4  FM quick reads on UPS

1. UPS can protect power supply

Today's tip is to consider online uninterruptible power supplies (UPS) to protect data centers. Generators can offer long-term protection from interrupted service, but only a UPS can protect against many common faults in power systems.

An online UPS has three components: a charger/rectifier, storage batteries, and a power inverter. Incoming alternating current from the utility enters the charger/rectifier, which converts it to direct current. This direct current charges the batteries and supplies power to the inverter, which converts the direct current back to alternating current. In systems that provide power for loads in extended outages, a generator typically is connected to the batteries.

The UPS supplies power to the loads continuously, no matter what happens to the utility power. But taking alternating current from the utility, converting it to direct current and back to alternating current also eliminates most power disturbances, including noise, transients, and voltage fluctuations.

Passive-standby systems provide the lowest level of protection and are the least expensive of the three. These off-line systems monitor incoming power and switch to a battery source when an interruption occurs. This transfer takes place in milliseconds and is acceptable for some computer-based applications. But the loss of power during the transfer can disrupt some sensitive electronic equipment. These UPS also do not filter power-line noise or voltage spikes or sags, so their use is limited largely to desktops or similar systems not performing critical tasks.

Line-interactive systems insert a transformer or an inductor between the power source and the connected equipment, and a bank of batteries helps condition and filter incoming power. The systems offer more protection than passive-standby but do not offer enough protection for mission-critical operations, such as data centers.

Double-conversion systems are true online UPS. They eliminate the momentary loss of power found in the other two types of UPS by using a bank of batteries connected to the direct-current part of the system. They fully isolate protected equipment from the power source, thereby eliminating most power disturbances. Run times range from 15 minutes to as long as the generator's fuel lasts.

2.  UPS: A Maintenance Checklist

This is Chris Matt, Managing Editor of Print & E-Media with Maintenance Solutions magazine. Today's tip is a checklist for uninterruptible power supply (UPS) maintenance.

The lifespan of UPS batteries is typically three-five years, depending on conditions and maintenance. At that time, technicians must replace them to ensure the unit operates properly. Keeping tabs on indicators of problems can ensure uninterrupted service to the equipment and facility operations, and, in many cases, a healthier bottom line.

Fortunately, many newer UPS have advanced monitoring systems that provide system status for such items as system voltage, battery back-up time, and battery test schedule.

Many systems can remotely alert technicians if a problem occurs. This information can be especially helpful if technicians monitor the facility remotely. Technicians also must test physical equipment quarterly, semi-annually, or annually using a specific checklist of items to cover. The schedule should include:

• conducting visual inspections for wear and deterioration of battery and insulation components
• cleaning and vacuuming the enclosure
• monitoring the enclosure's temperature and humidity
• performing thermal heat scans, which can indicate hot spots that often are the first sign of component failure
• testing other electrical-system components, such as transfer switches, circuit breakers, and maintenance bypasses.

3.  Power Management: Common UPS Technology

This is Chris Matt, Managing Editor of Print & E-Media with Maintenance Solutions magazine. Today's tip is understanding four common uninterruptible power supplies (UPS).

When the time comes to change a UPS, managers have a number of options from which to choose, and the choice will depend on the facility's current equipment and future needs. Common UPS technologies include:

Flywheel UPS. If managers use a UPS in conjunction with a generator system, the flywheel might be a good option. It packs enough inertia to carry the critical loads through a power outage for a short period — normally 10-20 seconds — until the generator has started, stabilized, and picked up the required loads.

True online UPS. This type of UPS — sometimes referred to as double conversion or double-conversion online — provides a high level of reliability for large servers, data centers, and large, sensitive equipment. Under normal operation, it runs continually off the battery via the inverter, and the line power runs the battery charger. For a true online UPS, there is no transfer time upon the loss of utility power.

Standby online hybrid. This UPS — also sometimes referred to as double conversion on demand — is similar to a true online UPS but with higher energy efficiency. The significant difference is standby online hybrid UPS loads are served directly from utility power, as long as the power is within acceptable tolerances.

Line-interactive UPS. This UPS continually conditions and regulates alternating-current utility power to equipment via a power converter. If the utility power fails or falls outside the input range of the power converter, the UPS battery will support the loads via an inverter.

4.  Data Centers and HVAC Setpoints

I'm Brandon Lorenz, senior editor for Building Operating Management magazine. Today's tip: Cooling in the data center.

When it comes to improving the efficiency of data centers, one of the first thing data center managers think of is airflow. And that makes sense because most data centers aren't the most airtight. But there are other opportunities for improvement too. The HVAC system and central plant is another logical place to look.

Consider an existing data center, for example. Periodically check the setpoints of the central plant to make sure they match the load of the data center, because the load often evolves over time. It's not out of the ordinary for the chiller plant to be set for the baseline UPS load and never adjusted, even as the load doubles as more servers are added to the data center.

Secondly, take a look at the way temperature sensors and CRAC units are situated. Move temperature sensors to the supply air outlet to better regulate the temperature of air delivered to the cold aisles. Doing so may allow you to raise the temperature of supply air, improving efficiency.


UPS , battery , generator , passive-standby , line-interactive , double-conversion

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