Today, with technological advancements, the power loss of static UPS systems has gradually decreased. Early online UPS systems with input and output transformers and employing thyristor technology (referred to as double-conversion UPS or IEC "VFI") had a full-load operating efficiency of only 83%-85%. Currently, high-frequency online interactive UPS systems using IGBT (Inductively Coupled Bipolar Transistor) technology can achieve a full-load efficiency of 95%-97%.
More efficient, less calories
Today's UPS systems offer 15% higher energy efficiency while reducing cooling requirements, thus improving reliability. Modular UPS systems have seen their mean time between failures (MTBF) increase from less than 25,000 hours to 150,000 hours; output voltage waveform distortion decrease from 5% to 1%; noise levels drop from 95 dBA to 70 dBA; and footprint is reduced by as much as 90%.
Even with double-conversion UPS systems, efficiency reaches 96.8%, and the cost per kilowatt of capacity has dropped to its lowest level ever. This is beneficial for users, but the only way for manufacturers to profit from UPS systems is by providing after-sales service.
European manufacturers have largely eliminated transformers in their UPS systems, while in North America, transformerless UPS systems are still a novelty. Manufacturers like APC have adopted an online interactive topology, which, although lacking frequency protection and not technically "online," still works well in stable power grids.
In the 1990s, Invertomatic introduced an ECO mode UPS in Switzerland (its operating principle is shown in Figure 1), but market sales were not optimistic. Later, modular UPS systems from industry manufacturers solved the partial load problem for most data centers. The principle of ECO mode is simple: when the mains power is stable, the UPS automatically switches to bypass mode to reduce power loss, especially for transformerless UPS designs. In this mode, the UPS rectifier still operates to charge the battery (requiring much lower power than a flywheel UPS), while the inverter is in standby mode. The bypass (thyristor switch) is activated to supply power to the load until a power anomaly occurs. At this point, the UPS static switch transfers the load to the inverter. A significant drawback of UPS operating in this mode is that there is no improvement in power quality when the UPS is operating in bypass mode.
Figure 1
Some "advanced" economical UPS switching models now have a switching time of 2ms instead of 4ms, and some even monitor load distortion and make decisions about the power grid. However, the basic idea remains the same: if the power supply is stable, then energy can be saved.
However, this often carries risks, and the economic model remains largely unchanged. Whenever there is a power deviation, the load switches from bypass to normal mode, which is the exact opposite of the protection provided by a double-conversion UPS. This switching means the load is exposed to risk, and although this risk may be small, the user must weigh it against the potential rewards.
With rising electricity costs and the promotion of the concept, the economic model has been accepted; however, efficiency is not always the most important indicator that users expect.
UPS systems using silicon carbide (SiC) are more energy-efficient and effective.
UPS operating in economic mode has significant advantages, but the newly developed silicon carbide technology may offset these advantages. Currently, transistor manufacturing relies on traditional silicon controlled rectifier devices, while for UPS, insulated gate bipolar transistors (IGBTs) are becoming increasingly powerful and reliable.
A significant drawback of UPS systems using IGBT devices is that the faster the switching speed (to achieve higher accuracy), the greater the power loss. This is mainly because the module efficiency has an upper limit of 96.8%, while using silicon carbide devices can theoretically increase the efficiency of double-conversion UPS systems to 98%~99%.
Synthetic silicon carbide powder has been mass-produced since 1893. IGBTs made with silicon carbide were initially expensive, but they also offered significant energy savings, and none of this involved shifting critical loads to the grid or increasing the risk of power conversion.
At the module level, silicon carbide offers two main advantages: smaller chip size and lower dynamic losses. At the system level, these advantages can be leveraged in several ways. Low dynamic losses result in a significant increase in output power, providing opportunities for weight and size reduction. Notably, this power increase can be achieved without additional cooling capacity because silicon carbide offers virtually less power loss compared to silicon controlled rectifiers, allowing for higher output power under the same cooling conditions. Low power losses improve energy efficiency, allowing for the design of more efficient inverters, thus making UPS applications more energy-efficient.
Therefore, using silicon carbide eliminates the need for UPS to operate in economy mode, and can even replace line-interactive UPS systems. When users can obtain comprehensive protection against voltage and frequency fluctuations with less than 1% energy loss, who would need a UPS operating in economy mode?
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About Invt:
Founded in 2002, INVT is committed to becoming a leading and respected global provider of products and services in industrial automation and energy. It was listed on the Shenzhen Stock Exchange A-share market in 2010 (stock code: 002334). INVT is a key high-tech enterprise under the National Torch Program, currently possessing 16 holding subsidiaries and 12 R&D centers across China. It has applied for over 800 patents and relies on key technologies in power electronics, electrical drives, automatic control, and information technology. Its main products cover high, medium, and low voltage frequency converters, elevator intelligent control systems, servo systems, PLCs, HMIs, SVG, UPS, motors and electric spindles, photovoltaic inverters, rail transit traction systems, and new energy vehicle electronic control systems. INVT currently has over 2,500 employees, three large-scale production bases, and a marketing network covering more than 60 countries and regions both domestically and internationally.
