Addressing one of the pitfalls of
Power Distribution in Modern Security Systems
The concept of providing multiple independent short circuit protected outputs on security power supplies is certainly not a recent innovation (Tactical has been offering this option on its products since 1997). The aim of distributed output systems is to ensure that if a short circuit or other major over-current situation (such as a faulty camera or deliberate vandalism) occurs on one output, it should not impact overall system operation or the functionality of devices connected to the other outputs. This is typically accomplished by using either a conventional glass fuse or polyswitch on each circuit run - there are pros & cons for using either device (such as temperature sensitivity and over current trip lagging).
Notwithstanding their individual strengths and weaknesses, the use of both fuses and polyswitches for distributed DC power applications can still be problematic, particularly when used with high in-rush current devices such as heavy duty electronic locks and PTZ cameras with environmental housings or long range IR illuminators. In such cases it is necessary to configure each output with a fuse or polyswitch with a rating high enough to provide the required start-up / in-rush current (often more than 400% greater than the manufacturers’ stated maximum running current for the connected device) without tripping. In doing so, it is common to have a situation where the system starts and operates correctly, but when a short circuit (or other high current event such as a device failure) occurs, the entire power supply shuts down before the individual over current protection (fuse or polyswitch) trips - resulting in every device connected to the power supply failing. This situation can be minimised by conservative selection of the main power supply (ensuring that the power supply has adequate additional current available to trip circuit specific over-current protection in addition to providing for running load of the connected devices) and careful selection of the value of fuses or polyswitches. Unfortunately, these calculations are quite often either not performed or are not correctly implemented - and worse still this is generally not discovered until an operational event occurs, leading to the primary power supply (and therefore all devices connected to it) shutting down.
Whilst this situation is certainly not unknown, it is generally not well understood and until recently, not easily addressed. After considerable research and development, Tactical have confronted the problem and have provided an innovative solution: Active Electronic Over-current Protection (AEOP) for each individual output (this is in addition to conventional over-current protection of the main power supply). Featured in newly released RPS24-DC Series models (designed for high security / high reliability applications such as detention centres and gaols), AEOP is accurately configured for each output, yielding a robust operational solution previously unavailable to the industry. AEOP will be rolled out as an option for other high-end Tactical DC models over the coming months as we expect this to become a popular requirement for high security / extreme reliability installations.
The operational advantages offered by this technology are so great that patents have been sought - complementing patents & patents pending already awarded to Tactical for innovations utilised in our range of high-end security products.