Back-feed protection, in uninterruptible power supplies (UPS), goldshell Miners prevents the risk of electric shock from any electric current feeding back from the UPS output in the event of a mains supply failure. When mains fails and connected loads are protected by uninterruptible power supplies, a back-feed protection device prevents current from being passed back to the input terminals of the UPS from the inverter output.
This is extremely important for health and safety reasons because it enables a service engineer to work on the incoming supply side of the UPS without risk of receiving an electric shock.- not only to safeguard engineers but uninterruptible power supply protected loads too.The type of back-feed device employed is determined by the size of the uninterruptible power supply.
A example of what could happen, in the event of a mains power failure, is that a bypass supply thyristor, which has short-circuited causing the output from the inverter to be passed through to the input terminals via the faulty component. It is something that must be prevented at all costs
Even when the input supply has been switched off, via an isolator, there is potential for it to happen, hence the need for back-feed protection.
Plug-in Uninterruptible Power Supplies Back-feed protection for a single-phase uninterruptible power supply, up to 16A, needs to provide protection for both live and neutral input conductors using a specified air gap. The air gap is usually provided by means of a relay that opens when mains power supply fails.
For plug-in power supplies, if a fault occurs when the user disconnects it from the mains power supply (by simply unplugging it from the wall socket), the back-feed relay should prevent the exposed pins from becoming live. It should also remove any possibility of the user receiving an electric shock. UPS systems over 16A are hardwired (normally) and utilise one of two different approaches: mechanical or electronic.