EPS and UPS

EPS is designed primarily to address the power supply needs of critical equipment such as emergency lighting, accident lighting, and fire protection systems. It provides an emergency power supply system that meets fire safety standards and features independent circuits; this system can supply power in emergency situations, to meet lighting requirements when there is only one source of electricity available, to serve as a second power source in place of generator sets, or to be used in situations where a third power source is necessary. EPS is fundamentally different in structure and working principle from the uninterruptible power supply (UPS) that emerged with the development of the information industry. EPS is primarily designed to meet the special emergency requirements of emergency power supply systems, such as high reliability, high efficiency, the ability to handle mixed loads, overload capacity (ability to operate normally at 120% load), environmental adaptability, and self-diagnosis functions; it remains in standby mode (OFF LINE) most of the time, and only activates the inverter system when such emergency conditions arise ； UPS systems are designed primarily to meet the requirements related to the switching time of emergency power supplies, aiming for zero switching time, input-output phase locking, and high accuracy in voltage and frequency regulation. Nowadays, most UPS systems operate in online mode, meaning that the inverter system is always active; as a result, they have low efficiency, poor adaptability to loads and environmental conditions, and limited overload capacity (usually 60-80% of the nominal value). It differs significantly from UPS in terms of working principle, operation mode, performance metrics, structure, selection, installation, and maintenance. Accurate understanding, design, manufacturing, application, selection, and maintenance are essential conditions to ensure the long-term reliable operation of EPS. An EPS generally consists of a charger, battery pack, inverter, automatic switching device, input/output components, battery monitoring device, control system, status display, operation panel, and other components.

This post was last edited by zhaohh3211 on 2010-8-18 11:15. EPS is an emergency power supply, while UPS is an uninterruptible power supply. The difference in the load carried by the two is as mentioned on the 2nd floor. Everyone is familiar with UPS, while EPS is mainly used in situations where there are strict requirements regarding power supply duration in the event of a power outage, and the load must not lose power. The price of EPS is high, and it is also sensitive to load. The requirements for the qualifications of maintenance personnel are also correspondingly high. If there are no special requirements regarding power supply duration, choosing a diesel generator is by far the most economical and convenient option.

Differences between EPS and UPS: Principles and Structure

| Serial No. | EPS | UPS |
|-------------|-----|-----|
| 1 | High inverter redundancy | Low inverter redundancy |
| 2 | Input and output cabinets; no such cabinets inside the EPS unit | No input or output cabinets inside the unit |
| 3 | Motors require variable-frequency starting | No need for variable-frequency starting |
| 4 | Can be integrated with fire protection systems | Unrelated to fire protection; no need for flame-retardant measures |
| 5 | Flame-retardant casing and wires; multiple switching functions available | No switching functions available |
| 6 | Special measures for dehumidification, mold prevention, and rodent control required | No special measures required |

Other differences:
- EPS: Target loads are inductive or resistive types; low inverter redundancy.
- UPS: Used for motors, water pumps, fans, and lighting; no input or output cabinets inside the unit.
- Key feature of EPS: Strong ability to adapt to various loads; no need for variable-frequency starting.
- Purpose of EPS: To ensure reliable emergency power supply; unrelated to fire protection, so no flame-retardant measures are needed.
- Installation location: In building shafts or distribution rooms; no switching functions available.
- EPS is a fire protection product, designed as a specialized emergency lighting power source for centralized emergency power supply; no special measures are required.

Advantages of EPS over UPS:
| Parameter | EPS (Three-phase Emergency Power Supply) | UPS (Uninterruptible Power Supply) |
|-----------|--------------------------------------|------------------------------------|
| Power saving | In sleep mode when the grid is supplying power, consumption is less than 0.1%; efficiency is over 92% when there is no grid power. It also operates when the grid is working, but with an efficiency of only 85–90%, resulting in about 10–15% of electrical energy being wasted. | Saves 10–15% on power consumption. |
| Noise | No noise when in sleep mode due to no operation when the grid is supplying power; produces noise when there is no grid power. | |

This post was last edited by zhaohh3211 on 2010-8-18 11:28 {:3_47:} Don’t you know about MUPS and DC-BANK?

One more thing: EPS is essentially an inverter； Meanwhile, a UPS includes a rectifier and an inverter. In fact, a UPS can be understood as an inverter that is capable of outputting only a 50Hz frequency. Therefore, UPS is suitable for applications that require a stable AC power supply for normal operation, such as computers, networking equipment, communication devices, and DCS systems, while inverters serve as a second or third power source, acting as a replacement for diesel generators.

