UPS systems

An uninterruptible power supply system (UPS for short) is used to provide emergency power to connected loads in the event of a power failure.

UPS systems are essentially divided into three categories:

Offline / standby UPS systems of classification 3 according to IEC 62040-3: Offer protection against power failure, voltage dip and overvoltage. This type of UPS system offers the least protection, but at the same time represents the most cost-effective variant. It is called an offline or standby system because the system only takes over the supply of the connected loads in the event of a power failure. Due to the switching time, voltage dips of up to 10 ms often occur. Often, IT consumers, such as computers, can compensate for this delay so that no mains failure is noticeable at the consumer. These system types are therefore almost exclusively intended for computers or small EDP devices that do not represent mission-critical consumers.

Line-interactive UPS systems of classification 2 according to IEC 62040-3: Offer additional protection against short circuits in the public network and line noise. The Line-Interactive system is considered an intermediate stage between offline and online technology. In contrast to offline UPS systems, systems of this classification also smooth the output voltage so that they also protect the connected loads against voltage peaks and line noise. These types of systems are also suitable for the protection of computers and partly also for server systems, which do not represent mission-critical consumers.

Online UPS systems of classification 1 according to IEC 62040-3: Offer additional protection against high voltage peaks, frequency deviations, switching peaks and harmonic harmonics. UPS systems of the online classification provide optimum protection for your loads and can be used for business-critical applications. Due to the double conversion technology, there is no voltage interruption in the event of a mains failure and the loads are permanently supplied. In addition, systems of this category also protect against various types of voltage disturbances. Since the rectifier and inverter of the UPS system are permanently in operation, a pure sine wave is generated so that an optimal voltage supply is permanently provided for your consumers.

The required UPS power is directly dependent on the connected loads and their load profile. In order to correctly dimension the UPS system, the following information is required on the connected loads:

Power

Cosphi

Inrush current (overload behaviour)

Based on a corresponding load table, the maximum load current as well as the maximum inrush current can be calculated, which serves as the basis for UPS dimensioning.
We recommend a maximum load of approx. 60% for all UPS systems in order to take growth and power reserves into account.

The bridging time is directly dependent on the connected load and the installed battery system. The battery system for the UPS systems can vary from 1 kVA upwards, so this cannot be answered in a general way.

Depending on the connected load and the desired bridging time, battery systems can vary. Optimally, internal batteries installed in the housing of the UPS system are sufficient. In this case, the space requirement is minimal. However, with increasing requirements in terms of bridging time and load, it is often necessary to switch to external batteries that have to be installed on a separate rack or in a separate battery cabinet.

The majority of the UPS systems can be equipped with additional network cards or fault messages so that monitoring can be carried out via SNMP or a connection to the BMS.
However, these monitoring devices are often not installed as standard in the UPS system.

This also depends on the load to be supplied, as well as the desired / required bridging time.
Depending on the load to be supplied, standard-related requirements may also play a role. In principle, however, every UPS system should be freely accessible and there must be sufficient wall clearance for ventilation. This also depends on the performance of the UPS system.

Battery systems in particular are subject to technical standards requirements due to the gases they emit during heavy charging.

For battery systems, a distinction is usually made between 5, 10 and 12-year batteries. However, these are service life expectations under optimal conditions.

Experience shows that often only 70-80% of this service life expectation is achieved.

For UPS systems, regular maintenance is crucial for the service life maintenance of the system. With regular maintenance and the regular replacement of the necessary wearing parts, UPS systems can achieve a service life of 15 years.

According to DGUV V3, the operator's responsibility places the operator of emergency power systems under the obligation to carry out regular maintenance on electrical systems. Proper maintenance should be understood as an investment in the future. No operator of an emergency power system wants a system that does not take over in situations of power failure.

Therefore, maintenance work makes sense in order to be able to ensure the reliability and availability of your consumers even in the event of a power failure.

We recommend a maintenance interval of one year, this is also required in VDE 0105 for electrical systems and electrical equipment.

There are several advantages for the user or operator when using UPS systems to protect the connected consumers. The first and most important advantage is the protection of the power supply of, for example, server landscapes, sensitive measurement electronics and any kind of IT as well as, for example, cash register systems. In the event of a power failure, not only is the loss of data, measurement results or the defect of complex systems prevented, but it is even possible to continue working in the event of a power failure without interruption of the supply by the UPS system. The second advantage can also be, for example, to bring the "electrical imbalance" of the house connection and the main building distribution back into a symmetrical utilisation of the three outer conductors (L1,L2,L3) through the UPS system.