Hot swap power supply technology is not a new feature. First developed in the telecommunications industry over 40 years ago, hot swap power supplies have continued to evolve, keeping pace with modern technological advances in circuitry and power supply development. A hot swap power supply does not require interaction with your system before it is remove or replaced, meaning that the system can remain active while individual supplies are changed or swapped. This makes it easy to remove a failed power supply without interrupting the system, making them convenient particularly if a shutdown and restart of an entire system causes major inconvenience to a series of users.
Hot swap power supplies really come into their own on systems where a shutdown is not an option, such as in high tech computer networks or even medical equipment. Any failure of a power supply should not bring down a high-availability system – the system needs to continue functioning even if performance is reduced for a short period of time. Most hot swap power supplies overcome this problem by incorporating redundancy, meaning that if a supply within the system does fail it automatically switches over to a secondary supply to continue operating. The failed supply can then be removed and replaced without having to turn the entire system off.
When hot swapping first developed, the typical practice was to distribute a negative high voltage of –48V. This was done to guard against the potential for ionic corrosion associated with positive power when it is exposed to the elements. Since then, technology has moved on and new industry standards such as Power over Ethernet (PoE), the PCI standard and others have replaced this system. The PoE standard uses +48V power while PCI dictates +12V. Additionally, several other types of networking systems distribute power at voltage levels between +24V to +42V power.
Demand for hot swap technology in systems with high positive voltage power is growing, particularly in storage area networks (SANs), high availability servers base on the PCI bus, networking equipment with PoE and Internet switching systems. The latest developments are in mid-plane hot swapping. Mid-plane hot swapping takes positive or negative power at a high voltage of around 40V and makes use of a layered system to distribute power at the voltage and current needed throughout the network. The 40V supply is distributed via 12V supplies at a secondary level, which provides a distinct advantage in that a high voltage source can be trickled out through a series of inexpensive power supplies at the various points within the network. At each of these nodes hot swap technology can be incorporated, enabling one node to be taken offline and replaced should it fail without impacting the others. In particularly busy networks that require constant uplinks to a central power supply, this simple yet effective system gets rid of the 'fairy lights' scenario where one bulb failing causes all the others to fail as well. Hot swap power supplies can be thought of as the modern variation of fairy lights, where one bulb can be replaced without having to cut the power to all the others first.
Hot swap power supplies are the most convenient method of ensuring constant power supplies to a network of nodes with minimal impact should one node power supply fail. They are becoming the industry standard for any multiple application, making maintenance easy and far cheaper and drastically reducing down-time for organisations that rely on network technology.
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