Patent Application
20140166844
This disclosure relates generally to electric motors, and, in particular, to support braces for electric motors.
Electric motors are used in various household, office, automotive, and industrial applications. A typical electric motor includes a rotor surrounded by an electromagnet, called a stator. When varying electrical energy is applied to the stator, a magnetic field is generated that produces a torque that spins the rotor. The rotor includes an output shaft that connects to an output device, such as a pump, fan, belt, or gear, to operate the device with the rotational output of the motor. A vertically mounted electric motor is one in which the output shaft is oriented vertically to enable the output shaft to be coupled to an output device positioned above or below the motor. Vertical motors rest on a stand, which is configured to provide a stable platform for the motor and output device. Horizontally oriented motors, on the other hand, are mounted such that the output shaft extends from the motor housing horizontally and the output shaft couples to an output device located next to the horizontal motor.
During operation of an electric motor, the rotating components of the motor generate vibrations that resonate at various frequencies. A motor and housing system has a resonance frequency (also known as a reed-critical frequency or “RCF”), which is a function of the mass, distribution of the mass, and base geometry of the motor and housing system. If the frequency of the vibrations in the system is close to or the same as the RCF of the motor system, the vibrations are amplified through the motor system, generating loud noises and potentially resulting in mechanical issues with the motor.
The frequency of the vibrations and the RCF can be calculated in a motor based on the operating conditions of the motor and the geometry of the system. Thus, a motor base is typically designed such that the RCF is not near the vibration frequencies. However, in some instances, issues develop after installation of a vertical motor that arise from changed operating conditions or erroneous calculations. One solution to RCF vibration issues involves replacing the motor with a motor of a different size, which produces different vibration frequencies and has a different RCF. Another solution is to replace the motor stand, which also alters the RCF of the motor system. However, both solutions require removing the motor from the stand. Vertical motors in industrial applications are often very large and heavy, and heavy equipment is required to remove the motor from the stand. Thus, replacing the motor or stand can be very expensive. Consequently, an improved solution to RCF vibration issues is desirable.
In one embodiment a brace dampens resonant vibration of an electrical motor mounted to a stand. The brace comprises a first flange configured to mount to an electrical motor housing, a second flange configured to mount to a supporting fixture of the electrical motor, and a member extending between the first flange and the second flange. The member is configured to increase a stiffness of the electrical motor and supporting fixture to modify a resonance frequency of the electrical motor.
In another embodiment a method has been developed to dampen resonant vibration of an electrical motor. The method includes mounting a first flange of a brace to an electrical motor housing and mounting a second flange of the brace to a supporting fixture of the electrical motor. The second flange is connected to the first flange by a member extending between the first and second flanges, and the member is configured to increase a stiffness of the electrical motor and supporting fixture to modify a resonance frequency of the electrical motor.
In yet another embodiment, a system enables dampening of resonant vibration of an electrical motor. The system comprises a plurality of braces, each of which includes a first flange configured to mount to an electrical motor housing, a second flange configured to mount to a supporting fixture of the electrical motor, and a member extending between the first flange and the second flange. The member of each brace is configured to increase a stiffness of the electrical motor and supporting fixture to modify a resonance frequency of the electrical motor. Each brace in the plurality of braces is mounted to the electrical motor housing and the supporting fixture at a position that is different than a position at which the other braces of the plurality of braces are mounted to enable the members of the plurality of braces to stiffen the electrical motor around a perimeter of the electrical motor to modify the resonance frequency of the electrical motor.
As used herein, the term “supporting fixture” refers to a structure that supports at least a portion of the electrical motor. The supporting fixture can be a mounting plate positioned on or beneath a motor housing, a portion of the motor housing, a motor frame, a motor stand, or a foundation or other structure on which the motor is installed.
The motor stand 140 includes a mounting plate 144, a plurality of fixed supports 148, and an output shaft casing 152. The motor stand 140 is configured to enable the motor system 100 to be mounted on an output device, for example a pump, to which the motor delivers rotational motion. In other embodiments, the motor stand can be configured to mount the output device to the ground or a foundation. The output shaft casing 152 surrounds an output shaft (not shown) of the motor in the region between the motor housing 120 and the output device. A plurality of fixed supports 148 positioned around a circumference of the motor system 100 extend from the mounting plate 144 to the housing base 128 to connect the mounting plate 144 and housing base 128 and provide structural support for the housing base 128.
