Uninterruptible Power Supplies- What Are Their Components?

EPO (Emergency Power Off), this feature on UPS systems can cause many problems to the smooth running of the power protection installation.

The primary reason for having this feature is to enable the UPS system to be ‘made safe’ in the event of an emergency. Operation of the Emergency Power Off will, with most uninterruptible power supplies, stop the inverter and rectifier (charger) and disconnect the battery. Due to the economics of size and cost, in a number of cases operation of the EPO circuit may just stop the inverter.

A typical example of a situation when there is a need to remove power to equipment in an emergency situation is in the case of fire. An un-interruptible power supply by its very name means that when the building is isolated it will continue to provide an output until the batteries are exhausted. The continued supply of power in these situations can lead to additional fires as cables are damaged by the original cause. The EPO in this situation is often connected to the fire alarm panel and will operate on the second and subsequent detection of fire within a defined area.

Puck under cabinet display lights experience difficulty creating an even field of illumination. If a puck light is installed in the center of the cabinet underside, it will create a bright circle of light called a “hot spot” immediately beneath itself. Also, by design, surface puck lights require exposed wiring and low voltage transformers that may be unsightly and appear as an afterthought. If sitting at tables, banquets or bar stools, one’s viewing angle changes and provides a clear view of these light sources. The only way to compensate for this is to install several of smaller puck lights in a series. Why do this if you can use a strip light products? In fact, with only rare exceptions, linear LED strip lights for under cabinet generally provide the best levels and distribution of light all around. Fluorescents will fit the bill in many respect, but in many instances will also create glare and seldom come with dimmable functionality. Furthermore, fluorescent strips are typically mounted near the back wall with the light thrown forward; putting too much illumination into a person’s eyes from a sitting position.

Static Switch : this circuit can be as simple as a relay or more commonly using thyristors, its purpose is to switch the load between the inverter and the utility mains supply. As has been previously mentioned the output of the inverter is in phase with the utility mains supply so that any switching between the two will be virtually seamless. This arrangement ensures that if the inverter experiences an overload situation, due to its extremely fast over-current detection circuits it will transfer the load to the more resilient mains supply. A typical example would be when a server rack is switched on, the inrush current, depending upon the size of your uninterruptible power supplies , could cause the transfer to the utility mains supply, and once switched on the load will transfer back to the inverter providing the inverter has sufficient capacity to support the load. Also a fault on the inverter will cause the load to be transferred, again virtually seamlessly; it would be unusual for any loss of load to occur during these conditions.

You must be very careful where the EPO is positioned, to avoid accidental or malicious use. Certainly each EPO needs to be monitored and covered y CCTV at the very least.

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