When choosing the start-stop control or frequency conversion regulation of the compressor of low temperature chiller according to the load fluctuation, multiple factors such as system load change, energy efficiency optimization, equipment life and control accuracy need to be comprehensively considered.

I. Compressor Start-Stop Control (ON/OFF Control)

Applicable scenarios

For small refrigeration equipment or systems with minor load variations, adopting intermittent operation (ON/OFF) control is a simple and feasible method. When the temperature reaches the set value, the compressor starts. When the temperature drops below the set value, the compressor stops running. However, this method is not recommended for use in high-power compressors because frequent starts and stops can lead to voltage fluctuations, shortened equipment lifespan, and high energy consumption.

Disadvantage

- Frequent start-stop wear equipment: When the compressor starts, the current impact is large. Long-term use will shorten the motor's lifespan.

Low load matching accuracy: Fixed output may lead to "a big horse pulling a small cart" or insufficient cooling.

- High energy consumption: Frequent starts and stops lead to energy waste.

Ii. Variable Frequency Drive (VFD)

Applicable scenarios

Variable frequency technology achieves continuous energy regulation by adjusting the speed of the compressor, and is suitable for scenarios that require high-precision temperature control, energy conservation, and extended equipment lifespan. Variable frequency regulation can achieve dynamic matching of cooling capacity and load, reduce energy waste and improve system efficiency.

Advantages

- Remarkable energy-saving effect: Variable frequency regulation is one of the regulation methods with the lowest energy consumption and high temperature control accuracy.

- Extend equipment lifespan: Reduce frequent starts and stops, and lower mechanical wear.

- Strong adaptability: Suitable for working conditions with large load variations, such as cold storage, industrial chillers, etc.

Applicable scenarios

- Large water chillers and industrial water chillers: Frequency conversion regulation can significantly improve energy efficiency, especially suitable for scenarios with large load fluctuations.

- Precise temperature control requirements: such as laboratory chillers, cooling of precision instruments, etc.

Iii. Compressor Unloading Control (Unloading control)

Applicable scenarios

The energy can be regulated in stages by adjusting the intake position of the compressor cylinder or the position of the slide valve. It is suitable for multi-compressor systems or scenarios that require phased regulation.

Advantages

- Flexible adjustment: The compressor output can be flexibly adjusted according to load changes, avoiding frequent starts and stops.

- Excellent energy-saving effect: Precise energy control is achieved through unloading or loading.

Disadvantage

- Complex structure: It requires multi-level control and regulation devices, resulting in a relatively high cost.

- Limited application scope: Mainly applicable to systems with multiple compressors.

Iv. Hybrid Control Strategy

In practical applications, a combination of multiple control strategies is often adopted to achieve the best energy efficiency and control effect. For example:

- Frequency conversion + unloading control: By integrating frequency conversion regulation and unloading control, more precise energy regulation is achieved.

- Intelligent control algorithm: Through PLC or intelligent control system, the compressor's start and stop, frequency conversion or unloading state is automatically adjusted according to load changes to achieve optimal operation.

V. Selection Suggestions

1. Small-scale equipment or small load variation: Intermittent operation (ON/OFF) control is adopted, which is simple and easy to implement with low cost.

2. Medium load or energy conservation required: Adopt variable frequency regulation to enhance energy efficiency and temperature control accuracy.

3. Large-scale systems or complex working conditions: Adopt frequency conversion + unloading control or intelligent control to achieve more precise energy regulation.

Vi. Summary

When choosing the start-stop control or frequency conversion regulation of the compressor of low temperature chiller according to the load fluctuation, it is necessary to comprehensively consider the system load characteristics, energy efficiency requirements, equipment life and control accuracy. Variable frequency regulation is currently the most recommended energy-saving and efficient control method, especially suitable for heavy-load and precise temperature control scenarios. For small or simple systems, intermittent operation control can still serve as a low-cost solution.