1. The speed regulation range of a high-voltage frequency converter is 0 to 100. If the mechanical strength of the motor and load allows and the motor is not overloaded, the frequency converter can also make the machine run at overspeed. The speed regulation range of a hydraulic coupling is generally 40 to 95, that is, the high-speed section causes a speed loss of about 5, which affects the output of the unit. The lowest speed of a hydraulic coupling is generally only 40% of the rated speed. In some cases, it cannot meet the speed regulation needs and sometimes affects the further realization of energy-saving benefits.
2. High-voltage frequency converters have high efficiency (greater than 96%) throughout the entire speed range; while hydraulic couplings have lower efficiency at lower speeds, resulting in significant losses and greatly reducing the energy-saving effect of speed regulation.
3. High-voltage frequency converters enable true soft starting of motors and load machinery, completely solving the starting shock problem. If the process requires it, the motor can be started repeatedly in a short period of time. In contrast, hydraulic couplings cannot solve the motor starting problem. The motor is still directly started, requiring a starting device, and the starting shock is large. It also cannot be started frequently.
4. When using a high-voltage frequency converter to modify the speed of a motor, simply disconnect the original switch and motor connection cable, add the frequency converter, and leave the connection between the motor and the machine unchanged. No foundation needs to be modified, and there are no site restrictions. However, when using a hydraulic coupling for speed modification, the hydraulic coupling must be inserted into the connecting shaft between the motor and the machine. This requires moving and re-pouring the equipment foundation, which may not be feasible in some places.
5. Using a high-voltage frequency converter to modify the speed of the motor means that if the frequency converter fails, the motor can still be directly connected to the power grid without causing production loss. However, the hydraulic coupling is the link between the motor and the machinery. If the hydraulic coupling fails, the load machinery will not be able to operate, and the machine will have to be shut down for repair of the hydraulic coupling, resulting in production loss.
High-voltage frequency converters are high-tech equipment with high reliability and are basically maintenance-free; while hydraulic couplings are mechanical equipment that contain multiple systems such as oil circuits and water circuits, have a high failure rate, require a large amount of maintenance, and result in a shortening of effective production time.
6. High-voltage frequency converters do not increase costs due to motor speed, while low-speed, high-capacity motors using hydraulic couplings for speed regulation will have significantly increased costs, and in some cases, may even be impossible to achieve.
7. For general motor speed regulation, the initial investment for a high-voltage frequency converter is larger than that for a hydraulic coupling, but the frequency converter requires almost no operating costs afterward. Hydraulic couplings, on the other hand, require frequent maintenance, including maintaining a dedicated maintenance team and regularly paying for water and oil changes, resulting in higher operating costs.
8. High-voltage frequency converters have a high level of intelligence, high speed regulation accuracy, and can directly operate in closed loop, improving the automation level of the factory, reducing the number of workers, improving the working environment, and reducing workload; while hydraulic couplings have poor speed regulation accuracy, cannot be considered automatic control, cannot interface with computers, and leak water and oil, often resulting in a dirty and unpleasant environment.
In summary, if users have equipment that requires speed adjustment, from our perspective, unless funds are particularly tight, we recommend against using hydraulic couplings.
