Classification and Types of UPS – Part Six

 

In the previous article “Classification and Types of UPS – Part One”, we stated that UPS is classified according to:

1. Voltage range,
2. No. of phases,
3. Mobility,
4. Technological design,
5. Physical Size/capacity,
6. Form factor/ configurations,
7. Topology,
8. Distribution Architecture,
9. Use of transformers.

 

We already explained the first seven classifications in the Previous articles (see table in the end of Article).

Today, we will continue explaining other Classification and Types of UPS.

 

Eighth: According to UPS Distribution Architecture

 

 

Understanding the UPS architecture is important as it has a direct influence on the available power to the protected devices. Many UPS Distribution Architectures divided according to the following Architecture forms:   Centralized Vs Decentralized UPS Systems, Conventional (Monolithic) Vs Modular UPS System.

 

First: Centralized Vs Decentralized UPS Systems

 

 

UPS backup power strategies are deployed in three main Architecture forms:   1- Centralized UPS Configuration, 2- Distributed (Decentralized) UPS Configuration, 2.1 Distributed UPS-Zonewise Configuration 3- Hybrid UPS Configuration.   From a technical standpoint they serve the same purpose, namely, to keep power flowing, particularly during adverse conditions (i.e., surges, brownouts, fluctuations, total power outages, frequency differences and other power issues). While they may serve the same purpose, they fulfill it in different ways. These solutions have advantages and disadvantages, depending on the short- and long-term needs of an organization.

 

 

1- Centralized UPS Configuration   It is a system where the UPS is installed in a centralized location like electrical panel room (see Fig.1), and then the power is distributed across the facility to support the critical loads generally of larger capacity. The capacity is decided based on the load level, future expansion plan and the redundancy levels required.   Fig.1: Centralized UPS Configuration

 

 

2- Distributed (Decentralized) UPS Configuration   It Is a system where a dedicated UPS is installed near to the loads like a rack mount UPS mounted on the server rack for server’s applications or 600 VA /1KVA UPS for desktop computers (see Fig.2)   Fig.2: Distributed (Decentralized) UPS Configuration

 

 

2.1 Distributed UPS-Zonewise Configuration   The distributed system can also be zonewise like floorwise or applicationwise ( see Fig.3) which can be based on medium range of UPS System (between 10 - 120KVA), if a UPS fails during a power outage, the impact is limited to the zone that device supports.   Fig.3: Distributed UPS-Zonewise Configuration

 

 

Comparison of Centralized Vs Decentralized UPS Systems   The following table shows comparison of Centralized Vs Decentralized UPS Systems   Description Centralized UPS Distributed UPS Distributed UPS-Zonewise Cost of Ownership Lower (Capital cost of Purchase + Operating Cost) Higher (Capital cost of Purchase + Operating Cost) Intermediate (Capital cost of Purchase + Operating Cost) Reliability High if the UPS configuration is N+1 but if there is a failure, all the loads connected to this UPS will be disconnected When compared with centralized UPS, the reliability of Decentralized UPS is better. A single failure will lead to shutdown of that specific load and not all the loads as in centralized configuration When compared with centralized UPS, the reliability of Decentralized UPS zonewise is better. A single failure will lead to shutdown of that specific zone and not all the loads as in centralized configuration Installation Cost Will be higher, as the distribution system has to be designed first Simple and easier due to plug & play system Will be Medium, as the distribution system has to be designed to the specific zone Safety There are no issues of safety as the UPS will be installed in an isolated place like electrical panel room With distributed UPSs, since they are kept close to the equipment they protect, the heat released from a UPS can damage the load or even give rise to fire problems due to battery failures There are no issues of safety as the UPS will be installed in an isolated place like electrical panel room Power Distribution and Quality Distance from the load creates power distribution problems for centralized UPSs. Extensive cabling is required if the area is large Decentralized UPSs are situated close to the load and hence quality problems such as harmonic distortions and noise are minimal Decentralized UPSs are situated close to the load and hence quality problems such as harmonic distortions and noise are minimal Enhancement of backup time Possible with addition of battery bank Generally, becomes difficulty due to the restrictions in charging current   Capacity Enhancement Limited to Planned capacity enhancement by paralleling UPS of same capacity & model. De-Centralized UPS is much effective than a centralized UPS configuration under planned or unplanned growth conditions. It’s simpler as we have to add a new UPS for the new loads which are getting connected. Limited to Planned capacity enhancement by paralleling UPS of same capacity & model. But flexible if new wings or floors added are protected zonewise Maintainability Medium High, as it gives the flexibility to service the UPS systematically without down time to all the loads. Medium, as it gives the flexibility to service the UPS zonewise without down time to all the loads. Impact of Single point of failure High, as a single fault in the UPS distribution system can lead to the complete shutdown of critical loads Low, as a single fault in the distribution system can lead to the shutdown of the loads connected to that particular UPS and not all the loads Medium, as a single fault in the distribution system can lead to the shutdown of the loads connected to that particular UPS in the zone and not all the loads Remote Monitoring & Alarm logging Can be done in an centralized location with an single screen More complicated as we need to monitor more numbers of UPS and an additional NMS System might be required for centralized monitoring More complicated as we need to monitor more numbers of UPS and an additional NMS System might be required for centralized monitoring Manageability The services can be easily managed and the cost of service will be less Prone to failure and the manageability of multiple UPS makes it a cumbersome job The services can be easily managed and the cost of service will be medium Product Reliability Will be higher Lower Medium

