Mechanical Performance Requirements of Electric Motors: What Do They Involve?

Mechanical Performance Requirements of Electric Motors: What Do They Involve?

Electric motors must meet both electrical and mechanical performance requirements. While electrical characteristics—such as insulation performance, current, and voltage—are often well understood and emphasized, the mechanical characteristics of motors are frequently overlooked. This is especially true among motor manufacturers who rely heavily on outsourcing key components, resulting in reduced focus on mechanical performance standards.

To ensure the mechanical safety and reliability of a motor during operation, its mechanical strength is evaluated through eight specific tests. These mechanical tests include:

Overspeed Test

Short-Time Over-Torque Test

Impact Test

Terminal Box Static Pressure Test

Conduit Entry Thread Strength Test

Terminal Block Strength Test

Lifting Device Test

Flexible Cable Clamping Test

Each of these tests serves a different purpose. Some can be conducted during the component manufacturing stage, while others require testing on the fully assembled motor, and even under powered conditions.

For instance, after the overspeed test, the rotating parts of the motor must show no permanent deformation or defects that could hinder operation. This test is particularly critical for wound rotor motors, whose design inherently limits their rotational speed. Additionally, after passing the overspeed test, the rotor winding must be able to withstand the specified dielectric strength test.

For multi-phase induction motors and DC motors, regardless of their duty type or structure, the motor must endure a short-time over-torque test at no less than 1.6 times the rated torque for 15 seconds, without any sudden changes in speed or stalling.

The impact test applies mainly to motors with non-metallic enclosures. After testing, the motor must show no functional damage and must maintain proper electrical clearance and creepage distances. This is also why, in many export markets, customers require terminal boxes to be made of cast iron or thick steel plates, rather than the thin steel sheets commonly used in China—primarily due to tougher environmental and application demands abroad.

The lifting device test must also be conducted on the complete motor assembly. This test ensures the safety of motor handling and installation. Lifting eyes and brackets must not only meet load-bearing requirements but also ensure proper directional balance during lifting operations.