Motor Current Signature Analysis

Motor Current Signature Analysis for condition monitoring of Electrical Rotating Machines, MCSA Basics, Faults That Can Be Detected With MCSA,

1. Motor Current Signature Analysis By Ankit Singh Basera 1

2. Lecture 3.1 Introduction 2

3. Introduction Electrical Signature Analysis (ESA) concept originates from early 1970s and was first proposed for use in nuclear power plants for inaccessible motors and motors placed in hazardous areas E SA is useful for analysing not only electrical induction motors, but also generators , power transformers as well as other electric equipment. Most popular of these techniques are : Current Signature Analysis (CSA), Voltage Signature Analysis (VSA), Extended Park’s Vector Approach (EPVA) and Instantaneous Power Signature Analysis (IPSA ) 3

4. MOTOR CURRENT SIGNATURE ANALYSIS BASICS Reference: Stator Current Monitoring System 4

5. MOTOR CURRENT SIGNATURE ANALYSIS BASICS Motor stator windings are used as transducer in MCSA 5

6. Fault Detection Techniques Used in MCSA FAST FOURIER TRANSFORM INSTANTANEOUS POWER FFT WAVELET ANALYSIS PARK’S VECTOR APPROACH ARTIFICIAL INTELLIGENCE 6

7. Faults That Can Be Detected With MCSA BROKEN ROTOR BARS They can cause sparking and overheating in a motor. When broken rotor bars are present, current components in stator windings can be detected at frequencies given by: Broken Rotor Bar Frequency Supply Frequency Pole Pairs Slip K=1,2,3……….. 7

8. If difference between main and sideband component is: Greater than 50 dB then Rotor has No Fault Between 40 dB and 50 dB then Rotor has One Broken Bar Less than 40 dB then Rotor has Many Broken Bars and Broken End Rings 8

9. Reference: Frequency Spectrum From Motor With Broken Rotor Bars 9

10. Faults That Can Be Detected With MCSA 2 ) AIR-GAP ECCENTRICITY Air-gap eccentricity represents a condition when air gap distance between the rotor and the stator is not uniform. . In case of static eccentricity sideband components appear at frequencies determined by : Eccentricity Frequency Supply Frequency Pole Pairs Slip No of Rotor Bars +1, -1 1,3,5,7………………. 10

11. Air Gap – Static Eccentricity Air Gap- Dynamic Eccentricity 11

12. Faults That Can Be Detected With MCSA 3) BEARINGS DAMAGE Bearing faults are due to misalignment of bearing, excessive load on shaft, less lubrication, fatigue, etc. 12

13. Sideband frequency components due to bearing damage 13

14. Faults That Can Be Detected With MCSA 4) SHORTED TURNS IN STATOR WINDINGS Shorted turns produce excessive heat in stator coil and current imbalance Motor current components that are influenced only by shorted turns can be detected at frequencies and described by Shorted Turn Frequency Supply Frequency Pole Pairs Slip 1,3,5,7……………….   14