The factory testing technology for three-phase induction motors is a critical process to ensure their performance, safety, and reliability, encompassing multidimensional tests such as electrical characteristics, mechanical properties, and environmental adaptability. The following provides a comprehensive overview of test items, technical methods, system features, and data analysis:
1. Insulation Performance Testing
• Insulation Resistance Measurement: A megohmmeter is used to measure the insulation resistance between windings and the housing, as well as between phases. For motors below 500V, the resistance should not be less than 0.5MΩ (or 5MΩ for fully rewound windings). The instrument range is selected based on voltage level.
• Withstand Voltage Test: An AC or DC voltage higher than the rated voltage (e.g., 2× rated voltage + 1000V) is applied for 1 minute to verify insulation strength. For example, motors below 500V undergo an AC withstand voltage test using a 2500V megohmmeter.
2. DC Resistance Measurement
• Measured in a cold state using a double-arm bridge or micro-ohmmeter. The deviation in resistance among the three phases should not exceed 5% of the average value. Abnormal readings may indicate short circuits, open circuits, or wiring errors.
3. No-Load Test
• The motor runs without load while no-load current and losses are measured. The no-load current should be balanced across phases, with a deviation ≤10%. Excessive current may result from insufficient turns, uneven air gaps, or core quality issues.
4. Locked-Rotor Test
• The rotor is immobilized, and a low voltage is applied to measure locked-rotor current and losses, verifying starting performance. Abnormal current may indicate broken rotor bars or substandard aluminum resistivity.
5. Inter-Turn Insulation Test
• The motor runs at 130% of rated voltage for 5 minutes under no-load conditions to detect inter-turn short-circuit risks.
6. Temperature Rise Test
• The motor operates under rated load until thermal stability is achieved. Winding and bearing temperatures are monitored to ensure they do not exceed insulation class limits (e.g., ≤130°C for Class B).
1. Automation & Intelligence
• Distributed test systems (e.g., YMT-G series) integrate voltage regulators, PLCs, and industrial control software, supporting multi-station parallel testing with a daily capacity exceeding 1,000 units.
• Built-in standard databases enable automatic pass/fail determination and generate test reports with characteristic curves.
2. High Precision & Reliability
• Utilizes 0.2-class precision transformers, 32-bit ARM processors, and high-resolution AD converters for data accuracy.
• Safety mechanisms include fault alarms, manual/auto switching, and multi-layer protection during withstand voltage tests.
3. Data Management & Traceability
• Test data is automatically stored by serial number, supporting queries by model, date, etc. Statistical analysis of pass rates and trend monitoring aids production optimization.
Resistance Anomalies: Phase imbalance may indicate winding shorts or missed wire connections; overall high resistance may result from excessive turns or thin wire diameter.
No-Load Current Anomalies: Excessively high current may stem from insufficient turns, excessive air gaps, or incorrect power frequency; abnormally low current may arise from wiring errors (e.g., star connection mistaken for delta).
Locked-Rotor Current Anomalies: Excessively high current may indicate rotor resistance design flaws or excessive aluminum purity; low current may suggest broken rotor bars or improper assembly.
Test Power Supply: Voltage waveform distortion ≤5% (≤2.5% for temperature rise tests); frequency deviation ±1%.
Instrument Accuracy: Electrical meters ≥0.5-class, transformers 0.2-class, thermometers ±1°C error.
Current technology enables automated testing for high-voltage motors (up to 10kV) and integrates remote maintenance and AI diagnostics. Future advancements in IoT will drive real-time monitoring and predictive maintenance.
