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Retrofits For Industrial Transformers

Olsun Electrics Corporation has been providing retrofit for Industrial Transformers for over 40 years. Because of the unique capabilities in both design and manufacturing Olsun is able to meet the stringent requirements of replacing an existing transformer.

Transformers are very reliable and provide years of uninterrupted service. However, should replacement be necessary of either a Dry Type Transformer or Liquid filled Transformer it can become a challenge to retrofit a replacement.

There are a number of reasons for replacing an existing transformer

  • Natural disaster – Flood, Lighting, etc. – causing premature failure
  • Reliability – Transformer nearing the end of it’s useful life
  • Overloading – Due to increased loads or possibly Current Harmonics
  • Excessive moisture – causing premature failure
  • Leaking or other maintenance issues of a Liquid Filled transformer

Distribution transformers most often retrofitted are from 300 kVA and 5000 kVA and have primary voltages of 15 KV and below. The Distribution Transformer being replaced may be either a Dry Type Transformer or a Liquid Filled Transformer. Although Olsun Electrics does not manufacture Liquid Filled transformers on occasion a Dry Type Transformer is used to replace a Liquid Filled Transformer. When retrofitting an existing Dry Type Transformer a complete new enclosure may be required or more often a Core and Coil only is required to fit into the existing enclosure.

It is important to note retrofit Distribution Transformers per the definition as indicated by the Federal Regulation 10 CFR Part 431 must meet the efficiency requirements of this Federal Regulation.

The definition of a “Distribution Transformer” is as follows

  • Has an input voltage of 34.5 KV or less
  • Has an output voltage of 600 volts or less
  • Is operated at a frequency of 60 Hz
  • Has a capacity of 10 kVA to 2500 kVA for liquid filled and 15 kVA to 2500 kVA for Dry Type

The term “Distribution Transformer” does not include the following

  • Autotransformer
  • Drive (Isolation)transformer
  • Grounding transformer
  • Machine-Tool (control) transformer
  • Nonventilated transformer
  • Rectifier transformer
  • Regulating transformer
  • Sealed transformer
  • Special Impedance transformer
  • Testing transformer
  • Transformer with a tap range of 20 percent or more
  • Uninterruptible power supply transformer
  • Welding transformer

The Types of Transformers that have been retrofitted by Olsun Electrics are as follows

  • Distribution Transformers/Unit Substation Transformers – Dry Type and Liquid Filled – 225 KVA to 5000 kVA, 15 KV and below – Indoor and Outdoor
  • Secondary Termination to match Secondary Switchgear
  • General Electric
  • Eaton/Cutler Hammer
  • Schneider Electric/Square D
  • Siemens
  • Others
  • Drive Isolation – 6 pulse and 12 pulse
  • Test Transformers – Multi-tap for testing of electrical equipment
  • Rectifier Transformers – 6 pulse and 12 pulse
  • Furnace Transformers

Retrofitting a Transformer whether it is a Dry Type or Liquid Filled Transformer requires detail information regarding the existing installation.

Dry Type Replacement

In addition to the KVA, Primary voltage, Secondary voltage, single phase or three phase and temperature rise the following information is required to retrofit an existing Dry Type Transformer installation:

  • BIL (Basic Impulse Level) of primary winding and secondary winding.
  • Overall dimensions of the existing enclosure
  • Primary and Secondary termination Details
  • Location, spacing and phasing – a picture of primary and secondary terminations is helpful if possible
  • If Core and Coil only is required provide base detail dimensions of the existing transformer

Also, the location and access to the transformer being replaced needs to be taken into consideration. There may be critical height and/or width dimensions in order to move the retrofit transformer into the location of the existing transformer. In a multistory building there may be elevator weight and/or dimension restrictions. One solution to the issue of limited elevator weight and/or dimensions would be to provide a Dry Type Triplex Transformer. A Triplex Transformer consists of three single phase transformers in a common enclosure and bussed together in a three phase configuration. Each of the three single phase sections will be much smaller and lighter than an equivalent three phase transformer. The three single phase transformers can be moved to the location of the transformer being replaced and reassembled once in the location of the existing transformer.

Liquid Filled Replacement with a Dry Type Transformer

When replacing a Liquid Filled Transformer with a Dry Type Transformer the same basic information as indicated for the retrofitting of a Dry Type Transformers is required. However, since the Liquid Filled Transformer is normally less in width than the Dry Type Transformer, if may be necessary to rotate the orientation of the Dry Type Replacement enclosure 90°. In addition, the Liquid Filled Transformer would normally have primary and secondary throats which may not be required for the retrofit Dry Type Transformer. Eliminating the primary and secondary throats would free up additional space for the width dimension of the retrofit Dry Type Transformer. When the Dry Type Transformer is rotated 90° the depth dimension is normally increased relative to a design that is not rotated. Therefore, it is important to indicate the clearance dimension in the rear and in the front of the existing transformer.