Because Motors Fail
Not all winding faults start as ground faults. Instead, they can start as a weakness in the winding insulation system that may eventually fault to ground when the motor stops running.
Motor testing is integral to the success and efficiency of your business. ALL-TEST Pro instruments ensure that testing your motor is safe, easy, and dependable. Our capabilities for troubleshooting and predictive maintenance are a means of sustaining critical systems and achieving meaningful ROI. Don’t leave motor failure up to chance – reap the cost-saving benefits of complete motor testing.
Winding Faults & ALL-TEST Pro Instruments
Winding defects begin as energy crossing an insulation fault, which isolates at least one turn. There are 4 basic types of winding faults:
- Between 2 or more conductors in a coil
- Between coils in the phase
- Between coils in different phases
- Between a coil or phase and ground
Symptoms of winding faults include higher operating temperatures, nuisance tripping, and reduced motor life. The short-term result of these faults is reduced efficiency, and higher operating costs. The long-term result is always motor failure.
What is MCA?
Motor Circuit Analysis (MCA™) is a de-energized test method to assess the health of the motor. This method can be initiated from the Motor Control Center (MCC) or directly at the motor. The advantage to testing from the MCC is that the entire electrical portion of the motor system, including the connections and cables between the test point and the motor, is evaluated.
How does it work?
The electrical portion of the a 3 phase motor system is made up of the basic motor circuit, which is nothing more than 3 simple RCL circuits (resistive, capacitive, inductive). Each basic circuit represents one phase of the three-phase motor system. Since each phase of the motor system is identical, each basic circuit should respond the same way to an applied signal. This is also true for single-phase and DC motors.
ALL-TEST Pro instruments apply a series of low voltage, non-destructive sinusoidal AC signals through the motor windings and measure the response to these signals. Winding faults are indicated by variances in the response to the applied signal through the windings. This de-energized test takes only a few minutes and can even be performed by an entry-level technician.
The measurements* rendered by MCA™ include:
- Resistance for connection and cable related issues.
- Impedance and inductance for rotor issues, such as air gap, casting voids, and broken/fractured rotor bars.
- Dissipation Factor to determine if the winding to ground is contaminated or overheated.
- Developing winding shorts, turn to turn, coil to coil, or phase to phase are detected and trended using Fi (phase angle) & I/F (current frequency response) measurements.**
- TVS™ (Test Value Static) is compared to a Reference TVS™ and if a change occurs this indicates that a change in the condition of the stator and/or rotor has occurred.
- Dynamic Stator and Rotor Signatures*** is used to automatically assess the condition of the stator and rotor, and provides the Stator & Rotor ‘OK’, ‘Warn’, or ‘Bad’.
- It is important to note that TVS™ is independent of rotor position in a motor in good condition. TVS™ and the Dynamic Stator and Rotor Signatures are patent and patent-pending and represent a significant breakthrough in motor testing technology. Insulation to ground is also tested looking for issues related to the ground wall.
*Number of measurements depend upon model of MCA instrument.
**Fi is the phase angle of the applied voltage and the resulting flow of current measured in degrees. I/F is the percent reduction in current flow when the applied frequency is exactly doubled.
***Dynamic Stator and Rotor Signature is for testing AC induction with squirrel-cage rotor motors <1000V.
Why Traditional Megohmmeter Testing Isn’t Enough?
Avoid unplanned downtime by proactively and thoroughly testing your motor for faults. This means going beyond the capabilities of a traditional Megohmmeter. Megohmmeter insulation testing will only detect faults to ground. Since only a portion of motor electrical winding failures begin as ground faults, they will go undetected using this method alone. Moreover, surge testing requires the application of high voltages. This can be destructive when testing a motor, making it an unsuitable method for troubleshooting and true predictive maintenance testing.
ALL-TEST Pro offers more complete motor testing than any other options on the market. Our instruments go above and beyond normal testing equipment for accurate, safe, and fast motor testing. Motor testing using an MCA™ tool is very easy to implement, and the test takes less than 3 minutes. Save money and time by proactively detecting developing faults before they cause irreversible motor failures.
What is ESA?
Electrical Signature Analysis (ESA) is an energized test method where voltage and current waveforms are captured while the motor system is running, to assess the health of the motor system. Energized testing provides valuable information for AC induction and DC motors, generators, wound rotor motors, synchronous motors, machine tool motors, and more.
How does it work?
All ESA systems require motor nameplate information of voltage, running speed, full load current, and horsepower (or kW). Optional information including rotor bar and stator slot count, bearing numbers, and information for driven load components – such as blade count for a pump or tooth count for a gearbox application – can be entered for a more detailed and accurate analysis.
A Fast Fourier Transform (FFT) creates the spectral display, and the algorithms perform a spectral analysis on voltage and current waveforms to detect faults related to incoming power, the control circuit, the motor itself, or the driven load. These can then be trended for condition-based maintenance and predictive maintenance purposes.
The key difference between Motor Current Signature Analysis (MCSA) and ESA is with MCSA the FFT is done on the current waveform only, not the voltage. This makes it more difficult to easily distinguish incoming power related problems from motor and driven load problems. With ESA you have both the current and the voltage FFT on the same screen, so it’s just a matter of comparing the voltage and current FFT spectra to determine the source of the fault.
Why is it important?
Finding a motor fault before it breaks can save your organization countless hours of downtime and thousands of dollars in savings, justifying itself immediately. Our ESA tester is actually 2 instruments in 1 – a complete Power Quality Analyzer (PQ) and complete Motor Analyzer (ESA). When in PQ mode it can be used for energy data logging, harmonic analysis, voltage and current charting, viewing waveforms, waveform capture of sags and swells, transient capture, and event capture.
ALL-TEST Pro offers unmatched motor testing technology. Our instruments are portable, safe, and easy-to-use – allowing you to evaluate equipment in the field, shop floor, or at a service facility. Save yourself hours that might be spent on troubleshooting – or, better yet, save yourself catastrophic damage and costs due to motor failure. Learn more about our full line of ALL-TEST Pro products.