Transformer Name Plate Details Fully Explained

Transformer name Plate Details:

Nameplate details are used to read about the transformer design. Every electrical engineer must know how to read electrical power or distribution transformer’s nameplate details. Let start….

Transformer Name Plate Details
Transformer Name Plate Details

Manufacturer Details:

First they give the transformer manufacture details. From that anyone can easily identify the name of the original transformer’s manufactures.[wp_ad_camp_1]

Vector group:

Vector group tells about the winding connection such as star configuration or delta configuration and winding connection. Most of the power transformer or control transformer uses Dyn11. Which means D-delta connection, y-secondary star connection, n- neutral connection and 11 mentions that the phase shift 30 deg anti close wise. Here vector group mentions that the primary voltage will be shifted by 30 in secondary side. Because of vector group is very important for doing parallel operation of the transformer.

Must See: Three Phase Transformer Vector Grouping Significance of Vector Grouping

WTI Ratio: 4205/5 Amps, Class-5, 20VA

WTI current transformer is an internal, only one transformer which is used to protect the transformer if all the circuit fails. It is a backup protection for the transformer. In this WTI is Winding temperature indicator of the current transformer, CT ratio means of the line current transformer is 4205/5 amps. Class 5 of the transformer is approximate accuracy class. 20 VA means the burden of the current transformer.

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Transformer Tap circuits:

That is used to increase or decrease the output voltage of the transformer, the taping mention in number and they have some percentage of the voltage ratio, typically 0.1 to 5 percentage. Mostly distribution transformer comes with the off-line tap changer and power transformer comes with on-line tap changer circuits.


  • The tap changer circuits will be placed in HT side of the transformer. See here why
  • Off line tap changer should be operated when the transformer is de-energized.

NCT: 4500/1A, 5P10, 15 VA

NCT is nothing but a Neutral current transformer. It comes with the protection class. Neutral CT output can be used in restricted earth fault protection or standby earth fault protection.

Also see: Different types of Protection Class used in Protection System

Basic insulation level:

It mentions the dielectric strength of the insulation under various voltage level.

Also see: How to Find Insulation Aging of the Transformer

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Rating: 3150 kVA

It means the rated capacity of the transformer. Transformer normally mentions in kVA rating. See here why

Also see: Frequency Vs KVA output Rating of the transformer

No load voltage:

HV side: 11000 Volts, the rated input voltage of the transformer under No load condition

LV side: 433 Volts. The rated output voltage of the transformer under No load condition

The output current:

The secondary and primary rated current of the transformer. That is full load capacity of the transformer.

Phase: 3 => Three phase

Frequency 50 Hz => Input and output frequency if the transformer

Cooling of the transformer => ONAN => Oil natural Air Natural. The transformer body will be cooled by transformer wings and open air.

No load voltage: the output voltage of the transformer under No load with different tap position.

Ref: I.S = 2016

The transformer has made in Indian Standard procedure number 2026.

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Maximum Ambient temperature: 45 deg.

The allowable surrounding temperature is 45 deg.

Impedance percentage: 6.76%

If you load the transformer 100 % means the output voltage will be decreased by 6.76 % which means

Take secondary no load voltage: 433Volts means, if you load the transformer by 100% then the output will be 433- (0.0675 *433) = 404 Volts.
Core, oil and winding Weight: All says the total weight of the individual part.

Also see:



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