Basic information for selecting an electric motor

Why should we pay attention when selecting an industrial electric motor

Correctly selecting an industrial electric motor can provide several benefits, including:

1. Greater energy efficiencyIf an electric motor is selected correctly with adequate efficiency, energy consumption can be significantly reduced, resulting in long-term cost savings.
2. Longer engine lifeWhen selecting an electric motor suitable for the specific application, motor wear can be reduced and its service life extended.
3. Greater securitySelecting the correct type of electric motor for a specific application can improve workplace safety by reducing the risk of failures and accidents.
4. Cost reductionThe correct selection of an electric motor can help reduce maintenance and repair costs, as well as long-term energy costs.
5. Performance improvementBy selecting an electric motor appropriate for the specific application, the overall system performance can be improved, which can increase productivity and efficiency.

Information to consider when selecting an electric motor 

To select or properly understand an engine, you normally take into account the characteristic data found on the plate that is usually on the engines.

When sizing an industrial electric motor, it is important to consider the following basic data:

• PowerThe power required for the specific application of the motor, measured in horsepower (HP) or kilowatts (kW).
• LockdownThe type of enclosure required for the specific application of the motor, which can be open, enclosed, or explosion-proof.

  On the motor plate, in addition to showing the power in hp (kilowatts), the type of enclosure is also detailed, which refers to the type of construction in industrial electric motors. As we have said, there are three types of enclosures: open motors, closed motors, and explosion-proof motors. One of the basic pieces of information needed when selecting a motor is the area in which the motor will operate.

  The environment in which the electric motor will operate defines the type of enclosure, and logically, the type of enclosure is related to the price. An open motor and a closed motor have a price difference, while a more expensive motor is an explosion-proof motor, as it has characteristics for working in areas classified as hazardous or explosive. Therefore, when selecting a motor, it is necessary to know the area in which it is to be used.

• Frame sizeThe size of the motor frame required for the specific application.

  The frame size is related to the power, as a larger size means greater power in the motor. This depends on the conditions where the motor will operate, such as altitude, ambient temperature, or variations in voltage frequency. To select a motor correctly, all these environmental conditions must be taken into account.

• EfficiencyThe efficiency level required for the specific application of the engine, measured as a percentage.

  The efficiency level of an electric motor is a very important point when selecting industrial motors. Motor manufacturers are currently designing and manufacturing motors with the highest possible efficiency. In this region, North America (Mexico, the United States, and Canada), the efficiency level used is the highest, which is NEMA Premium efficiency. With NEMA Premium efficiency, we are talking about more energy-saving motors.

• Rotational speedThe required rotational speed for the specific motor application, measured in revolutions per minute (RPM).

  The speed of revolutions per minute or the number of poles is another piece of information to consider, depending on the speed required for the activity the motor will be used for.

• Frequency and number of phasesThe frequency and number of phases of the electrical supply to be used to power the motor.

  For the frequency and number of phases, two frequencies are used, 50Hz and 60Hz. This is already included by default and does not need to be requested as something special.

• VoltageThe voltage required for the specific application of the motor.

  Voltage is something that needs to be requested and specified carefully, as there are regions in the same country where different voltages can be used. Motor manufacturers can produce units according to the need or the area where a different voltage is required, including low-voltage motors or voltages up to 565 volts.

• Insulation classThe insulation class required for the specific motor application, measured in degrees Celsius.

  Another important point when selecting industrial electric motors is the insulation class. When we talk about insulation in electric motors, we are referring to the protection that the coils have and that is made of copper. The insulation serves to guarantee the good operation of the motor, and it basically consists of the varnish coatings that the coils have. Check here the Failing due to insulation in electric motors: how to measure and fix it.

  It is very important to consider that there are two factors that directly affect a motor's operational life: temperature and vibration. The insulation class is related to the internal motor temperature data, as the insulation is limited to a certain temperature.

• Power factorThe power factor required for the specific application of the motor, which is measured in percentage.

  The power factor in an electric motor is specified on the nameplate. It is usually represented by a number such as 1.00, 1.15, 1.25 up to 1.35. This means that the motor is designed and capable of working according to what the nameplate indicates. For example, if the motor has 1.15, which is the most standard, then it means that the motor is designed to work up to 15% above its rated power. If we have a 100 hp motor and a service factor of 1.15, in theory, we can consider that this motor can work up to 115 hp of power.

• CurrentThe current required for the specific motor application, measured in amps.

  Another important factor to consider when choosing electric motors is the current in amperes. The bearing that takes all the load and does all the work is the front bearing. In a horizontal motor, the rear bearing is a guide bearing that does no work. In vertical motors, the bearings that take all the load are the top ones, while the bottom acts as a guide.

• Bearing typeThe type of bearing required for the specific motor application.
• Type of lubricationThe type of lubrication required for the specific engine application.

  Lubrication in electric motors is fundamental for their proper functioning and to extend their lifespan. Some of the benefits of adequate lubrication in electric motors are:

  • Reduced friction: Proper lubrication reduces friction between engine parts, which decreases wear and reduces the chance of engine failures.
  • Corrosion protection: Lubrication protects the electric motor from corrosion and rust, which can damage motor parts and reduce efficiency.
  • Temperature reduction: Proper lubrication reduces the temperature of the electric motor, which in turn decreases the likelihood of overheating-related failures.
  • Increased energy efficiency: Proper lubrication reduces friction and temperature, which increases the energy efficiency of the electric motor, resulting in savings on electricity costs.

To identify the engines, it is necessary to know the model number and serial number; this way, you can tell when and where the engine was manufactured.

Wiring diagrams are another piece of data found on the motor control panel.

It is very important to keep engine plates in good condition, as these allow us to easily identify the internal characteristics of the engine.

Plan the selection of electric motors 

The selection of industrial electric motors is a critical process that requires careful planning to ensure the correct motor is chosen for each application. If an incorrect motor is selected, this can lead to additional costs and long-term performance issues. Therefore, it is essential that an appropriate selection of electric motors is made in industry.

One of the most important considerations we've seen in selecting an electric motor is the application for which it will be used. Remember that the type of application and its operating requirements can influence the selection of the motor type, speed, size, and other important aspects.

In conclusion, the selection of industrial electric motors is a critical process that requires careful planning and detailed consideration of a variety of factors. The right motor choice can significantly improve performance and energy efficiency, reduce operational costs, and prolong the motor's lifespan. Therefore, it is essential that an appropriate selection of electric motors is made in industry. You may be interested in:

• Problems and failures in three-phase motors: Types, Reasons and Solutions
• Overload faults in industrial electric motors and how to solve them
• Typical faults in industrial electric motors and how to fix them
• Repairing electric motors vs replacing them