Who failed who? | Predictive motor maintenance

Imagine this. Every hour, you take $10,000 out of your wallet, drop it on the ground, and walk away. Sign me up, right? Well, in the pulp and paper industry, the cost of downtime for a paper machine is about $10,000 per hour. Multiply that by 18 hours and you are looking at a very hefty loss for a rather preventable issue – motor failure.  

Motors are everywhere, especially in the paper industry, with some plants having thousands of motors in one facility. At this magnitude, the probability of motor failure is high, particularly with the destructive “run-to-fail” mentality that many companies adopt. If motor testing is only performed on an as needed basis, unplanned downtime is widespread. Whereas, a healthy, reliable motor can drive an organization’s revenue, profit, and efficiency.

Here is where our good friend, predictive motor maintenance, jumps in. A great predictive maintenance program will reduce unscheduled downtime, predict impending failures, and identify potential problem areas before they create expensive costs for you and your company. After diagnosing issues and taking corrective action, the life of your motor (and its insulation) will be extended. Need a visual? See below.

Today, we are going to look at the two major categories of electric motor testing: static and dynamic.

Static motor testing

In a static motor test, operators are capable of simulating “real world” situations when motors are off-line, which provides insight into the integrity and condition of a motor’s insulation and circuit. This allows electricians, engineers, and technicians to predict or identify imminent equipment failures before inducing unplanned downtime.

Effective Static Test Equipment will test a motor at voltage levels that mimic those the motor will experience in its normal daily operations without destructive currents.

One of the most prevalent and valuable tests is the surge test, which ensures the integrity of a motor’s turn-to-turn insulation. Many motor winding insulation fiascos begin as turn-to-turn failures, which ultimately damage the strength of the ground wall insulation, leading to a catastrophic motor failure. With surge testing, motor disasters are avoided by detecting problems in their earliest stage, replacing or repairing parts, and avoiding unplanned downtime altogether. During a surge test, a fast, high-voltage impulse is applied to a winding, producing a voltage difference between adjacent wire loops. If there is turn-to-turn insulation damage, the voltage difference between the two wires will show up as a patter change on the surge waveform test.

Many static motor analyzers will generate trend logs and reports, indicating potential decline or degradation and giving valuable insight into a motor’s health.

Dynamic motor testing

A dynamic motor analyzer is a multifaceted tool, locating and identifying power-related, load, vibration, and circuit condition problems, while the motor is in-service. Dynamic testing can differentiate between mechanical and electric issues, as well as provide detailed diagnostics for all three components of a motor – power source, load source, and the motor itself. This differentiation allows maintenance professionals to make more precise decisions concerning repairs or replacement, which can elongate the service life of a motor.

When a dynamic test is performed, the motor is powered on and performing in its daily environment. Data collection is safe, fast, and nonintrusive, and it should be performed more frequently than static testing. Compared to static testing, this is a relatively new, but rapidly emerging, monitoring approach.

The testing capabilities of a dynamic monitoring system are extensive. We’ve outlined the top features right here. Dynamic motor analyzers can…

• Calculate speed and torque, define rotor bar issues, and measure distortion
• Identify mechanical issues, including bearing problems or motor shaft misalignment
• Provide information regarding power quality, voltage condition, unbalances, and distortion

Which is better?

Well, static testing is the most effective way to measure the integrity of your motor’s insulation, while dynamic testing provides critical insight into your motor’s power condition, load, life, and operation. Together, they are a powerful duo – giving you a comprehensive illustration of your motor’s health and providing a foundation for a successful predictive maintenance program.