MSR Series Surge Protective Devices (SPD)

MSR series Surge Protection Devices (SPDs) are manufactured while using multi-stage protection circuits. They are used to protect communication circuits, working with common industrial protocols. A gas-filled surge arrester is used as a rough protection in the circuits, while a transient voltage suppressor (TVS) or varistor, or a combination thereof, is used as the thin protection element. 

Such a solution allows to achieve a high diverting ability, a sufficiently low protection threshold (SPD operating voltage) and a high response speed. The current protection stages together with isolation elements can be placed in a single compact case mounted on a DIN rail, 18 or 36 mm wide, given the relatively low discharge currents values (when compared with power supply circuits). 

The current SPDs are connected in series in the signal circuit and data transmission circuits with various communication interfaces, including RS-485, RS-422, current loop, HART, Profibus, Fieldbus and others. Therefore, the protective circuit must take into account both the permissible impulse effects levels on the protected equipment as well as internal protected circuits and interfaces features, including rated current - from 0.1 A to 0.5 A, rated voltage - 6, 12, 24, 30 B and transmission speed - up to 10 Mbps. TVS diodes provide dissipation up to 1500 W or up to 3000 W of pulsed power, depending on the components being applied. 

There is a chance to connect both shielded and unshielded two-wire differential communication lines, with one or two signal wires pairs. It is also possible to ground the cable screen through a shunt capacitance.