Hello, readers welcome to new post. In this post, we will have a detailed look at **Three Phase Transformer Per unit Impedance. **Three phases transformer is the main element of the system and operates at mutual induction phenomenon. according to that flux change in first windings induced volts in second windings according to that linking flux to the secondary windings.

In this post, we discuss the three-phase transformer per unit impedance. So let get started with

## Three-Phase Transformer Per unit Impedance

- In the normal configuration of 2 windings transformer primary and secondary windings has a similar value of KVA but in the three-phase, these values are not same.

- The impedance value of every winding of the transformer is given in per unit system or in percentage according to ratings.
- But there should be same value for base KVA in the above two methods of impedance definition.

- The design of the signal phase having three windings is shown. the windings are primary secondary and tertiary.
- A short circuit test is done to finds the impedance.
- ZPs is leakage impedance measured tough primary side having secondary s short circuit and tertiary as open.
- Zpt is primary impedance measured doing the short circuit at tertiary keeping the secondary s open circuit
- Zst at secondary measured at tertiary short-circuited and primary as open circuit

Now we have

Zpt= Zp+Zt

Zps=Zp+Zs

Zst=Zs+Zt

- In the above equations Zp, Zs, and Zt are impedance values at primary secondary and tertiary windings.
- By simplifying the above equation we have

Zp=1/2(Zps+Zpt-Zst)

Zs=1/2(Zps+Zst-Zpt)

Zt=1/2(Zpt+Zst-Zps)

- The impedance of 3 windings 3 coils are linked to a resultant circuit of single-phase 3 windings transformer connected to magnetizing current.
- The points P s and t are linked to the three windings of the transformer.
- In the case of 2 windings transformer, there is a need for a similar KVA base for 3 circuitry and needed voltage bases for 3 circuits having a similar ratio like the rated line-to-line voltage of the device.

## three winding transformer impedance

- Three-winding transformer impedance is normal resistance and reactance that causes a restriction to the current flow in the transformer. Normally it is measured in percentage. The percentage of the impedance of voltage if the transformer is operating at full load according to transformer capacity

## 3 winding transformer impedance calculation

The impedance of three winding transformer is measured as the secondary of the transformer is short-circuited. Voltage increases on primary till full load curent flows in the secondary windings. The voltage given is divided by rated primary voltage with 100 multiple is the value of the impedance of the transformer

Applied voltage/ rated voltage x 100= impedance

## percentage impedance of transformer

- The percentage impedance of a transformer is voltage loss at full load due to resistance of windings and leakage reactance shown as a percentage of rated volts. Percentage of normal terminal voltage needed to measure full load in short circuit conditions

**Read also:**

- How to Replace Doorbell Transformer With Diagrams
- Introduction to Ideal Transformer, Working, Phasor Diagram, & Circuit
- Transformer Ratings and Rating Problems
- Transformerless 6V DC Power Supply
- Transformer Ratings and Rating Problems

#### FAQS

**What is the impedance of a 3 winding transformer?**

- impedance tolerance value for 3-winding transformers is ± 10%, not ± 7½%,

**How do you calculate the impedance of a three-winding transformer?**

- The impedance of the transformer is used with using formula
- Applied voltage/ rated voltage x 100= impedance

**What is the impedance of a transformer per unit?**

- The per-unit impedance is the
**percentage of the rated voltage needed to generate full load current when the transformer output is shorted**. If impedance is less then low volts are needed to generate full load current.

**How do you calculate the impedance of a transformer?**

**applied voltage divided by the rated primary voltage with product of 100**is the impedance of the transformer.

**What is the impedance of 75 kVA transformer?**- A 75 KVA transformer impedance be from
**2.7% to 5.75%**, values change based on applications

**What is the impedance of 250 kVA transformer?**

- impedance of 250 kVA transformer is 2.5%

**What is the impedance of a 1000 kva transformer?**

- For a 1000kVA transformer, the impedance is value is
**6% and not be more than 8%**.

**What is the impedance of a 5 KVA transformer?**

- the impedance of a 5 KVA transformer 4%

**What is the impedance of a 15kva transformer?**

**2.6 %**

That is all about the Three Windings Transformer Per Unit Impedance if you have any further query ask in the comments. Thanks for reading have a nice day