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Motor Analysis With A Power Quality Analyzer
- 1. HART Pressure Transmitter Calibration Presenter: Jason Huneycutt Power Quality Applications Engineer Motor Analysis With A Power Quality Analyzer
- 2. motors will fail sooner or later
- 3. test regularly to maximize a motor’s up-time and service life
- 5. Delta Configuration Wye Configuration
- 7. Shorted Windings Can Be Due To Heating Effects That Melt The Insulation Leading To Coil Shorts
- 8. Causes Of Motors Heating Under-Voltage
- 9. Causes Of Motors Heating Over-Voltage
- 10. Over-Loading Causes Of Motors Heating
- 11. Causes Of Motors Heating Unbalance
- 12. Causes Of Motors Heating Harmonics
- 15. 5 1 3Misalignment2 4 Bearing Failures Sealing Poor Mounting Faulty Contamination Lubrication Poor
- 16. 1 Vibration2 Bearing Failures Electric Current Passing Through The Bearing Other Common Causes
- 17. ARCING is caused by the Electric Current passing through the Bearing
- 18. When Current Passes Through The Bearings
- 19. Motor Vibration Causes Mechanical Imbalance Misalignment Faulty Bearings
- 21. Rotor Bar Failure Causes
- 22. -2fm -fm f +fm +2fm 5 5 20 10 10 Sideband Components In The Power Spectrum Of The Stator Current
- 24. Pay Attention To The Power Factor
- 25. Pay Attention To The Power Factor
- 29. Megger’s MPQ1000 Is A Powerful, Simple, Portable Tool For Analyzing Motors.
- 30. Digital Low Resistance Ohmmeter Insulation Resistance Test set 5Kv, 10Kv, 15Kv Hand-held Insulation Tester 1Kv, 2.5Kv
- 31. Megger/Baker AWA Megger/Baker Power Pack With AWA Megger/Baker DX
- 33. Questions or Comments? Email Nicole VanWert-Quinzi nvanwert@Transcat.com Transcat: 800-800-5001 www.Transcat.com For related product information, go to: www.Transcat.com/Megger
Editor's Notes
- Motors will fail, sooner or later.
- In order to maximize a motor’s up-time and service life, the condition of the power driving the motor must be tested regularly.
- This slide shows how to connect your power quality analyzer to motor test specimen. Be sure to know the configuration. The PQ unit will help you determine the quality of power driving your motor. It will also let you know if there are harmonics, transients or other PQevents that may be affecting the life of the motor.
- This slide reflects winding failure due to transients. Transients Can Break Down The Insulation Of The Windings Leading To Shorted Coils. A good power quality will measure transients down to 1 microsecond
- Heating effects will decrease the life of the motor, reduce the viscosity of the bearing grease and the heating effects can cause windings to burn up.
- Motors are constant power devices. As the voltage goes down the current must go up. Heating is a function of 𝐼 2 ×𝑅, so as current rises so does the heat.
- Overvoltage can drive up amperage and temperature even on lightly loaded motors. Inrush current goes up with higher voltage, especially on heavily loaded motors. Efficiency of the motor drops with either high or low voltage.
- In the case of an overloaded motor, individual motor components including bearings, motor windings, and other components may be working fine, but the motor will continue to run hot. The primary symptoms: excessive current draw, insufficient torque overheating.
- Just a 1% unbalance in the phase voltages can lead to a 6 to10% unbalance in phase current. This current unbalance will generate unbalanced heating effects in the coils. This can lead to individual coils burning up and insulation melting leading to shorted coils.
- Harmonics create eddy currents in wires. This eddy current creates magnetic fields that push the current going through the wire to the outside edge of the wire. This is known as skin effect. This increases heating effects in the wire. In addition to skin effect, in a coil wires are adjacent to each other. Adjacent wires create magnetic fields that push the current in the adjacent wire to the outer edge of that wire. This is known as proximity effect. This further increases motor heating effects.
- VFDs Use High Speed Switching IGBTs, which Produce A Great Deal Of High Frequency Voltage Harmonics. A Filter can be Used To Produce A Relatively Clean Drive Current.
- The higher the harmonic order the hotter the motor will get.
- You are probably aware of this but….
- Other bearing failures are….
- Electric Current Passing Through The Bearing causes arcing
- When trouble shooting one of the things to look for is pitting and flutting. As seen in this picture. There shouldn’t be voltage on the shaft but if there is…. The discharge between the bearing and the race causes bearing pitting and the flutting effect. When the motor shaft is turning, the bearing grease is an insulator. It insulates the bearings from the bearing race. This acts as a capacitor. The stator and the rotor generate charge through capacitive coupling. This is electrostatically induced in to the motor shaft. This current then passes through the motor shaft to the bearings. This creates a discharge between the bearing and the race. This discharge causes bearing pitting and the flutting effect. The MPQ1000 will Record both transients and sub-cycle distortions that can cause bearing pitting and fluting as well as insulation breakdown which will lead to shorted coils.
- Negative sequence harmonics are commonly caused by 6 pulse converters, which produce a dominate 5th order negative sequence harmonic. These are present in 3 phase power supplies that are often used in variable frequency drives (VFDs). Negative sequence harmonics have magnetic fields that rotate in the opposite direction of the rotors magnetic field. These harmonics will create counter rotational currents that can lead to vibration. The MPQ1000 will record both voltage and current harmonics and inter-harmonics.
- A rotor bar can be partially or completely cracked. This can occur due to: manufacturing defects frequent starts at rated voltage. thermal stresses vibration
- An Effect Of Broken Bars Is The Appearance Of Sideband Components or inter-harmonics.. These are the frequencies on the immediate left and right sides of the fundamental frequency component. They are usually the reason to side bar damage if caused by harmonics. The MPQ1000 will Perform an FFT (Fast Fourier Transform) analysis to view the current harmonics to identify high side band frequencies, which are a sign of rotor bar damage.
- This is an example of Megger’s MPQ1000 on-board waveform of PF.
- This slide is an example of a demand report the high powered software the unit comes with generates with just one click of the mouse. A low power factor can cause motors to be unable to obtain full power. This can be caused by long cable runs that are not a sufficient gauge. The MPQ1000 will record all power parameters as well as Power Factor.
- This slide reflects two charts a good PQ analyzer can create. An on line motor analysis and start up current in rush test. The MPQ1000 allows you to perform both. A good analyzer will record all parameters on a cycle by cycle basis. With the MPQ1000 when the motor starts up it will capture over 600 cycles of inrush current on all channels.
- In Addition The MPQ1000 Can Be Connected To A Network For Remote Analysis. This allows you to remotely view results. Start and stop recording, view real time data, change the analyzer configuration, transfer data remotely or automatically have the data transferred periodically. Ideal for long evaluations.
- The MPQ1000 comes with everything you see here, plus the free high powered software that makes analyzing motors easy.
- Other useful tools Megger has to offer for testing motors are the DLRO series or digital low resistance ohmmeter for doing bar to bar tests on DC motor rotors. And MIT series Insulation testers to check the insulation resistance from phase to phase and the phases to the frame or earth.
- With Megger’s acquisition of Baker, we now also offer these units that can do Baker’s famous surge test. Transcat does carry these now as well, so feel free to request a quote if necessary.