Objectively speaking, variable frequency (VFD) starting effectively solves potential problems during motor starting, whether for fixed-frequency or variable-frequency motors . Essentially, VFD starting reduces the risk of winding overheating by controlling the starting current, which is beneficial to the motor itself, the driven equipment, and the power grid. However, some customers lack the necessary conditions for VFD starting and can only use fixed-frequency starting for certain fixed-frequency motors. This leads to situations where problems are not detected during manufacturing and testing but arise during application. In other words, VFD starting during testing may mask some issues encountered during application.

Therefore, regardless of whether the motor manufacturer has the capability for frequency conversion testing, the starting performance of power frequency motors should be verified according to the product's technical specifications. A friend of mine once shared a real-world case from their company: they supplied a batch of multi-speed variable pole motors to a customer. Conventionally, motors are started at low speeds, thus emphasizing starting torque at low speeds. However, upon arrival at the customer's site, the customer actually started the motors at high pole counts, revealing a starting failure. During the motor testing phase, because frequency conversion starting was used, the starting problem wasn't detected. In reality, the performance compliance of power frequency starting wasn't fully verified, leading to a mismatch between product performance and actual application.

Therefore, when ordering, designing, and testing motors, it is essential to fully understand the customer's actual application needs and avoid subjectively solving all problems based on conventional practices.

In addition, many variable frequency motors have serious electromagnetic noise problems in application. Some motor manufacturers only conduct tests at the rated frequency without considering the conventional frequency bands used in actual customer applications, which is also a common problem that leads to poor motor performance.