 

 

3- Hybrid UPS Configuration   Sometimes a combination of decentralized and centralized UPS will be more beneficial for the organization. The two strategies can be used in combination to provide redundancy to mission critical applications. For example, an entire facility may be protected by a large, centralized UPS, but a specific department such as a 24x7 call center may have decentralized UPSs as well to provide redundant protection and possibly extend runtime for call center equipment.

 

 

Conclusion: The decision on which system best fits a particular situation often depends on three factors: operations, reliability, management.   In addition, each option has its own advantages and disadvantages, but by giving full consideration to each UPS solution and the needs of the load and the requirement of organization, the designers can better determine which of these strategies is best suited.

 

 

Second: Conventional (Monolithic) Vs Modular UPS System

 

 

Data centers with fluctuating needs or future requirements that are difficult to forecast can employ Three strategies to increase the scalability of their UPS deployment: Deploy UPSs in parallel, Deploy UPSs in Series, Use modular UPS products.

 

 

1- Deploy UPSs in parallel   Parallel UPS architectures boost scalability as well as redundancy. As their power needs increase, organizations can simply add more modules to existing UPS systems, rather than replace current devices with new ones (see Fig.4) If any UPS fails completely, the other systems can keep protected information technology equipment (ITE) loads operational. Parallel UPS systems all feed the output bus, so any single UPS module can be isolated for maintenance or in case of a failure. Parallel systems must be synchronized together to share the loads.   Fig.4: Parallel UPS systems

 

 

2- Deploy UPSs in Series   In a serial architecture, multiple UPSs are connected end to end such that if any one UPS in the string fails, the others can compensate automatically.    Fig.5: Serial UPS systems

 

 

3- Use modular UPS products   Modualrity refers to: An engineering technique that builds large systems by combining smaller systems, A systems components maybe separated and recombined, Use of exchangeable parts or options in the fabrication of an equipment.   Some newer UPSs feature modular designs that allow you to add capacity incrementally as requirements increase.  For example, some such systems provide up to 50 or 60 kW of capacity in 12 kW building blocks that fit in standard IT equipment racks. As requirements increase, another 12 kW unit can simply be plugged in. For mid-sized power requirements, building blocks of 50kW may be the best financial solution, allowing scaling from 50 or 100 kW up to 300 to 400kW very easily. Even the latest generation large UPS systems are available in modular 200 to 300 kW increments. That is a scalable and efficient approach to keeping up with escalating power needs that also lowers upfront capital spending and conserves equipment room floor space.

 

 

Important note: Keep in mind that, for either of the above options, the premises wiring should be sized for the maximum possible UPS size, so that future re-wiring will not be necessary as the UPS system grows.

 

 

From the above three strategies we have two types of UPSs (see Fig.6): Conventional (Monolithic) UPS, Modular UPS System.   Fig.6: Conventional VS Modular UPS Systems

 

 

1- Conventional (Monolithic) UPS   Conventional UPS system is built mostly based on monolithic concept i.e. a UPS system will have a rectifier and inverter bridge of its rated capacity to support the loads. The conventional UPS can also be based on modular construction concept i.e. a UPS system will have 2 or 3 subassemblies of rectifier and inverter bridge which works together to form the full capacity of the UPS. The conventional UPS systems can work in standalone configuration or can be paralleled to improve the capacity or to improve the redundancy levels.   The Monolithic UPS will have: Low Component Count, which gives High MTBF, Fixed Components, which gives High MTTR.   Where: MTBF mean time between failure (a measure of reliability) MTTR mean time to repair (a measure of maintainability)

 

 

2- Modular UPS System   The modular UPS will be built up with multiple smaller UPS modules and number of UPS modules is paralleled to achieve the desired level of redundancy. Modular construction concept will have the same characteristic like monolithic UPS but will have higher availability. The modular UPS will exhibit a: High Component Count, which gives Low MTBF, Hot swappable UPS module, which gives Low MTTR.   The key advantages of Modular construction when compared with monolithic construction are: Power Modules: Based on standard pre-engineered modules and offer Inter - operatability of modules, Internal Redundancy: N+1 Redundant Fans & Failure of modules will lead only to reduced UPS capacity, MTTR: Shorter mean time to repair, Accessibility: Front Access Design with slide out Modules for easy serviceability, Flexibility, Right Size of Infrastructure, Scale up or Scale down based on the load agility, Quick to deploy, Availability, Use of exchangeable parts or option in the fabrication of an equipment, Total Cost of Ownership.

