Ylikuormitussäätimiä

Ylikuormitussäätimiä, known in English as overload relays, are protective devices used in electrical systems to prevent damage to motors and other equipment caused by excessive current. They are designed to detect when the current drawn by a load exceeds a safe operating limit and to quickly disconnect the power supply. This prevents overheating and potential burnout of the motor windings or other components.

There are several common types of overload relays. Thermal overload relays are the most prevalent. They utilize a bimetallic strip that bends when heated by the current passing through it. If the current is too high for an extended period, the bending strip trips a mechanism that opens the circuit. Electronic overload relays offer more sophisticated protection. They use current transformers to measure the current and microprocessors to analyze it, allowing for adjustable trip points, faster response times, and features like phase loss detection. Magnetic overload relays, while less common for motor protection, react instantaneously to sudden short-circuit currents.

The primary function of an overload relay is to provide overcurrent protection for motor circuits. They are typically installed in series with the motor's power supply and are often used in conjunction with a contactor, which handles the main switching of power to the motor. When an overload condition is detected, the overload relay trips the contactor, interrupting the power flow to the motor. Proper sizing and selection of overload relays are crucial to ensure effective protection without nuisance tripping during normal operation. They are an essential component for ensuring the longevity and reliability of electrical machinery.