Transformers Boost The Safety Quotient Of UPS Systems And Inverters

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Transformers are needed in UPS systems and inverters. They step up the voltage of the UPS system’s output to deliver the critical load in the same voltage rating as the input (mains).

By Potshangbam July

The demand for uninterruptible power in India is continuously increasing, particularly from the industrial and private sectors. However, the availability of uninterruptible power is still a distant dream, given the big gap between the demand and supply of electricity. Consequently, the reliance on back-up power devices, such as UPS systems and inverters is on the rise. As a result, the demand for transformers to make the relay systems operate in a smooth and safe manner has also increased.

Characteristics of transformers
Transformers are completely static solid state devices, consisting of two or more coils of wire. They are used to transfer electrical energy from one circuit to another by means of magnetic coupling. They play a major role in ensuring the trouble-free operation of UPS systems and inverters, by stepping up/down the voltages at each end of the line. They help to provide a safe and reliable power source.

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Listed below are some of the characteristics of transformers:

  • They can convert high and low voltages, but cannot change current from AC to DC.
  • The frequency of the input and output power is constant.
  • They can either decrease or increase the voltage as per the requirements.
  • All transformers operate on Faraday’s electromagnetic induction laws.
  • The primary and secondary coils do not have an electrical connection (except for auto transformers). The transfer of power is through magnetic flux.
  • No moving parts are required to transfer energy, so there are no losses due to friction or windage, like in the case of other electrical devices.
  • The energy loss in transformers is much less compared to other devices.

Types of transformers
Transformer based and transformer-less UPS systems are more or less similar in terms of working principles and key power quality performance. The main difference is in the design, wherein one has an inbuilt integrated transformer and the other doesn’t (refer the box on next page).

Main hurdles to overcome
The main challenge the industry needs to tackle is the absence of mandatory specifications and guidelines for the installation and maintenance of transformers. The awareness levels about the importance of technical details and parameters in transformers are low; so consumers tend to ignore the safety features while purchasing these. Besides, the sector is predominantly unorganised, with high penetration of inferior Chinese products that are available at cheap prices. Price based sales tactics easily entice the consumers, and the players involved in the distribution of these products are also small. Another problem is the non-availability of the core raw materials used in transformers, both CRGO (cold rolled grain oriented) and amorphous, so they are imported from other countries. Also, in most cases, manufacturers end up using sub-standard raw materials. This creates instability in the market, with fluctuations in price from one location to another.

Maintenance and care
To ensure quality and safety during operation, proper maintenance needs to be done on a regular basis. It is crucial for the UPS systems and inverters to undergo various tests in tune with the specifications to detect any defects and faults that may cause breakdowns. Without proper care, the accuracy and efficiency of transformers tend to deteriorate, culminating in the ineffectiveness of the system. One should fix problems like leakage and the ingress of oxygen and moisture at the earliest, as this has the potential to cause explosions, resulting in loss of life and material. Other external factors, such as design errors, overloading or underloading, manufacturing defects, etc, can accelerate the aging process of the transformers.

Transformer based UPS systems Transformer-less UPS systems
The transformer, which is at the output of the inverter, provides a galvanic isolation between the DC bus and the output AC power. This transformer does not allow the DC to flow through the loads. There are additional electronic circuits to detect the DC component in the output but require an output transformer.
The battery life may be shortened drastically due to AC ripple They last more than 10 years.
They are low in efficiency with high operational costs. They are of high efficiency, which decreases electricity losses. As a result, operational costs are lower.
The impact on the environment is high due to the presence of more components and the large size for the unit. Environmental impact is low.
They are typically available from 10kVA, which is more suitable for industrial applications. They are lightweight and ideal for IT applications.


Purchasing guide

Selecting the right kind of transformers is important. The transformer should be able to provide solutions to your requirements. Listed below are the important factors that should be considered before purchasing a product.

