A Novel Algorithm to Detect Broken Bars in Induction Motors

Abstract

A new algorithm is proposed in order to detect and quantify partially broken bars in induction motors during start-up without load. In the qualification process, no threshold is used. It uses the principle of the harmonic generated by the broken bar in the stator current, it should vary with the slip to confirm the failure and provide more security in the diagnosis. A severity index is also proposed, based on the maximum peaks of the Teager energy operator of the Gaussian filter applied in the stator current signal. Experimental data were used to validate the algorithm, comparing rotors manufactured with one partially bar, one failed bar, and two completely failed bars, arranged in a variety of ways. The results show that the algorithm qualifies correctly the faulty bar, even for a partially broken bar. In the quantification phase, the severity index of the fault shows the higher sensibility in comparison to the state-of-the-art. Its value for a 3 HP motor is: 8.837 × 10−10 for a healthy rotor, 2.553 × 10−8 for a partially broken bar, and 4.058 × 10−7 for one broken bar.

Keywords

• broken bar
• induction motor
• current signature analysis
• start-up
• Gaussian bandpass filter
• Teager energy operator