Why would I need a protection module for a 24Vdc circuit?

A protection module fulfills two basic functions. First it distributes the current of a large power source to four lower current output channels and therefore allows for smaller wires to be used. The second function is to permit only so much current on the outputs that the input voltage of this unit (which corresponds to the output voltage of the power supply) does not fall below 21V. This ensures a reliable supply voltage for sensitive equipment, such as PLCs, controls or sensors, when they are connected directly to the same power supply as the PISA protection module. The protection module has one 24V input and four output channels to which the current is distributed. Each output channel is equipped with a redundant over-current protection, which avoids that wires will be overloaded. All four output channels will shutdown simultaneously, if the current of one individual channel or the maximum allowed current for the protection module is exceeded. A safeguard circuit in the input stage of the PISA module works like a valve. It permits only so much current that the input voltage does not drop below 21V. In case the input voltage would fall below this value (e.g. due to overloads, too small of a power supply or high inrush currents such as from starting a motor), all four output channels will be actively current limited and will shutdown after a certain period of time. A typical wiring configuration is shown below. All sensitive loads are connected directly to the power supply. If needed, these load circuits can be protected with standard circuit breakers or fuses. Loads which are less sensitive to voltage dips or interruptions or which are the source of the voltage drop themselves are connected to the output of the PISA protection module.