  • Determine the voltage type: This is the output voltage or secondary voltage of the transformer. It is important to know the voltage type to prevent overloading with excess power.
  • The kVA requirement: Once the requirement of the voltage level is figured out, it is easier to select the right transformers. For this, you are required to do a calculation using the formula kilovolt ampere (kVA) = (volts x amps)/1000. The kVA of the transformer should be either equal to or more than the load value.
  • Number of phases: Transformers are usually available in single-phase or three-phase variants. Deciding between these will depend on the requirement of the user. Single-phase transformers are ideal for small household equipment whereas three-phase variants are incorporated in heavy equipment used in industries and factories.
  • Frequency requirements: The power supply usually determines the frequency of a transformer. It should be kept in mind that the frequency of the supply source and the load should be the same.
  • Location and environment: It is important to be aware of the location and size of the transformer for the installation process. Some transformers are meant for indoor use, having been designed without the rugged features that can sustain various kinds of environmental changes and conditions. Also, the transformer should not be placed in the proximity of hazardous substances or chemicals.
  • Lastly, all equipment are not the same, as their requirements are different. Some require an auto transformer and some equipment are best kept detached from the power supply.

The market scenario
There are major steps being taken by the government to strengthen the power transmission and distribution network. Thus, the demand for transformers will be increasing considerably. As per reports, domestic manufacturers have developed capabilities to manufacture all types of equipment to meet the country’s demand for transformers ranging from 800kV to 1200kV. The Indian power and distribution transformer market is forecast to reach US$ 2.9 billion by 2022.

Some of the interesting products available in the market

Product: UPS transformers, Manufacturer: Addya Electronics
These transformers are available in standard as well as modified forms.
Key features

  • Sturdiness
  • Long service life
  • Maintenance-free

Specifications

  • Ambient temperature: -15°C to +40°C
  • Relative humidity: <90 per cent
  • Efficiency: ≥ 95 per cent
  • Frequency: 50Hz or 60Hz

Contact: www.addyaelectronics.com

Product: Auto transformer, Manufacturer: Rishab Industries
An auto transformer uses common winding. Because it shares parts of the winding, an auto transformer with the same kilovolt ampere (kVA) output rating as a two-winding transformer is generally lighter and smaller.

Technical details

  • Three-phase power range: 1kVA to 1000kVA
  • Single-phase power range: 1kVA to 100kVA
  • Insulation class: Class H or Class F
  • Frequency: 50Hz/ 60Hz
  • Cooling type: Dry type/air cooled
  • Conductor: Strips/wires of copper or aluminium as per customer’s requirement
  • Core: CRGO or CRNGO type

Key features

  • Greater efficiency
  • Customised and compact designs
  • Good mechanical and short-circuit strength due to the VPI process
  • Moisture ingress resistant and immune to polluted atmosphere
  • High grade iron core and winding can be wire or foil

Contact: www.rishabindustries.com

Product: Voltage sensing transformer, Manufacturer: Wings Automobiles Products (Pvt) Ltd
This transformer can be used in inverters/UPS systems, electronic equipment and machinery.

Key features

  • Range: 3VA-100VA
  • Standards: IS 2026/11171, IEC60076
  • Insulation class: F
  • Voltage: 110V – 400V
  • Phase: 1
  • Frequency: 50Hz/60Hz
  • Conductor material: Al/Cu
  • Lamination: CRNO/CRGO

Contact: www.wingsauto.com

Product: Inverter transformer, Manufacturer: Custom Coils
These transformers are designed to be lightweight, small in size, and portable. They comprise primary and secondary windings. The AC is passed through the primary windings when the switching action takes place. This allows the transformer to control the level of voltage for the applications.

  • Key features
  • Input frequency up to 350KHz
  • Support for multiple topologies
  • Low signal distortion
  • High permeability
  • PCB pin mounting
  • Surface mounted
  • Through hole bobbin terminal

Contact: www.customcoils.com

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