Electric motors are the workhorses of modern industry, powering pumps, compressors, conveyors and machine tools. When the motor fails, operations come to a halt, and the cost of an unplanned shutdown goes far beyond the price of the motor itself. It is estimated that the main causes of motor failures are 51% from bearing‐related issues, 16% winding and insulation breakdowns, 5% rotor faults, and the remainder comes from external factors such as misalignment or unbalanced loads.
Most of these failures develop slowly over time, which means they can be detected with condition monitoring tools long before audible noises or heat show up.
Predictive maintenance technologies can help service and teams, like at OTC Industrial Technologies, act early to prevent the three costliest failure modes: fluting-related bearing damage, lubrication-related bearing damage, and rotor/winding faults.
Have a motor failure that continuously slows you down? Turn to OTC for electrical and industrial motor repair expertise.
Electrical motor fluting is a form of electrical bearing damage that can quietly shorten motor life long before a failure becomes obvious. It occurs when stray electrical currents pass through the motor shaft and bearings instead of following a controlled path to ground.
In today’s facilities, where variable-frequency drives (VFDs) are widely used to improve efficiency and control, this risk has increased significantly. Left unaddressed, fluting accelerates bearing wear, drives up vibration levels, and can lead to premature motor failure and unplanned downtime.
Electric motor fluting appears as a washboard-like pattern of microscopic ridges on the bearing race. High-frequency voltage pulses generated by VFDs can build up between the motor shaft and frame. When that voltage discharges through the bearing, it creates tiny arcs that melt and pit the race surface. Over time, those pits align into the ridged pattern that defines fluting. Because the damage starts at a microscopic level, motors often continue running until audible noise or vibration appears, by which point the bearing race is already severely compromised. As VFD adoption continues to grow, fluting has become one of the most common and costly electrical motor failure modes OTC’s electrical and motor repair teams see in the field.
Once ridges form, the bearing no longer runs smoothly. The noise and vibration quickly worsen, heat builds, and the machine must be shut down to replace the bearings. In process industries, an unexpected shutdown can cost tens or hundreds of thousands of dollars per hour. Fluting also tends to recur if the underlying electrical discharge is not addressed, leading to repeated failures and reputational damage.
Traditional vibration monitoring detects a fluted bearing only after the ridges have formed and noise is audible, which may be weeks or days before catastrophic failure. More proactive methods include:
The most effective solution is to prevent shaft currents from passing through the bearing. Options include installing insulated bearings, using grounding brushes or conductive rings to shunt current to ground, and fitting proper filters or reactors to VFD outputs. Ensuring that drives and motors are correctly sized and grounded also reduces common‑mode voltages.
Don’t settle for disruptions. Contact OTC to get ahead of potential bearing failures.
Proper lubrication is one of the most important and most misunderstood factors in electric motor health. Bearings rely on the correct type, amount, and application of lubricant to reduce friction, manage heat, and protect internal surfaces from wear. When lubrication practices are inconsistent or based on habit rather than specification, bearing life drops dramatically, making lubrication-related damage one of the leading causes of premature motor failure in industrial environments.
Studies show that up to 80% of bearing failures are related to lubrication issues, such as using the wrong grease, insufficient lubrication, or, more commonly, over-greasing. While it may seem harmless, over-greasing a sealed bearing can significantly impair heat rejection, increase churning losses, and overload or damage the seals. Under-lubrication allows metal-to-metal contact, leading to micro-pitting and fatigue. By the time a bearing is hot to the touch or audibly noisy, the damage is typically already advanced.
A single bearing replacement might cost only a few hundred dollars, but the real expense comes from unscheduled downtime. An asset that earns $20,000 per hour can rack up $160,000 in lost production during an eight‑hour bearing replacement, excluding secondary losses. If improper lubrication also affects multiple machines, the cumulative impact on throughput and labor quickly multiplies.
Implementing a lubrication program based on ultrasound feedback ensures bearings receive the right amount of grease at the right time. Selecting lubricants with appropriate viscosity and additive packages for the application, using automatic lubricators with controlled delivery, and training technicians to avoid “pump until it squirts out” practices are essential. When ultrasonic tools indicate impending failure, the bearing can be replaced proactively during a planned outage.
The experts at OTC can create or implement a lubrication program specific to your needs. Contact us today to get started.
While bearing failures are more common, rotor and stator winding faults are often the most costly and disruptive motor failures. These components are central to how an electric motor produces torque and converts electrical energy into mechanical power. When rotor bars or stator windings are compromised, damage tends to propagate quickly, often leaving little opportunity for corrective action before the motor must be taken out of service.
Although less common than bearing issues, rotor and stator faults are among the most expensive failures because they often require complete motor replacement. A broken rotor bar increases the current in adjacent bars, causing a cascade that leads to multiple broken bars where the rotor may overheat, crack and seize. Stator winding failures typically begin as insulation degradation. Thermal aging, over‑voltage, or contamination degrade insulation over years or decades. Once insulation punctures, arcing and shorted turns quickly destroy the winding.
Rotor bar failures cause torque pulsations and overheating. When several bars break, the motor loses torque and must be taken out of service immediately. The cost includes not only the motor (often tens of thousands of dollars) but also the downtime and potential secondary damage to driven equipment. Winding failures may necessitate rewinding or replacing the motor and can take weeks to repair, disrupting production schedules.
Prevent rotor and winding failures by maintaining proper line voltage, ensuring motors are not overloaded, and specifying high‑quality insulation systems. When ESA or partial‑discharge monitoring indicates a developing fault, plan a rewind or motor replacement during a scheduled outage. For wound motors, cleaning and re‑varnishing insulation at regular intervals extends life.
For fast, reliable solutions, contact the experts at OTC today to keep your facility moving.
Motor failures follow a predictable P‑F curve: the period between the Potential failure (P) and the Functional failure (F). Early detection technologies sense subtle changes long before a machine emits audible noise.
As illustrated below, ultrasonic analysis detects lubrication issues when friction first increases; vibration analysis picks up mechanical defects slightly later; thermography reveals heating closer to functional failure; and audible noise is a final warning just before catastrophic failure. Deploying tools at each stage maximizes warning time so maintenance can be scheduled rather than forced by breakdown.
Need a partner who can help keep your motors online and reduce downtime? Contact OTC for your service and repair needs.
Large rotating machinery fails for many reasons, but three patterns are responsible for much of the unplanned downtime and cost: electrical fluting, improper lubrication and rotor/winding faults. These failures develop silently over weeks or years, but the experts at OTC know how to combat and prevent these failures. Combining predictive technologies within a structured maintenance program, OTC can help your plants detect the potential failure, plan repairs during convenient outages and avoid the enormous costs associated with reactive maintenance.
Get started today and eliminate the potential for downtime.
Article written by Marvin Joiner – General Manager OTC Spartanburg