4 Kinds of Uninterruptible Power Supply (UPS) Design

UPSToday. - There are many Uninterruptible Power Supply (UPS) design in the world that developed to give best result to user. Minimum there are 4 kinds designs of Uninterruptible Power Supply (UPS) that used according Wikipedia. You also can read Uninterruptible Power Supply (UPS): Definition, Typically Used, and Technology.

Rotary Uninterruptible Power Supply (Source: screenshot of Green Data Center Design and Management)

4 kinds of Uninterruptible Power Supply (UPS) design as like Hybrid topology / double conversion on demand, Ferro-resonant, DC power, and Rotary. And here are the description of all UPS design as follow.

A. Hybrid topology / double conversion on demand

The first design of UPS is Hybrid topology / double conversion on demand. A hybrid (double conversion on demand) Uninterruptible Power Supply operates as an off-line/standby UPS when power conditions are within a certain preset window. This allows the Uninterruptible Power Supply to achieve very high efficiency ratings. When the power conditions fluctuate outside of the predefined windows, the UPS switches to online/double-conversion operation.

Proposed hybrid topology for an UPS with possible connection modes of supercapacitor  (Source: Screenshot of researchgate)

In double-conversion mode the Uninterruptible Power Supply can adjust for voltage variations without having to use battery power, can filter out line noise and control frequency. Examples of this hybrid/double conversion on demand UPS design are the HP R8000, HP R12000, HP RP12000/3 and the Eaton BladeUPS.

B. Ferro-resonant

The second design of UPS is Ferro-resonant. Ferro-resonant units operate in the same way as a standby Uninterruptible Power Supply unit; however, they are online with the exception that a ferro-resonant transformer is used to filter the output. This transformer is designed to hold energy long enough to cover the time between switching from line power to battery power and effectively eliminates the transfer time. Many ferro-resonant UPSs are 82–88% efficient (AC/DC-AC) and offer excellent isolation.

Block schematic of a ferroresonant standby UPS (Source: Screenshot of pcguide)

The transformer has three windings, one for ordinary mains power, the second for rectified battery power, and the third for output AC power to the load. This once was the dominant type of UPS and is limited to around the 150 kVA range. These units are still mainly used in some industrial settings (oil and gas, petrochemical, chemical, utility, and heavy industry markets) due to the robust nature of the Uninterruptible Power Supply. Many ferro-resonant UPSs utilizing controlled ferro technology may not interact with power-factor-correcting equipment.

Additional information for you that Ferro-resonant UPS also any called with a ferroresonant standby UPS that mean an improvement on the design of the standby UPS. As with a standby UPS, the primary power source is line power from the utility, and the secondary power source is the battery. The battery and inverter are still waiting "on standby" until needed. The big difference is that the standby UPS's transfer switch that selects between power sources has been replaced by a ferroresonant transformer.

C. DC Power

The third design of UPS is DC Power. A UPS designed for powering DC equipment is very similar to an online UPS, except that it does not need an output inverter. Also, if the Uninterruptible Power Supply's battery voltage is matched with the voltage the device needs, the device's power supply will not be needed either. Since one or more power conversion steps are eliminated, this increases efficiency and run time.

12V DC Power UPS Diagram (Source: Screenshot of electronics stackexchange)

Many systems used in telecommunications use an extra-low voltage "common battery" 48 V DC power, because it has less restrictive safety regulations, such as being installed in conduit and junction boxes. DC has typically been the dominant power source for telecommunications, and AC has typically been the dominant source for computers and servers.

There has been much experimentation with 48 V DC power for computer servers, in the hope of reducing the likelihood of failure and the cost of equipment. However, to supply the same amount of power, the current would be higher than an equivalent 115 V or 230 V circuit; greater current requires larger conductors, or more energy lost as heat. A laptop computer is a classic example of a PC with a DC Uninterruptible Power Supply built in.

High voltage DC (380 V) is finding use in some data center applications, and allows for small power conductors, but is subject to the more complex electrical code rules for safe containment of high voltages.

