ylikuormituskäynnistin

Ylikuormituskäynnistin, sometimes referred to as an overload relay or thermal overload relay, is a crucial safety device in electrical systems. Its primary function is to protect electric motors from damage caused by overcurrent conditions. Overcurrent can arise from various issues, such as a motor becoming jammed, an excessive load being applied, or a phase imbalance in a three-phase system. These situations draw more current than the motor is designed to handle, leading to overheating.

The ylikuormituskäynnistin works by monitoring the current flowing through the motor. Most commonly, it utilizes a bimetallic strip that heats up as current passes through it. If the current exceeds a safe level for a prolonged period, the bimetallic strip bends sufficiently to activate a mechanism that trips open a set of contacts. These contacts are typically wired in series with the motor's control circuit, interrupting the power supply to the motor and preventing it from sustaining damage due to overheating.

Once tripped, the ylikuormituskäynnistin usually needs to be manually reset, either by pressing a button or turning a dial. This manual reset is a safety feature, ensuring that the cause of the overload is identified and rectified before the motor is restarted. Some models may offer automatic reset capabilities, but these are less common for critical motor protection applications. The trip setting of the ylikuormituskäynnistin is adjustable, allowing it to be calibrated to the specific full-load current rating of the motor it is protecting, ensuring effective and appropriate protection.