Rotor dynamic balancing is an essential and critical quality control point for all motor manufacturers. For high-voltage motors, low-voltage high-power motors, and other motors that run with fans, the installation of fans is involved. However, a very important point is how to achieve dynamic balance of the rotor part during the assembly process.
For reputable motor manufacturers, the production process ensures that all parts of the rotor are in a balanced state. This effectively improves the rotor's balance accuracy and also guarantees the interchangeability of related parts.
This involves a very important component: the fan that rotates synchronously with the rotor. Therefore, the balance of the fan itself is particularly important. For most motor fans, static balancing is performed by removing the weight, and the fan is not used during rotor dynamic balancing. However, some motor manufacturers, especially for motors with internal rotor fans, install the fan before rotor dynamic balancing and perform comprehensive dynamic balancing during the balancing process. From a manufacturing perspective, this has its rationale, but it severely limits later maintenance and the interchangeability of parts.
Expanding knowledge about electric motors
1. Why is it necessary to perform dynamic balancing on the rotor?
Various drive shafts, main shafts, fan impellers, water pump impellers, cutting tools, electric motors, and turbine rotors are collectively referred to as rotating bodies. Ideally, the pressure exerted on the bearings is the same whether the rotating body is rotating or not; such a rotating body is a balanced rotating body. However, in engineering applications, various rotating bodies, due to factors such as uneven material composition, defects in the blank, errors in processing and assembly, and even asymmetrical geometric shapes in the design, cause the centrifugal inertial forces generated by each tiny particle on the rotating body to not cancel each other out during rotation. These centrifugal inertial forces act on the machinery and its foundation through the bearings, causing vibration, generating noise, accelerating bearing wear, shortening the machine's lifespan, and in severe cases, leading to destructive accidents. Therefore, it is necessary to balance the rotor to achieve the allowable balance accuracy level, or reduce the resulting mechanical vibration amplitude to within the permissible range.
Many factors can cause rotor imbalance, such as: non-uniformity of rotor material, imbalance of couplings, asymmetry of keyways, rotor machining errors, and corrosion, wear, and thermal deformation generated during rotor operation. The imbalance caused by these factors is generally random and cannot be calculated. It needs to be measured and corrected through gravity tests (static balancing) and rotational tests (dynamic balancing) to reduce it to an acceptable range. The most widely used balancing methods are process balancing and on-site dynamic balancing of the entire machine.
2. The difference between rotor dynamic balancing and static balancing
●Static balancing: The balancing is performed on one of the correction planes of the rotor. The remaining unbalance after correction is to ensure that the rotor is within the specified range of allowable unbalance when it is static. Therefore, static balancing is also called single-plane balancing.
● Dynamic balancing: The rotor is balanced on two correction surfaces at the same time. The remaining unbalance after correction is to ensure that the rotor is within the specified range of allowable unbalance when it is in motion. Therefore, dynamic balancing is also called two-sided balancing.
Disclaimer: This article is a reprint. If it involves copyright issues, please contact us promptly for deletion (QQ: 2737591964). We apologize for any inconvenience.
