Technical data
Analog Input Control	4 - 20 mA
Approvals	UL
Load current up to	50 A
Load voltage up to	AC 480 V
Number of poles	1-pole
Width	22,5 mm, 45 mm, 90 mm
Type	BF 9250/0_2
Temperature monitoring
Variant
Auxiliary voltage	AC/DC 24 V
Contact equipping	without signal contact
Control input	DC 4 - 20 mA
Load current	AC 10 A
Load voltage	AC 230 - 480 V
Semiconductor output	1-pole
Approvals and Markings	UL-listed C/US
Variant	Self optimising, to achieve as short as possible control periods, suitable for infrared lamps

The Dold semiconductor contactor BF9250.91/042 is a 1-pole industrial switching device with an analog control input for precise temperature control in industrial applications. It is operated with an auxiliary voltage of AC/DC 24 V and features a control input in the range DC 4–20 mA, used for pulse packet control of heating elements. The device is designed for load voltages of AC 230 to 480 V and a load current of AC 10 A, and is particularly suitable for controlling infrared lamps, as it enables self-optimized pulse distribution with minimized cycle times. The width is 22.5 mm, making it suitable for compact mounting on DIN rail.

Applications
This device is designed for use in industrial heating systems where precise and disturbance-free temperature control is required. It is frequently used in process controls, such as in the packaging industry, food processing, or plastic processing. The zero-voltage switching mode ensures noiseless and disturbance-free switching, which is especially important for sensitive installations. The pulse packet control enables precise adjustment of heating power according to the specific process requirements.

Functions and equipment in detail
The control input can be operated either as a current signal (DC 4–20 mA) or as a voltage signal (DC 0–10 V). The input signals can be operated inverted, enabling flexible integration into existing control systems. The device features an LED indicator that visually signals the operating status: green LED for auxiliary voltage, yellow LED for output status, and red LED for alarms. In case of a synchronization error, a control input fault, or overheating of the power semiconductor, the red LED lights up, with the overheating alarm being latched and requiring a brief interruption of the supply voltage to reset.

Technology explained simply
The semiconductor contactor operates as a zero-voltage switch, meaning the switching action occurs precisely at the zero crossing of the alternating voltage. This avoids the generation of interference voltages and electrical sparks, increasing component lifespan and preserving power quality. The varistor protection circuit protects the device against transient overvoltages, which may occur due to switching operations in the network. The temperature protection function of the power semiconductor prevents overheating and shuts off the device when a critical temperature is reached, avoiding damage.

Compatibility and accessories
The device is compliant with IEC/EN 60947-4-2 and IEC/EN 60947-4-3 and carries the UL-listed C/US approval, enabling its use in the USA and Canada. It is designed for ohmic loads, such as heating strips, heating ovens, or infrared lamps. The load voltage up to AC 480 V and the load current up to AC 50 A allow broad application across various voltage levels. The width of 22.5 mm corresponds to the standard size for 10 A variants and enables compact mounting in enclosures.

Mounting and installation
The device is snap-on mounted on DIN rail, enabling quick and secure installation in enclosures. Recommended clearances to the environment are 20 mm above and below and 10 mm to the right and left, to ensure sufficient cooling. The operating temperature ranges from 0 to 40 °C, with current derating occurring above 40 °C to limit thermal stress.

Advantages in operation
The pulse packet control enables very precise and responsive temperature control, improving process quality. The noiseless switching function reduces mechanical stress and environmental disturbance. The integrated LED indicator provides quick visual diagnosis of operating states and faults, simplifying maintenance and troubleshooting. The self-optimization of pulse distribution ensures shorter cycle times and faster adaptation to load changes, which is particularly beneficial in dynamic processes.