English
AC electric motors used on fans typically consist of windings, bearings, and other internal mechanical parts. All those parts need to be enclosed by what's referred to as a frame, which serves a dual purpose. The frame protects the internal parts, but at the same time, it allows heat generated within the windings to be dissipated from the motor. Some motor frames also have external fins that are used to help dissipate the heat.
For the sake of this blog post, let's consider fractional horsepower fans from ¼ hp through 200 hp, which represents about 80% of all motors used on industrial and commercial fans. The range of available sizes and standard NEMA frames is starting to grow. The common types of frames as defined by NEMA include:
Open Drip Proof (ODP)
This type of motor has an open frame that allows air to pass through the motor windings for ventilation. The openings on the top side of the motor are shielded and protected from anything that could drip into the motor at angles ranging from 0 to 15 degrees (from above). These would typically be used for belt drive fans in relatively clean environments. Oftentimes, the motor would have a secondary fan motor cover to provide additional protection.
Totally Enclosed Air Over/Airtight (TEAO)
This motor has a dust-tight frame or enclosure. It is typically installed in the airstream, and the air movement generated by the fan passes over the motor to provide cooling. TEAO motors would be used in areas with direct drive where the motor is in the airstream.
Totally Enclosed Non-Ventilated (TENV)
This is not an airtight motor. There is no provision in terms of openings or external fans for cooling, so this type of designation relies on simple convection for the heat to dissipate from the motor frame. TENV motors would be used in a clean air environment in the airstream application.
Totally Enclosed Fan Cooled (TEFC)
This motor is similar to the TENV, but it has an external fan mounted to the shaft that operates at the same speed of the fan motor shaft to cool the frame of the motor. TEFC motors would typically be used out of airstream, or in the airstream with either direct or belt drive. Due to its configuration, TEFC motors have quite a bit of versatility.
Totally Enclosed Severe Duty
These motors have enhancements like higher quality seals and/or stainless steel shafts. Special coatings on the frame allow them to be used with more sustainability in heavy industrial environments like chemical, oil, gas and forestry products. An example of a widely accepted designation for a totally enclosed severe duty application would be an IEEE 841 compliant design.
Totally Enclosed Wash Down (TEWD)
This motor is an enhancement above the TENV, TEAO, or TEFC design in that it is suitable for high pressure wash-down or applications where there is high humidity or moisture. It can be used in belt drive or direct drive fan applications, and is available as an enhancement or upgrade to a TEAO, TENV, TEFC, or severe duty enclosure.
Explosion Proof
Explosion proof motor categories are rather interesting. These motors are labeled for classes: Class 1 is gases and vapors, and Class 2 is combustible dust. Within those classifications, there are groups such as A, B, C, and D. Those groups identify the specific type of vapor or dust in which the motor is suitable to be applied.
The NEMA explosion proof class and group listings only apply to the electric motors and switch gear. Fans typically are not sold as explosion proof devices. Instead, they are typically sold as spark resistant devices. There are three different types of spark resistant fan constructions available. To identify and explain these types, you can refer to AMCA Standard 99, 2010. Any of these motors may or may not be compatible for VFD (variable frequency drive) duty.
Motor efficiencies and the legal requirements for minimum motor efficiencies in many countries have evolved since the mid-1990s. They are set forth by the energy authorities in the United States, Canada, and the European Union, for example.
M.K Plastics can explain your motor choices for your critical service fan equipment. Feel free to contact us today for more information.
MKPlastics005-020 Transcription
Shayla: You are listening to the MK Plastics Podcast and I'm talking today with Keith Lins who is the Vice President of US Sales and Marketing at MK Plastics, and Keith, today can you tell us about what types of AC motors are commonly used on industrial and commercial fans?
Keith: Well, AC electric motors used on fans typically consist of windings, bearings, and other mechanical parts inside and those parts need to be enclosed by what's referred to as a frame and that frame protects the internal parts, but at the same time, heat generated within the windings must be dissipated from the motor through the frame. Some motor frames have external fins that are used to help dissipate the heat. Let's consider for discussion fractional, say one quarter horsepower through 200 horsepower which represents about 80 percent of all the motors used on industrial and commercial fans. The range of available sizes and standard NEMA frames is starting to increase and grow. So the common types of frames as defined by NEMA include the following: ODP which stands for open drip proof and this type of motor has an open frame that allows air to pass through the motor windings to ventilate it and the openings on the top side of the motor are shielded and protected from anything that could drip into the motor at an angle of plus or minus 15 degrees from above so these would typically be used for belt drive fans in relatively clean environments and oftentimes the motor would have a secondary fan motor cover on it just to give additional protection to the motor. The next class is TEAO which is totally enclosed airtight. This motor has a dust tight frame or enclosure. It is typically installed in the airstream and the air movement generated by the fan passes over the motor to cool the motor. So that would be used in areas where oftentimes direct drive with the motor in the airstream. The next type is TENV which stands for totally enclosed non-ventilated. This is not an airtight motor. There is no provision in terms of openings or external fans for cooling, so this type of design relies on simple convection for the heat to dissipate from the motor frame. This would be used in a clean air environment in the airstream application. The next definition is TEFC which is totally enclosed fan cooled. This is like the totally enclosed non-ventilated, but it has an external fan mounted to the shaft that operates at the same speed of the fan motor shaft to cool the frame of the motor. This would be typically used out of airstream or it could be used in the airstream in either direct or belt drive. This TEFC motor has quite a bit of versatility. The next type would be a totally enclosed severe duty. These motors have enhancements like higher quality seals, stainless steel shaft, special coatings on the frame that allow them to be used with more sustainability in heavy industrial environments like chemical, oil, and gas and forestry products. An example of a widely accepted designation for a totally enclosed severe duty application would be an IEEE 841 compliant design. Another commonly used motor enclosure is TEWD, which stands for totally enclosed washdown duty. This motor is an enhancement above the TENV or TEA or TEFC design in that it is suitable for high pressure washdown or applications where there is high humidity or moisture. It can be used in belt drive or direct drive fan applications and is available as an enhancement or upgrade to a totally enclosed air over non-ventilated, fan cooled, or severe duty enclosure. Explosion proof motor categories are rather interesting. These motors are labeled for classes, typically either class one which is gases and vapors or class 2 which is combustible dust and within the classifications, there are groups such as A, B, C, D, and the groups specifically identify the specific type of vapor or dust that this motor is suitable to be applied in. Now, the NEMA explosion proof class and group listings apply only to the electric motors and switch gear. Fans typically are not sold as explosion proof devices. Fans are typically sold as spark resistant devices and there are three different types of spark resistant construction available. There are three different types of spark resistant fan construction available and to identify and explain these types, you can refer to AMCA standard 99, 2010. Any of these motors may or may not be compatible for VFD or variable frequency drive duty. Motor efficiencies and the legal requirements for minimum motor efficiencies in many countries have evolved since the mid-'90s. They are set forth by the US, Canadian, EU, these requirements are set forth by the energy authorities in the United States, Canada, and the European Union, for example. MK Plastics can explain your motor choices for your critical service fan equipment. Feel free to contact us.
Shayla: And that contact number for MK Plastics is 888-278-9988.