päällepoiskytkimistä

Päällepoiskytkimet, often translated as "overload relays" or "thermal overload devices," are crucial safety components in electrical systems. Their primary function is to protect electric motors and other electrical equipment from damage caused by overcurrent conditions, which can arise from various faults such as mechanical overload, phase loss, or short circuits.

These devices operate by sensing the current flowing through the protected equipment. They typically utilize bimetallic strips or thermal elements that heat up in response to excessive current. As the bimetallic strip heats, it bends, and this mechanical movement is used to trigger a mechanism that opens the power circuit, thereby interrupting the flow of electricity and stopping the motor. This prevents the motor windings from overheating and sustaining permanent damage.

Päällepoiskytkimet are designed to have a time-delay characteristic, meaning they don't trip instantly on brief, harmless current surges that are common during motor startup. However, they will respond to sustained overcurrents that indicate a problem. Many päällepoiskytkimet are adjustable, allowing the user to set the precise trip current according to the motor's full-load amperage rating. They are often integrated with motor starters or circuit breakers, or they can be installed as standalone units. Proper selection and setting of päällepoiskytkimet are essential for ensuring the longevity and reliability of electrical equipment.