistance is below 100 Ohm, perform contact cleaning
- Measure vibration at the drive output
- If vibration is higher than 4.5 mm/s, check the mechanical connection
- Set the drive parameters according to the specification
- Check the restoration of the position after adjustment
8.2 Sensor Deviation
- Check the drive parameters and set them in accordance with the specification
- Measure vibration at the drive output
- If vibration is higher than 10 mm/s, check the load
- Measure the voltage at the input connector
- If the voltage is lower than 220 V, perform the electrical supply adjustment
- Check the encoder sensor restoration after setup
8.3 Unstable operation
- Measure the temperature on the drive surface
- If the temperature is higher than 65°C, check the cooling system
- If the temperature is higher than 80°C, perform drive adjustment
- Measure the voltage at the input connector
- If the voltage is lower than 220 V, perform the electrical supply adjustment
- Check the stability of operation after correction
9. Preventive Measures
| Main cause | Preventive maintenance | Control Method | Recommended interval |
|---|---|---|---|
| Insufficient sensor contact | Cleaning of contacts and connections | Resistance Measurement | Monthly |
| Mechanical disconnection | Checking and Tightening Screws | Vibration measurement | Monthly |
| Incorrect parameter settings | Periodic adjustment of the drive | Measurement of parameters | Quarterly |
| Unbalanced load | Load Measurement | Vibration measurement | Monthly |
| Drive Overheating | Periodic cooling | Temperature Measurement | Monthly |
| Electric Exception | Periodic power supply adjustment | Voltage Measurement | Monthly |
10. Production Components and Spare Parts
| Component description | Specification | When to replace | Category UNITEC-D |
|---|---|---|---|
| Encoder sensor | 0-10,000 ppm | After losing position | C-1220 |
| Sensor cable | 0.3 mm², 250 V | After losing position | C-1225 |
| Mechanical fastener screw | M8, 4.8 | After losing position | C-1230 |
| Multimeter | 0-1000 V, 0-200 A | After losing position | C-1240 |
| Vibration Analyzer | 0-20,000 Hz | After losing position | C-1250 |
| Thermocamera | -20°C to 600°C | After losing position | C-1260 |
Visit our e-catalog: https://www.unitecd.com/e-catalog/
11. References
- ISO 13849-1: Industrial Safety of Automated Systems
- EN 60204-1: Safety of electrical equipment for industrial applications
- DSTU 3121-2011: Requirements for Electrical Equipment
- OEM rare diagnostic manuals
- Technical Service Manuals UNITEC-D
Conclusion
This guide provides technical support for detecting and correcting errors in servo motor drives related to loss of position and encoder deviation. Performing diagnostic actions using specified tools and measurements allows effectively identifying the cause of the error and correcting it.
