Industrial AC Motors Guide

Industrial electric motors are machines that convert energy into motion. The majority of electric motors rely on the interaction between electrical current in a wire winding and the motor’s magnetic field to generate torque that’s applied to the motor’s shaft. AC motors deliver a high speed-to-torque ratio and perform reliably in even the most demanding environments.

Renown Electric carries a large inventory of AC motors suitable for industrial applications, and we offer a range of maintenance, management, shop services, and field services for industrial AC motors.

How an Industrial AC Motor Works

AC motors are a type of electric motor that is powered by an alternating current (AC). AC motors are typically comprised of two basic components: a rotor and a stator. The stator is the outer, stationary part of the motor. It features coils that are supplied with alternating current to produce a rotating magnetic field. The rotor is the inner part of the motor. It produces a second rotating magnetic field and is attached to the output shaft.

While AC motors come in several variations, industrial applications mainly rely on three-phase AC motors. Three-phase motors produce constant current, at a much greater output than single-phase motors. Industrial AC motors are designed to handle more demanding work and meet the needs of heavy-duty equipment. AC motors range from fractional horsepower to over 100,000 horsepower.

There are several types of AC electric motors, including:

1.Synchronous motors: These motors run at a constant speed and have a rotor that turns at the same speed as the rotating magnetic field in the stator. They are often used in applications where precise speed control is necessary, such as in ball mills, mixers, clocks, timers, and robotics.

2.Induction motors: These are the most commonly used type of AC motor. They have a simple design and are reliable and efficient. They work by using a rotating magnetic field in the stator to induce a current in the rotor, which then creates its own magnetic field and causes the rotor to turn. There are two main types of induction motors:

i. Single-phase motors: These motors feature one main winding and one auxiliary winding. They are used when there is a single-phase supply, and they are smaller and less expensive than other types of AC motors.

ii. Three-phase motors: A type of polyphase motor, three-phase motors deliver greater output than single-phase systems but operate in a similar manner. The stator poles in three-phase motors are unaligned with each other, causing the rotor to pass by the stator poles at different times.

3.Brushless DC motors: These are actually AC motors that are powered by a DC source, and they are becoming increasingly popular in a variety of applications, including electric vehicles and drones. They do not have brushes, which makes them more reliable and efficient than traditional DC motors.

4.Stepper motors: These are motors that move in small, precise steps and are often used in applications where precise positioning is necessary, such as in 3D printers and CNC machines. They work by using a magnetic field to attract the rotor to different positions.

5.Linear motors: These are motors that move in a straight line rather than rotating. They are often used in applications where high-speed, precise movement is necessary, such as in industrial automation and robotics. They work by using a series of magnets to create a magnetic field that pushes the rotor along a linear path.

The majority of AC motors for industrial applications are three-phase AC induction motors, due to their low cost and reliability.

Since AC motors deliver continuous energy changes, they are ideal for demanding applications like those seen in industrial environments. While DC motors are preferred for hand tools or large high-torque applications like steel mill rolling equipment and paper machines, AC motors are commonly used in equipment such as:

• Compressor power drives
• Air conditioning compressors
• Hydraulic pumps
• Irrigation pumps
• Conveyor systems
• Shredders
• Die casting machines
• Sheet metal presses
• Machine tools
• Fans and blowers
• Forging presses
• Bending rolls
• Boilers
• Injection molding machines
• Turbines

Electric motors are used throughout numerous fields, from petrochemicals to mining, cement production, sugar plants, and many other industries.

Since industrial AC motors are used in high-wear applications, they require thorough and proactive maintenance. Scheduling AC motor maintenance at regular intervals ensures the equipment receives the service it needs to prevent future breakdowns. Despite the ruggedness of their design, continuous, weekly, monthly, semiannual, and annual preventative procedures should all be performed.

Continuous Monitoring

Continuous monitoring of electric motors has become increasingly popular in industrial applications for several reasons:

• Improved maintenance: Continuous monitoring can detect early signs of wear and tear, allowing for proactive maintenance instead of reactive maintenance. This can increase the lifespan of the motor and reduce downtime, repair costs, and unplanned shutdowns.
• Increased efficiency: Monitoring can identify inefficiencies and irregularities in the motor’s operation, such as misalignment or excessive vibration, allowing for adjustments to be made to improve efficiency and reduce energy consumption.
• Enhanced safety: Continuous monitoring can detect potential safety hazards, such as excessive heat or abnormal vibrations, which can lead to catastrophic failures. This can help prevent accidents, injuries, and equipment damage.
• Cost savings: Early detection of issues can prevent major failures, resulting in cost savings associated with unplanned downtime, repair costs, and lost production.
• Smart manufacturing: Continuous monitoring is a key component of the Industry 4.0 concept, which aims to create smart factories where machines communicate and operate autonomously. This technology allows for real-time data collection, analysis, and feedback, allowing for predictive maintenance and improved overall equipment effectiveness.

Overall, continuous monitoring of electric motors can lead to improved reliability, efficiency, safety, and cost savings in industrial applications.

Weekly Maintenance

Since industrial AC motors are used continuously, they can experience significant wear in a relatively short amount of time. To ensure they remain in optimal condition, weekly inspections should include:

• Checking motor and bearing temperatures
• Verifying cleanliness
• Inspecting the fan, junction box, and cables
• Listening for unusual sounds during operation
• Visually inspecting the casing for any wear

Monthly Maintenance

Monthly maintenance on AC motors should include a more in-depth performance analysis to prevent emerging problems. Key monthly maintenance tasks include:

• Inspect and replace any worn brushes (for slip-ring motors)
• Check operating speeds
• Measure amperages
• Remove, clean, and replace oil in the sleeve bearings
• Perform vibration analysis
• Clean brushes, commutator, and windings

Biannual and Annual Maintenance

To prevent larger issues, more invasive maintenance tasks should be performed once or twice per year. These tasks include:

• Testing insulation
• Inspecting commutator and armature coil connections
• Checking footing and mounting

Renown Electric offers customized preventative maintenance programs as well as a Total Care Support Cost plan for outsourcing all ongoing predictive and preventative maintenance at an affordable price. Our maintenance services include:

• Dynamic balancing: This service corrects imperfections in a rotor’s rotational axis. Dynamic balancing measures and calibrates rotating equipment before an imbalance causes a serious problem, improving performance and extending equipment lifespan.
• Infrared thermography: This allows us to create a visual representation of heat distribution to verify normal operation or detect anomalies before they cause system damage.
• Laser alignment: Since misalignment can cause irrevocable damage, our advanced laser alignment system is critical for accurately identifying misaligned components, lowering vibrations, reducing energy consumption, and more.
• Oil analysis: We can identify electric motor wear and contamination by analyzing oil samples for impurities.
• Vibration analysis: Unwanted vibrations within motors cause wear and lead to high repair costs. Our vibration analysis services monitor your equipment’s internal condition and prevent future mechanical failure.
• Winding analysis: With winding analysis, we can discover electrical problems while they’re in the early stages and perform the necessary repairs to prevent unplanned downtime.
• Motion amplification monitoring: Our proprietary video processing algorithm amplifies subtle movements to visualize complex vibration problems.