D. Rotary

The fourth design of UPS is Rotary. A rotary Uninterruptible Power Supply uses the inertia of a high-mass spinning flywheel (flywheel energy storage) to provide short-term ride-through in the event of power loss. The flywheel also acts as a buffer against power spikes and sags, since such short-term power events are not able to appreciably affect the rotational speed of the high-mass flywheel. It is also one of the oldest designs, predating vacuum tubes and integrated circuits.

It can be considered to be on line since it spins continuously under normal conditions. However, unlike a battery-based UPS, flywheel-based Uninterruptible Power Supply systems typically provide 10 to 20 seconds of protection before the flywheel has slowed and power output stops. It is traditionally used in conjunction with standby diesel generators, providing backup power only for the brief period of time the engine needs to start running and stabilize its output.

Rotary UPS Design (Source: Screenshot of Green Data Center Design and Management)

The rotary UPS is generally reserved for applications needing more than 10,000 W of protection, to justify the expense and benefit from the advantages rotary Uninterruptible Power Supply systems bring. A larger flywheel or multiple flywheels operating in parallel will increase the reserve running time or capacity.

Because the flywheels are a mechanical power source, it is not necessary to use an electric motor or generator as an intermediary between it and a diesel engine designed to provide emergency power. By using a transmission gearbox, the rotational inertia of the flywheel can be used to directly start up a diesel engine, and once running, the diesel engine can be used to directly spin the flywheel. Multiple flywheels can likewise be connected in parallel through mechanical countershafts, without the need for separate motors and generators for each flywheel.

They are normally designed to provide very high current output compared to a purely electronic Uninterruptible Power Supply, and are better able to provide inrush current for inductive loads such as motor startup or compressor loads, as well as medical MRI and cath lab equipment. It is also able to tolerate short-circuit conditions up to 17 times larger than an electronic UPS, permitting one device to blow a fuse and fail while other devices still continue to be powered from the rotary UPS.

Its life cycle is usually far greater than a purely electronic Uninterruptible Power Supply, up to 30 years or more. But they do require periodic downtime for mechanical maintenance, such as ball bearing replacement. In larger systems redundancy of the system ensures the availability of processes during this maintenance. Battery-based designs do not require downtime if the batteries can be hot-swapped, which is usually the case for larger units. Newer rotary units use technologies such as magnetic bearings and air-evacuated enclosures to increase standby efficiency and reduce maintenance to very low levels.

According Green Data Center Design and Management blog describe that the advantages of Rotary UPS as follow.

1. Most energy efficient UPS/CPS system
2. Use of stored kinetic energy
3. No batteries required, that means no chemical waste!
4. Save energy for battery room's ventilation and cooling 
5. Lowest Total Cost of Ownership (TCO)
6. Highest power factor
7. No conditioned battery room required, that means saving space
8. Long life time
9. Efficiency about 96%

Typically, the high-mass flywheel is used in conjunction with a motor-generator system. These units can be configured as:

1. A motor driving a mechanically connected generator,
2. A combined synchronous motor and generator wound in alternating slots of a single rotor and stator,
3. A hybrid rotary Uninterruptible Power Supply, designed similar to an online UPS, except that it uses the flywheel in place of batteries. The rectifier drives a motor to spin the flywheel, while a generator uses the flywheel to power the inverter.

In case No. 3 the motor generator can be synchronous/synchronous or induction/synchronous. The motor side of the unit in case Nos. 2 and 3 can be driven directly by an AC power source (typically when in inverter bypass), a 6-step double-conversion motor drive, or a 6-pulse inverter. Case No. 1 uses an integrated flywheel as a short-term energy source instead of batteries to allow time for external, electrically coupled gensets to start and be brought online. Case Nos. 2 and 3 can use batteries or a free-standing electrically coupled flywheel as the short-term energy source.

So, from 4 Kinds of Uninterruptible Power Supply (UPS) design that describe above, we think you can different all and know what kinds of Uninterruptible Power Supply (UPS) design that you find in your live like using in computer system.

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