What is the difference between dynamic and static balancing of a motor rotor?
Motor rotor dynamic balancing machine is an indispensable equipment for all motor manufacturers, which is very important to improve the quality of motor rotors. It is an effective way to reduce the operating noise of the motor by detecting and correcting the dynamic balance of the motor rotor. In the design of rotor dynamic balance correction process, it is the key to determine the total residual unbalance of the motor rotor and distribute the total residual unbalance to several correction planes. However, it should be noted that the dynamic balancing of the rotor section during the assembly process is equally important.
So, what is the difference between the dynamic balance and the static balance of the rotor?
Static balance refers to the balance correction of the rotor on one of the correction sides, and the remaining unbalance after correction needs to ensure that the rotor is within the specified range of the allowable unbalance when it is static, so it is also called single-sided balance. On the contrary, dynamic balancing is to balance the rotor on two correction fronts at the same time, and the remaining unbalance after correction needs to ensure that the rotor is also within the specified range of allowable unbalance when it is dynamic, so it is also called double-sided balance.
In addition, dynamic balancing machines are also divided into automatic balancing machines and manual balancing machines. The horizontal double pendulum frame of the automatic balancing machine adopts a hard support design, which can be accurately positioned, and the amount is accurate and the measurement is accurate, which can significantly improve the work efficiency. On the other hand, the equipment structure of the manual balancing machine may not be coordinated enough and the operation is not convenient enough. Operators may need to find their own angles, which can lead to misalignment, inefficiencies, longer measurement cycles, and other issues.
For standard motor manufacturers, in the production and processing process, it will be ensured that each part of the rotor part is in a balanced state, which can not only effectively improve the rotor balance accuracy, but also help to ensure the interchangeability of related parts. One of the most important components to note here is the fan, which rotates in sync with the rotor. Therefore, the balance of the fan itself is particularly important. For most motor fans, the static balance is usually carried out by deduplication, and the rotor is dynamically balanced without a fan. Some motor manufacturers, especially those with in-rotor fans, will install the fan before the rotor dynamic balancing, and carry out a comprehensive calibration balance during balancing. From a process point of view, this approach has its justification. However, there may be significant limitations for later maintenance and the interchangeability of parts.
Why do I need to balance the rotor?
Ideally, the pressure on the bearing should be the same as when rotating and not rotating, and such a rotating body is considered to be a balanced rotating body. However, in actual engineering, due to a variety of factors (such as uneven material, blank defects, processing and assembly errors, asymmetrical geometry, etc.), when the rotary body rotates, the centrifugal inertia force generated by each tiny particle on it cannot cancel each other. The centrifugal inertial force is transmitted to the machine and its foundation through the bearing, causing vibration and noise, accelerating the wear of the bearing and shortening the mechanical life. In severe cases, it can even lead to devastating accidents. Therefore, the rotor must be balanced to a permissible balancing accuracy level or to reduce the amplitude of the mechanical vibrations it generates to a permissible range.
There are many factors that cause rotor imbalance, such as: unevenness of rotor material, unbalance of coupling, asymmetry of keyway, rotor machining error, corrosion, wear and thermal deformation of rotor during movement, etc. These unbalances are generally random and uncontrollable, and need to be measured and corrected by gravity tests (static equilibrium) and rotational tests (dynamic balancing) to reduce them to the permissible range. At present, the most widely used balancing method is the process balancing method and the on-site dynamic balancing method of the whole machine.