This post was last edited by zhaohh3211 on 2010-8-18 11:31. In simple terms, EPS is a backup-type UPS.

EPS will experience a brief power loss during the switching process; this should be taken into account when selecting an appropriate power source for the load !

Reply to 1# Farming, Seafood Fishing, Animal Husbandry, and Fisheries: III. Similarities and Differences between EPS and UPS. 1. EPS is an evolved form of UPS technology. In advanced countries in Europe and America, due to grid-powered supply, there is an ample supply of electricity of good quality. Additionally, electrical equipment there meets certain standards, preventing it from causing pollution or interference in the power grid. Therefore, in many situations, dual-inverter online UPS units are not recommended; instead, UPS units operating in energy-saving ECO (ECONOMY CONTROL OPERATION) mode are advised. In this mode, the load is normally powered by mains electricity, and when the mains power fails, power is supplied by batteries through an inverter. In Europe, such UPS units that operate in an energy-saving mode are called CPS (Center Power Supply). They are widely used because online UPS systems with dual-inverter operation achieve an energy conversion efficiency of around 90% when the mains power is stable; whereas UPS units in energy-saving mode (CPS, EPS) have an energy conversion efficiency as high as 99% under the same conditions. Moreover, the availability of the grid power supply exceeds 99.99%, meaning there is only a 0.01% chance of power outages. Therefore, using CPS (EPS) for power supply results in significant energy savings. At the same time, the EPS inverter is in a startup state but does not output power, similar to a dormant state; this allows the EPS inverter to have a **longer lifespan** compared to the inverter in a UPS, as it can continue to output power. In fact, the high-end products of EPS are UPS in standby mode. When the mains power is normal, although EPS has inferior power transmission quality compared to UPS, it can meet the requirements of most electrical devices in today’s world where systems are connected to the mains grid. Therefore, with concerns over the eternal issue of power saving and high reliability, EPS is generally superior to UPS. If the power grid quality is good, power supply is reliable, and electrical equipment meets standard specifications, in many cases in China it is possible to use EPS to replace dual-inverter online UPS, rather than using UPS to replace EPS. Of course, for some very critical equipment, dual-inverter online UPS is still required. 2. Differences between EPS and UPS: (1) The development of EPS in China originated from the need to ensure power supply continuity in case of sudden grid failures, as well as to support fire-fighting operations. It can provide emergency lighting and power for firefighting purposes, thereby protecting people’s lives and health from harm. The technical requirements for such products are supervised by the fire safety certification authorities under the Ministry of Public Security, and they also require approval during installation. UPS is merely used to protect users’ equipment or businesses from financial losses, and its technical specifications are certified by the Ministry of Information Industry. The safety standards applicable to the two are significantly different, resulting in different set of values. (2) Both EPS and UPS can provide two separate output power supplies; to ensure high-quality power supply, UPS gives priority to the inverter option ； And EPS prioritizes mains power to ensure energy savings. Of course, there are differences between the two in terms of the design specifications for rectifiers/chargers and inverters. (3) Since UPS is used in an online mode, it can issue alerts promptly in the event of a failure, and with mains power as a backup, users can quickly become aware of the issue and resolve it, thereby preventing greater losses from occurring. EPS is used offline and serves as the final power supply backup; therefore, its reliability design requires higher standards. It cannot be simply regarded as a backup UPS, as doing so would undermine the importance of EPS. If the EPS cannot be powered by batteries in the event of a power failure, it is essentially useless, and the consequences would be disastrous. (4) UPS power is supplied to computers and network devices, and the nature of the load (input power factor) varies little; therefore, national standards specify that the output power factor of a UPS should be 0.8. The purpose of EPS power supply is to ensure electricity supply and fire safety; the loads involved can be inductive, capacitive, or rectified nonlinear loads. As a result, its output power factor cannot be set at 0.8 (national standards for EPS specify this value). Moreover, some loads begin to operate only after the main power supply is interrupted, which requires EPS to be capable of delivering high inrush currents. Therefore, EPS needs to have good dynamic performance and stronger overload resistance. Therefore, the technical design specifications for the various components of EPS and UPS are different.

EPS experiences brief power outages; if it is used to power systems such as central control systems, it will not be functional. Additionally, EPS batteries take up space.