An overload protector, designed according to the practical requirements of the electrical control industry, serves as a protective device for power circuits. It utilizes microcontroller design technology, offering comprehensive functionality, reliable operation, strong immunity to interference, and suitability for challenging working environments. This protector effectively safeguards electrical systems, squirrel-cage motors, and wound-rotor motors from overcurrents, short circuits, phase loss, phase imbalance, incorrect phase sequences, and excessive startup currents.

The fundamental working principle of an overload protector in a chiller (cold water machine) typically involves the use of a bimetallic thermal protection device. These devices are commonly employed within refrigeration compressor circuits. The protection mechanism consists of a combination of a heating wire, a bimetallic strip, and two static contacts, forming a complete power circuit connected to the refrigeration compressor.

Here’s how it works:

1. When the current in the system’s power circuit unexpectedly increases, the heating wire generates significant heat.
2. The heated bimetallic strip bends in the opposite direction due to the heat, causing the static contacts to open. This action interrupts the power supply to the compressor.
3. Even if the operating current remains normal, the overload protector will still respond if the external temperature of the refrigeration compressor or motor becomes excessively high.
4. Importantly, this protection mechanism is self-resetting, making it convenient for practical use.

The primary functions of a chiller overload protector include:

• Overcurrent Protection: The bimetallic strip responds to excessive current, disconnecting the power supply to prevent overheating.
• Overtemperature Protection: If the compressor’s external temperature rises significantly, the overload protector acts to prevent damage.
• Dual Safeguard: It combines overcurrent and overtemperature protection.
• Installation Considerations:
  1. The sensitivity and accuracy of built-in overload protectors differ from external ones. Generally, built-in protectors require higher sensitivity and accuracy.
  2. In cases of refrigerant shortage or leaks in industrial chiller units, both types of overload protectors have limited effectiveness. Additional specialized protection for refrigerant shortages is advisable.
  3. Excessive refrigerant in industrial chillers also poses limitations for both types of overload protectors. Corresponding measures are necessary to prevent damage to the refrigeration compressor.
  4. High compression ratios weaken the protection function of overload protectors. Independent low-pressure protection measures are essential to ensure the safety of the refrigeration compressor.

In summary, overload protectors play a crucial role in maintaining the safe and reliable operation of refrigeration compressors and associated machinery. They are widely used in various industries, including mechanical, metallurgical, construction materials, and chemical sectors, to protect and monitor three-phase electric motors and other electrical equipment.