Application of UPS power supply in various industries

1. Types of UPS

Generally, an economical choice is made with regard to UPS for the specific equipment in question based on such factors as reliability of power supply, functional, as well as other requirements. Depending on different load characteristics, there are quite a number of UPS types that can be selected. Types of UPS systems can be considered in the following order in order to make the selection easier and more practical:

Operating in Single Unit, used as backup;

Bypass Conversion impact exists and not impact;

Inverter regularly functions normally and mains regularly.

2. Characteristics of Power of UPS

One operation single UPS is for general essential load; Used for loads with different input and output frequencies or very low impact on Mains power and high frequency accuracy requirements.

Redundant operation of UPS, having a number of uninterrupted devices with redundancy capability. When some elements fail to operate, the functioning elements provide power to the load which is considered to be vital.

Bypass conversion UPS exists, and the load can be supplied with mains and inverter power hence enhancing power supply reliability. Most of UPS systems incorporate bypass systems.

Non bypass conversion UPS provides support for loads with different input and output frequencies, or with very high compliance standards of mains frequency and voltage.

In the predetermined normal condition of inverter operation, the load is highly sensitive to power quality and is purely of secured power supply voltage and frequency.

Purely during normal functioning of the mains powered load does not exhibit the same power quality requirements, only reliability, whereas the steady switching operation is very efficient. Integrate three operating modes based on the characteristics of the load during operation.

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3. Principles for applying UPS within power supply system

3.1 Load Considerations

The following questions come to mind. Is there an identifiable risk of power supply disturbance? To put it succinctly, in the absence of a power disturbance, a UPS should not be installed. The customers load power decides the level of importance of the load and this is derived from the degree of abnormal power supply damage sustained by the load. Such d damage encompasses both direct as well as indirect losses. The one that is direct twenty-five dollars and has a defective product in a production line and twenty-six dollars and data of some importance is lost in technology development and research. Indirect damages are the time taken to get the power back on and the reputation of the organization within the community. UPSevaluate how much damage has been caused, use this to evaluate the total investment of UPS system, decide if greater reliability is needed to justify the installation of UPS, if bypass and backup for UPS are going to be installed and finally the mode of operation is determined.

3.2 Effect of Power Quality on the Load

The quality of power, as it relates to the load includes the: acceptable range of the drop in voltage and its duration during power supply; range, the level of frequency accuracy for the daily voltage distortion. The load exert some serious bearing on the quality of the power which acts to simplify the system, reduce costs and enhance reliability. For instance, when a bypass is created, a typical 0.02-0.2s instantaneous power off conversion is appropriate. Daily voltage distortion, frequency accuracy is not usually a special load, adequate for use under mains supply and usually the effect of supply on load does not need to be catered for. Devices like computers which are sensitive to instantaneous drop in the voltage of supply and moments of power up cut experienced even when a hundred percent voltage cut for half cycle is experienced have effects. There is need for high quality power supply.

3.3 Selection of UPS Capacity

On the other hand, several factors have to be taken into consideration in estimating the size of the UPS; these include: characteristics, estimated load, Impulse current, peak currents, overload capacity, and rate of change of load.

The compensation of the effective load capacity is done with the following values.

(1) On Impulse Current

The peak current carrying ability of a UPS is determined by the load capacity and the peak impulse current, which is typically about 5-10 times the effective capacity, the rated current of the UPS.

When computers and peripheral devices are switched ON to the power supply, anticipation of a surge of current due to power on is expected. Load sequentially turned ON or mains operation to reduce the UPS capacity. When the current goes down below the rated voltage or current value, it switches to rectifier and inverter without voltage or current interruption for power supply.

(2) On Peak Current

UPS providing basic surge current parameter;

Carry Capacity= Loaded current rating of the UPS X peak – maximum value / allow able rating of the UPS;

The peak factor normal ranges up to 2XS of the effective capacity analysis;

A standard 2.5 times of the peak factor allow a more than 250% PA to sustain on a peak current, yet the limit is always rated limit of UPS and thus supports the system without any form of compensation.

(3) On Over Load

The overload issued for most UPS is above 1.1 effective loads from the standard, and anything above 1.1 from the standard should have protective measure enabled for the UPSs.

(4) Sudden load variation

The magnitude of the most UPS loads changes instantly by as much as 100%, and the output voltage variation can be maintained within 10% l~A. Therefore, effective load capacity compensations can be omitted.

(5) Generator and UPS system cooperation

Some places, after a power blackout occurs in the city, the UPS relies on a self-contained generator for power supply. When powered using a self-contained generator, self-contained generators are expected to be able to provide a large current surge during the UPS startup without compromising the stable working of the self contained generator.

a. Select rectifier equipment which less current on the starting of UPS. self-contained generators for 12 pulse rectifier systems should be double the capacity of rectifiers.

b. Enable several groups of UPS in parallel but delay their startup. It is also quite appropriate to combine this with ramp start: this will prevent excessive surge current flowing when all UPS are started practically at the same time.

c. The rectifier charger of the UPS should have controllable input. In this regard, the rectifier charger would provide limited power input while there is a back up from the batteries for the missing power.

d. Use only the UPS with a limited charging current function. When starting the generator this time, turn the charging off and set the charging current to 0A. It is possible to stop the charging current while the generator is active and so the power consumed by the UPS gets reduced from that supplied by the generator.

tor is running, thus decreasing the power drawn by the UPS from the generator.