Referring to
In the illustrated embodiment, each of the first 220 and second 240 flanges include two apertures 224 and 244, respectively. Apertures 224 are configured to enable a securing member 228, for example a bolt, to pass through the aperture 224 and into a threaded hole formed in the housing base 128 to affix the first flange 220 to the housing base 128. Likewise, apertures 244 are configured to enable a securing member 248 to pass through the aperture 244 and into a threaded hole formed in the mounting plate 144 to affix the second flange 240 to the mounting plate 144. In other embodiments, more or fewer apertures and securing members can be used to affix the brace to the housing base and mounting plate. In yet another embodiment, the brace does not include apertures, but is affixed to the housing and mounting plate by other methods, such as welding, for example.
As illustrated in
When a vibration issue is discovered in a vertically mounted motor, such as motor system 100, the braces 200 are installed between the housing base 128 and the mounting plate 144 to alter the stiffness, and thus the RCF, of the motor system 100. Each brace 200 of the illustrated embodiment is installed by placing the brace 200 against the motor housing 120 and mounting plate 144. Holes are drilled into the motor housing 120 and mounting plate 144, using the apertures 224 and 244 in the brace 200 as guide holes. The holes in the motor housing 120 and mounting plate 144 are tapped to enable securing members 248 to be inserted through the apertures 224 and 244 into the holes in the motor housing 120 and mounting plate 144, respectively, to secure the brace 200 to the motor housing 120 and mounting plate 144. As noted above, any suitable number of securing members can be used to affix the brace to the housing base and mounting plate. In other embodiments, the brace is affixed to the housing and mounting plate by other methods, such as welding, for example.
Providing the braces 200 on the motor system 100 serves to stiffen the bending moment of the motor stand 140 and the lower part of the motor housing 120. In response to the stiffened bending moment, the fixed supports 148 of the motor stand 140 bend less with the vibrations, altering the RCF of the system. The critical frequency is altered by a predetermined amount to ensure that the RCF of the system is outside the range of vibration frequencies, avoiding amplification of the system vibrations. Although
The second brace 500 includes a first brace portion 504 and a second brace portion 508. The first brace portion 504 includes a first flange 520, a second flange 540, and a first connecting member 560, while the second brace portion includes a third flange 524, a fourth flange 544, and a second connecting member 564. The first flange 520 is configured to be affixed to the housing ring 316, while the second flange 540 is affixed to a supporting structure (not shown), such as a foundation, motor stand, or other structure on which the motor is mounted. Likewise, the third flange 524 is affixed to the housing ring 316, while the fourth flange 544 is affixed to the supporting structure. The second flange 540 and fourth flange 544 are connected, such that the first brace portion 504 and the second brace portion 508 form a single brace 500.
The first brace 400 and the second brace 500 operate in substantially the same manner as the brace 200 described above with reference to the vertically mounted motor. Providing the braces 400 or 500 on the motor housing 300 serves to stiffen the bending moment of the motor and motor housing 300. In response to the stiffened bending moment, the housing moves less with the vibrations generated by the motor, altering the RCF of the system. The critical frequency is altered by a predetermined amount to ensure that the RCF of the system is outside the range of vibration frequencies, avoiding amplification of the system vibrations.
The first brace 400 and the second brace 500 can be affixed to the motor housing 300 and/or the support structure (not shown) in any suitable manner. For example, the flanges of the braces 400 or 500 can be attached by inserting a threaded member through an aperture in the flange, or the flanges can be welded to the housing or support structure. Furthermore, the reader should appreciate that the support braces can be suitably mounted to any number of different structures on the motor housing or the motor support structure to alter the RCF of the motor system, as long as the support brace alters the stiffness of the motor system and alters the RCF of the motor system to reduce vibrations in the system.
It will be appreciated that variations of the above-disclosed apparatus and other features, and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, which are also intended to be encompassed by the following claims.
