Based on real industrial fault cases of PUTAI motor, this article shares a practical and accurate judgment method for motor turn-to-turn faults, which is widely applicable to medium and high voltage motors, AC motors and brushed DC motors in industrial operation and test scenarios.
1. Overview of Motor Turn-to-Turn Faults
The winding of all conventional industrial motors, including AC motors and brushed DC motors, is composed of multiple turns of enameled wire wound continuously. When the inter-turn insulation layer ages, wears or fails, short circuits will occur between overlapping coil turns of the same winding. This turn-to-turn short circuit will directly disable part of the winding coils and make them lose working efficacy.
Once a turn-to-turn fault occurs in medium and high voltage motors and other industrial PUTAI motor products, the internal winding magnetic field will present an asymmetric distribution state. Meanwhile, the current of the remaining normal winding coils will rise abnormally. In actual operation, the faulty motor will show typical abnormal characteristics including increased vibration, elevated operating current and reduced output power.
Whether in trial operation or formal service of industrial motors, turn-to-turn faults have obvious recognizable symptoms. The most direct manifestations include unbalanced three-phase current, peculiar burnt insulation odor, dull and stuffy operating noise, and significantly intensified motor vibration. In severe cases, the faulty AC motors and brushed DC motors will even produce smoke and flashover discharge, causing serious equipment operation failures.
In the disassembly and fault diagnosis process of faulty medium and high voltage motors, technicians often encounter difficulties in distinguishing turn-to-turn faults, phase-to-phase faults and earth faults due to similar surface damage characteristics. Focusing on practical on-site identification skills, this article mainly elaborates on the accurate screening and judgment method for turn-to-turn faults of PUTAI motor series products.
The attached picture shows the on-site shooting of a faulty motor rotor in a real fault analysis project. Judging from the surface damage traces, many on-site technicians initially had divergent judgments, with some suspecting a turn-to-turn fault and others judging it as a phase-to-phase fault. After comprehensive professional detection and verification, the core cause of the fault was finally confirmed as phase-to-phase fault, which is the primary failure factor of the motor equipment.
2. In-depth Analysis of Motor Winding Fault Causes
For winding fault diagnosis of PUTAI motor (covering medium and high voltage motors, AC motors and brushed DC motors), we adopt a two-step comprehensive analysis method based on the fault location and damage spread range.
First, locate the fault position accurately. The fault point of the above faulty motor is exactly at the phase-to-phase insulation interval of the winding, which is a typical prerequisite for phase-to-phase faults and provides a basic basis for preliminary fault classification.
Second, penetrate the surface phenomenon to identify the essential fault type, which is the core skill to distinguish turn-to-turn faults from phase-to-phase faults. The key judgment standard is to check the corresponding opposite end of the winding fault point. For standard turn-to-turn faults of industrial motors, obvious slight burn marks will appear on the opposite side of the fault winding due to current conduction and insulation breakdown.
In the actual detection of this faulty equipment, no abnormal burn marks were found on the opposite end of the winding fault point, and the damage fault was completely limited to a single end of the winding. This feature fully conforms to the typical failure characteristic of motor phase-to-phase faults, eliminating the possibility of turn-to-turn faults.
Subsequent articles will combine more on-site fault cases of PUTAI medium and high voltage motors, AC motors and brushed DC motors to conduct targeted in-depth analysis on the triggering mechanisms and preventive measures of motor phase-to-phase faults.
