Analysis of Differences Between Standard Motors and Variable Frequency Motors and Evaluation of Replacement Timing

Global leading pump manufacturer

• Abnormal temperature rise and high heat: The non sinusoidal PWM waveform output by the frequency converter contains a large number of "high-order harmonics". These harmonics enter the ordinary motor, causing a significant increase in copper and iron losses, resulting in abnormal heating of the motor during operation.
• Accelerated breakdown of insulation system: The pulse voltage spikes generated by the frequency converter will generate extremely high electrical stress between the windings of ordinary motors. The insulation level of ordinary motors is usually low, and long-term exposure to this impact can easily lead to inter turn short circuits or ground breakdown.
   
• The cliff like decline in equipment lifespan: Long term operation in high temperature and high electrical stress environments will accelerate the aging of the mechanical bearings, lubricating grease, and internal coil insulation of the motor, leading to a sharp reduction in the service life of the motor and a high risk of sudden burnout, resulting in unpredictable shutdown losses and safety hazards.

• Coaxial integrated heat dissipation limitation: Ordinary motors generally adopt a "coaxial integrated fan" design, which means that the heat dissipation fan is directly installed on the motor spindle, and its rotational speed is completely synchronized with the motor's operating speed.
• Wind cooling is only sufficient to cool itself: when the frequency converter reduces the system frequency (in Hertz), the motor spindle speed decreases proportionally. Due to the fact that the fan airflow is proportional to the square or cubic of the rotational speed, a decrease in rotational speed can lead to a geometric reduction in the amount of heat dissipation airflow. At this time, the wind can only barely cool itself when there is no load or extremely light load.
• The core heat generation point is still high: although the motor speed slows down at low Hertz, as mentioned in Q1, the electromagnetic heat generation caused by harmonics has not decreased. The heat dissipation ability drops sharply, while the internal heating points (such as the winding center) continue to generate high heat, resulting in severe heat accumulation and continuous temperature rise, becoming a fatal injury to the burnt motor.

• Wide frequency range adjustable Hertz: Variable frequency motors can freely adjust their speed within a wide frequency range (such as 5Hz-100Hz) according to actual process requirements. Its electromagnetic design has been specifically optimized for harmonic resistance, fundamentally suppressing the generation of excess heat.
• Satisfy different working conditions without affecting the service life: Whether the production line requires long-term low-speed high torque output or high-frequency fast flow, the variable frequency motor can easily cope. It adopts a higher level of insulation system (such as F-class, H-class, and equipped with specialized anti corona measures), which can perfectly withstand the high-frequency pulses of the frequency converter, and does not affect the service life of the motor when used at various frequencies.
• Independent forced ventilation cooling system: The variable frequency motor abandons the integrated coaxial fan and uses an "independent axial fan" for heat dissipation. The power supply of this fan is completely independent of the main power supply of the motor. No matter how low the Hertz of the main motor is reduced due to speed regulation, or even when it is close to stopping, the cooling fan still maintains full speed operation, providing a constant large air volume for blowing, ensuring that the temperature of the motor's hot spot is always within an absolutely safe range.

• Optimize the starting method to achieve impact free soft start: Traditional power frequency direct start can result in up to 5-7 times the impact current. By controlling the cabinet with a frequency converter, the pump system can achieve a "smooth and shock free start" starting from 0Hz and 0V. This not only greatly protects the safety of the power grid, but also completely eliminates the "water hammer effect" that damages pipelines during traditional start-up, providing excellent protection for the impeller and mechanical seal of the pump.
• Accurately responding to process requirements and achieving on-demand flow: The control cabinet can collect real-time data on pipeline pressure, flow rate, etc., and instruct the frequency converter to accurately adjust the frequency (Hertz) of the motor. During periods of low demand, the system can safely operate at a reduced frequency, achieving significant energy savings while ensuring smooth and stable process flow.
• Release the maximum circulation potential of the system: When the backend is replaced with a highly reliable variable frequency motor, the system completely breaks free from the constraints of "low frequency operation and fear of burning the machine". Pump equipment can safely flow continuously for 24 hours at different frequencies and operating conditions, enabling the entire fluid delivery network to achieve the highest operational efficiency and flexibility.