Considerations In choosing a UPS

Uninterruptible Power Supplies employ several different technologies. In selecting the best UPS for each application it is important to understand the basic differences in these technologies. Important factors in this decision include, importance of data, avoidance of downtime, power environment, and backup power generation. These are important for the following reasons.

• Importance of data: The more critical the data, the more important it is to protect it with a top quality system. Many times data cannot be recreated accurately without extensive reconstruction at a corporate level. This can take large amounts of time and money along with loss of business. In these circumstances it is inappropriate to use an inferior product to protect critical systems.
  
• Avoidance of downtime: Many companies today operate 7 days a week 24 hours a day. In these circumstances there is no available time for maintenance or equipment failure and due to the importance of the data, the company can not be exposed to potential power problems. In these situations a redundant system is advisable. With new power array systems this becomes easier and less costly.
  
• Power Environment: In poor power environments high quality UPS’s are required to avoid the constant switching of the UPS to battery. This constant switching can lead to quicker battery run down. In these circumstances an on line or ferroresonant unit is advised.
  
• Generator backup: When generators are involved, there may be more voltage problems. As in poor power environments the same recommendations apply.

Technologies:

• Standby (Off-line): These units filter normal power and the UPS switches to battery any time there is a power problem. These units are inexpensive and work well in supporting workstations. They are unsuitable in industrial or generator environments.
  
• Line-interactive: In a line interactive system the unit goes to inverter in periods of prolonged outage, but also uses boost and fade in order to regulate periods in which less than 12% frequency variations occur. These units give good performance at a low cost under 2.2 KVA and are effective in protecting departmental servers.
  
• On-line (double conversions): In these units all power is converted from AC to DC and then back to AC. This insures constant power quality. These units are more costly in smaller systems and are less efficient than other systems but work extremely well in power conditioning. They require larger generators to run, and can create high harmonics. They have lower power factors (approximately .8) than some other systems.
  
• Ferroresonance: A transformer design in which the transformer contains two separate magnetic paths with limited couplings between them. The output contains a resonating tank circuit that draws power from the primary to replace power delivered to the load.
  
• Single conversion: Highly efficient (97%) Three-Phase units providing a power factor of approximately 1. This gives more load capacity in many installations where new power corrected loads are present. Works well with generators as long as no large cycling loads are present.
  
• Delta Conversion: The newest technology with some extremely attractive advantages over other technologies. These include:
  A Unique internal powerfactor control which provides a powerfactor of approximately 1.

  
  This technology makes an external phase compensation unit unnecessary.

  High efficiency (96.5%) saves hundreds to thousands of dollars a month in utilities cost in most sites.

  Low Total Harmonic Distortion (THD) levels of less than 5 percent eliminate the need for costly Harmonic Filters.

  These units are Generator friendly, allowing for generator over-sizing as low as 1.3 times the UPS rating.

Definitions:

Power Problems and terms

Blackouts: The complete lose of utility power. These can cause system crashes, lost data, or corrupt data.

Brownouts: Sustained low voltage situations caused by overloads or excess demand. These can cause system crashes, overheating, damage, or operating errors.

Harmonics: Harmonics are power levels that are multipliers of your base frequency. There are positive, negative, and zero sequence harmonics that create magnetic fields rotating in the same rotation, opposite rotation or no rotating field. These can cause inaccuracy in metered measurements and can cause overheating of transformers, burned out diodes, reduced efficiency, and reduced equipment life.

Noise: Also known as harmonics, electromagnetic interference ( E M I ) and radio interference ( R F I ). Created by neighboring office equipment or machinery on the same power line. Can corrupt data and cause "glitches".

Over-voltage: Continuous voltage above normal caused by wiring faults or faulty regulation systems. This can cause overheating, component stress, damage, or corrupt data.

Power Factor: This is the ratio between KVA and kW necessary to run equipment. With most new computer equipment it is ~1. Traditional double conversion UPS normally operate with ~.8 power factor. In this situation one must look at the kW rating of the load or if the Power Factor is over .8 the unit can be overloaded at its KVA rating. This also reduces the efficiency of the equipment and with deregulation of power, there has been a move to penalize electric customers for low Power Factors.

Sine wave Power: Electrical power that has no problems that can cause damage to equipment. These include voltage Fluctuations, sags, swells, transients, steady-stage distortions or Harmonics.

Surge: Temporary over-voltage conditions that can be caused by startup of large loads. These can cause operating errors, system shutdowns, or component stress.

Spikes: Short duration sudden voltage jumps that can be caused by lightning or static discharges. These can cause operating errors, system shutdown, or corrupt data.

Transient Surges: Voltage Spikes caused by Lightning, Switching equipment, inductive loads, and Electro-Magnetic Interference. Large surges or multiple low level surges can burn out equipment or reduce its life expectancy.

Technology

Check-ups software: Best Power software for controlling UPS systems, also allows for SNMP management.

Hot swappable: The ability to change components without interrupting the load.

IGBT: Isolated Gate Bi-polar Transistors allow for the switching of large amounts of current with a small signal. These enable units to rapidly control the UPS and improve efficiency of the unit.

Isolated Redundant: The use of a second unit to act as backup. By doing this one can still maintain complete protection if a unit fails or preventative maintenance is required. The difference between this and parallel coverage is that with isolated redundant the additional unit is on standby and picks up the load only when required. The advantage of this type of system is that the units do not have to be identical. The units must be able to take a 100% step load which APC and MGE products can do.

Parallel: The use of more that one identical unit to share a load. This provides duplicate coverage of the load so that if one UPS unit fails or must have preventative maintenance the load is still completely protected.

Powerchute: APC’s software system for control and monitoring of UPS systems. Allow for multiple systems control through either SNMP or share-ups systems and allows for receptacle control using the Masterswitch units.

Redundancy: The providing of additional units over the load required. In this method you can still run on fully protected power when a unit is inoperable until the unit is fixed or replaced.

Solution-Pac: MGE’s Software system for controlling and monitoring UPS systems. This system allows for such features as receptacle shutdown in the case of ESV+ or Ellipse 1200 and also allows for SNMP and TCP/IP control.

SNMP: Simple Network Management Protocol allows for the use of networks to remotely monitor and control your UPS.

VA/KVA: The amperage required for a unit multiplied by the voltage. In Three Phase products this is amps x voltage x 1.73. KVA is VA x 1000.

For larger applications please email sales@steadypower.com