Überlastschutz

Überlastschutz refers to the protective measures in electrical systems that detect and respond to overload conditions—situations in which current, heating, or other stress exceeds safe limits. The main purpose is to prevent damage to conductors, insulation, motors and transformers, and to reduce the risk of fire or equipment failure. Overloads typically arise from continuous overcurrent during normal operation, faulty wiring, or start-up surges.

Function and principles: Overload protection relies on monitoring current or temperature. If current remains above the rated value for a specified period, a protective device trips, interrupting the circuit. Many devices combine thermal (time-delayed) and magnetic (instantaneous) protection to distinguish overload from short circuits.

Devices and implementations: Fuses provide simple, non-resettable protection by melting the conductor when overloaded. Circuit breakers provide resettable protection with thermal and magnetic elements for overload and short circuits. Thermal overload relays, often used with motor starters, monitor winding temperature or load current to protect motors from overheating. Electronic or microprocessor-based motor protection relays offer adjustable trip characteristics and can integrate with soft starters or variable-frequency drives, which themselves frequently include built-in overload protection.

Standards and usage: Überlastschutz is required in electrical installations and machinery to meet safety standards and ensure reliability. Typical considerations include setting appropriate trip thresholds, coordination with upstream protection, and regular testing.