Induction Motor Noise

Induction motors are the most popular motors in use nowadays. Motor sound can be a obstacle for most motor suppliers. So what leads to motor sound and what can be carried out to cut down the sound? In this short article we will explore in which motor sound arrives from and how it can be minimized.

The 3 fundamental forms of motor sound are:

one. Magnetic Sound
two. Bearing Sound
three. Unbalance Sound


The key supply for magnetic sound in induction motors arrives from power waves designed by the rotating magnetic subject. Considering that this subject is the automobile by which electricity is transmitted from the stator to the rotor, elimination of this sound is not doable. Even so, magnetic sound can be minimized by using numerous procedures:

one. Utilizing the suitable stator and rotor slot mixture
two. Building the stator and rotor lamination geometry
three. Making use of the appropriate coil pitch
four. Formulating the proper rotor skew

The appropriate range of stator and rotor slots is just one of the most significant facets of a silent motor style and design. This range also impacts producing expenditures. To maintain producing expenditures minimal, the quantity of stator slots must be the quantity ofoles situations the quantity of areas in just a offered body dimensions. This quantity of stator slots must be these kinds of that a well balanced winding can be accommodated. There are rarely any slot mixtures that are great having said that, about the yrs there have been some mixtures that have verified to be thriving. The pursuing normal procedures must be employed as a guidebook when creating the lamaintions:

a. The quantity of rotor slots must not equivalent the quantity of stator slots. Satisfactory efficiency has been attained when the quantity of rotor slots differs by the quantity of stator slots by 15 to 30%. b. To stay clear of useless factors or cogging, the big difference involving stator and rotor slots must not equivalent +/- quantity of durations situations quantity of poles c. To reduce sound and vibration the big difference involving the quantity of stator slots and rotor slots must not equivalent +/- one, +/- two, +/- (quantity ofoles +/- one) and / or +/- (quantity ofoles +/- two). For illustration: if you have a six pole motor and the stator lamination has 18 slots then the rotor laminations must not have the pursuing quantity of slots: 17, 19, 16, 20, 13, 23, 14, or 26.

When creating the stator and rotor lamination geometry, several parameters ought to be reviewed. A shut rotor slot will bring about significantly less permenace variation, having said that, thickness of the bridge ought to be reviewed to make certain the lamination does not saturate. The width of the stator slot opening must be stored to a minimum amount having said that you nonetheless will need it massive ample to insert the coils. The duration of the air hole also impacts permeability variation these kinds of that the bigger the hole the significantly less the variation. But maintain in brain, the air hole also is dependent on the other style and design standards these kinds of as electricity element and performance. The motor style and design engineer desires to just take into account all prerequisites when creating laminations.

Making use of the appropriate stator coil pitch is in addition significant. The stator coil pitch ratio must be chosen to give smaller pitch components for reduce get of air hole harmonics. The motor designer will will need to maintain this in brain when creating the winding. Skewing of both rotor or stator slots is a different way to cut down motor sound and offer sleek acceleration. The diploma of skew also impacts motor efficiency, hence the skew is restricted to efficiency parameters these kinds of as crack torque, setting up torque and setting up currents.


Bearing sound can be motivated by numerous components these kinds of as preload, shaft to bearing suits / tolerances, and bearing to bore suits / tolerances. The final decision to which bearing to use must generally rely on the software of the motor. It is really advised to require bearing manufactures when picking the bearing.

Right preloading is necessary to make certain the bearings operate sleek. As well a lot preloading will hurt the bearings. Exact same philosophy goes with the bearing suits to the motor shaft and housing and stop bell bores. Bearing manufactures have advised suits / tolerances to put into action all through the mechanical style and design of the motor .


Unbalance sound is designed by an unequal bodyweight distribution of the rotor assembly about the motor axis of rotation. It has been discovered that vacuum impregnation and / or encapsulation of motor stator windings has also assisted in coil vibration and sound. There are several techniques to cut down motor sound. All motor parameters ought to be taken into account when creating the device.

Source by Donna Kirk