SIEMENS IEC

The trip curve determines the instantaneous tripping threshold relative to the rated current. A-curve devices trip at 2 to 3 times the rated current, making them suitable for resistive loads or circuits with low inrush currents. D-curve devices trip at 10 to 20 times the rated current, designed for loads with high inrush currents such as motors, transformers, and solenoid valves. For example, a 10 A D-curve protector (MPN 5SY42108) will tolerate a brief inrush of up to 200 A before tripping, whereas an A-curve protector of the same rating would trip at 20-30 A. Choose the curve based on the load characteristics to avoid nuisance tripping.

The 5SY4 series includes both UL1077 supplementary protectors and UL489 miniature circuit breakers, depending on the specific model. The products listed in the 3G Electric catalog (e.g., SKU 30XU80, MPN 5SY42038) are UL1077 supplementary protectors. UL1077 devices are intended for use as supplementary overcurrent protection within equipment, not as branch circuit protection. They are suitable for industrial control panels, HVAC equipment, and machinery where the upstream branch circuit protection is already provided. For branch circuit protection, use UL489-listed MCBs. Always verify the listing on the device label or datasheet.

For the 5SY4 series supplementary protectors, the screw-clamp terminals accept conductors up to 25 mm² (approximately 4 AWG) for current ratings above 32 A. For lower current ratings (e.g., 1.6 A to 25 A), the terminal capacity is typically up to 16 mm² (6 AWG). The clamping torque is specified as 2.0-2.5 Nm for most models. Always refer to the product datasheet for exact specifications, as terminal capacity may vary by current rating. The terminals are designed for copper conductors only.

Yes, the 5SY4 series supplementary protectors are rated for DC operation up to 72 V DC. This is indicated in the specifications for models such as the 5SY42038 (3 A, D-curve) and 5SY42108 (10 A, D-curve). The DC rating applies to both 2-pole and 4-pole configurations. For DC applications, ensure the polarity is observed and the device is used within its rated voltage and current limits. The interrupting capacity at DC may differ from the AC rating; consult the manufacturer's documentation for specific DC performance data.

The interrupting capacity for the 5SY4 series supplementary protectors is 10 kA at 400 V AC. This is consistent across the models listed, including the 3 A (5SY42038), 10 A (5SY42108), and 50 A (5SY42508) variants. The DC interrupting capacity is typically lower; for example, at 72 V DC, the rating may be 10 kA as well, but always verify with the specific product datasheet. This rating ensures the device can safely interrupt fault currents up to 10,000 amperes under short-circuit conditions.

The Siemens 5SY4 series supplementary protectors are designed to operate within an ambient temperature range of -25°C to +55°C. This range covers typical industrial environments, including unheated enclosures and control panels. Storage temperature range is -40°C to +70°C. The devices are rated for pollution degree 2, meaning they are suitable for environments with only non-conductive pollution, such as typical control rooms and light industrial settings. For applications outside this range, consult Siemens for derating or alternative products.