UPS types
There is a lot of confusion in the market about the different betweenUPS types and its characteristics.
In this article each one is reviewed, the practical applications are discussed, and the advantages and disadvantages are listed. With this information, a good decision can be made about the most appropriate UPS for each need. The variety in UPS types and their attributes often cause confusion in the data center industry. For example, it is believed that there are only two types of UPS systems, UPS standby, and UPS online. These two commonly used terms do not correctly describe many of the available UPS systems. Many of the problems with UPS systems are solved when the difference between UPS types are properly identified.
The most common UPS types are the following:
- Standby
- Line Interactive
- Standby on-line hybrid
- Standby-Ferro
- Double Conversion On-Line Delta Conversion On-Line
- Delta Conversion On-Line
UPS Standby
UPS Standby is the most common type used for personal computers. The primary source. When that happens, the transfer switch must operate to switch the load to the inverter battery source/backup power. This transfer of electrical power to the battery power (called commutation time) is usually in the order of 5 milliseconds, which is imperceptible for most home electronic equipment.
Line Interactive
The interactive UPS is the most common design used for small business, Web and departmental servers. In this design, the battery AC power converter (inverter) is always connected to the output of the UPS. It always provides normal AC power to charge the battery.
Voltage regulation is an important feature when there are low voltage conditions, otherwise, the UPS would transfer the problem to the battery and eventually reach the load. This frequent use of the battery can cause premature battery failure. However, the inverter can also be designed in such a way that its fault still allows the flow of power from the AC input to the output.
The interactive line UPS is an improved design that is commonly used in units for home and professional use, available in sizes up to 3kVA or less. It is superior to standby UPS, but still has a transfer time, and therefore does not provide as good a protection as the online UPS, which we will see later.
Standby on-line hybrid
The standby UPS on-line hybrid is the topology used for many UPSs of around 10kVA that are labeled “online”. The DC to DC conversion of the battery is turned on when an AC power failure is detected, as in a Standby UPS. Due to the capacitors in the DC combiner, the standby UPS on-line hybrid does not present any transfer time during an AC power failure.
Standby-Ferro
This design depends on a special saturation transformer that has three windings. The primary power path is AC input, through a transfer switch, then through the transformer, and to the output. In the case of a power cut, the transfer switch opens, and the inverter picks up the output load.
In the Standby-Ferro design, the inverter is in standby mode and is activated when the input power fails and the transfer switch is opened.
The insulation of the AC power transients provided by the Ferro transformer is as good or better than any available filter. But the Ferro transformer itself creates a lot of distortion and output voltage transients, which can be worse than a poor AC connection.
Although it is a standby UPS by design, the Standby-Ferro generates a large amount of heat because the Ferro-resonant transformer is inherently inefficient. These transformers are also large in relation to regular isolation transformers; so Standby-Ferro UPSs are generally quite large and heavy.
Standby-Ferro son UPSs are often represented as On-Line units, although they have a transfer switch, the inverter operates in Standby mode.
The Double Conversion On-Line UPS
The block diagram of the online double conversion UPS, is the same as the standby mode, with the exception that the primary power path is the inverter instead of the source Main AC.
In addition, the input power of the large battery charger is often non-linear and can interfere with the construction of power cabling or cause problems with the generators (power plants). In the double line design conversion, the failure of the AC input does not cause the transfer switch to activate, because the AC input is not the primary source, but rather is the backup source. Therefore, during an AC power failure at the input, the UPS will operate online which will result in a short transfer time.
Delta Conversion On-Line
The Delta UPS online conversion always has the inverter supplying the charging voltage. However, the additional Delta converter also contributes to the output power of the inverter. In conditions of AC failure or disturbances, this design exhibits identical behavior to double in-line conversion.