 

 

Example#1: Availability Comparison of Monolithic vs Modular UPS     Standalone 1+1 Parallel N+1 Parallel Redundant System N+1 Modular Parallel Redundant System   MTBF 2,50,000 Hrs 6,00,000 Hrs 5,00,000 Hrs 4,00,000 Hrs MTTR 6 Hrs 6 Hrs 6 Hrs 0.5 Hrs Availability 99.998% (4.9’s) 99.9990% (5.9’s) 99.9988% (4.9’s) 99.9999% (6.9’s) Redundancy Level 0% 100% 67% 67%   Example#2: Comparison of Foot Print Monolithic vs Modular UPS   Falcon N + 1 Modular System Monolithic 1+1 Parallel Monolithic N+1 Parallel Redundant Falcon N+1 Monolithic 1+1 Parallel Modular System Load 250KVA 250KVA 250KVA Installed UPS Capacity 2# 250KVA 3# 160KVA 1# 300KVA Configuration 1+1 N+1 N+1 Dimension 2# 1000 x 900 (WxD)mm 3# 710 x 900 (WxD)mm 1# 600 x 1000 (WxD)mm Foot Print 1.80m² 1.92m² 0.602m² Density 125KW/m² 117KW/m² 375 KW/m²

 

Comparison Of Conventional Ups Vs Modular UPS   Description Modular UPS Conventional UPS Footprint Required Due to vertical paralleling, the footprint required is less Requires higher footprint as a result of horizontal paralleling MTBF Low as there are numbers of modules connected in parallel, High as the number of systems in parallel is comparatively less MTTR Low due to hot swappable power modules Higher Single Point of Failure (SOP) Probability High,due to common battery bank, input & Output connections Low,as the single point of failure will be only in the common parallel bus Scalability Can be done online without disconnecting in multiples of modules capacity Can be done offline Efficiency Better due to right selection of capacity Lower due to over dimensioning Cost of Investment Higher Lower Operation Cost Lower Higher

 

Conclusion: Overall, we have seen how choosing a UPS system with the right modular topology supports the vision of enterprises seeking the benefits of a modular data center approach. The scalability of the UPS system can easily match that of the entire data center. UPS capacity can be quickly and incrementally added to match growing loads, without interruption to the power supply or disruption within the data center building. All of this can be achieved whole enjoying high levels of UPS efficiency and minimal need for cooling. At the same time, hot swap modularity allows up to 99.9999% availability – a consideration never far from any data center operator’s mind. Modular UPS approach isn't always the best solution to all scalable UPS needs, but it should be thought over as a part of a general UPS strategy. In addition, in order to see the entire picture, selection of a modular approach requires thorough knowledge of the particular UPS design including detailed information about common items like controller and battery.

 

In the next Article, I will continue explaining other Classifications of UPS Systems like:

9- Use of transformers.

So, please keep following.

 

Subject Of Pervious Article	Article
Applicable Standards for UPS Systems What is a UPS? Why do we need a UPS? UPS Rating Classification of UPS: 1-Voltage range, 2-No. of phases, 3- Mobility, 4- Technological design,	Classification and Types of UPS – Part One
5- Physical Size/capacity, 6- Form factor/ configurations: 6.1- “N” System Configuration	Classification and Types of UPS – Part Two
6.2- “N+1” System Configuration, which includes: Isolated Redundant Configuration (N +1) Parallel Redundant Configuration (1+1) Parallel Redundant Configuration (N +1) Parallel Redundant Configuration (N +2) and so on   6.3- Parallel Redundant with Dual Bus Configuration (N+1 or 1+1)	Classification and Types of UPS – Part Three
6.4- Parallel Redundant with STS Configuration Parallel Redundant Configuration (1+1) + STS Parallel Redundant Configuration (N+1) + STS   6.5- System plus System 2(N+1), 2N+2, [(N+1) + (N+1)], and 2N	Classification and Types of UPS – Part Four
7- According to UPS Topology 7.1 Off-line or Standby UPS, 7.2 Line Interactive UPS, 7.3 Standby-Ferro UPS, 7.4 Online Double Conversion UPS, 7.5 The Delta Conversion On-Line UPS.	Classification and Types of UPS – Part Five