Electrical Transformer Definition:
Electrical Power Transformer is a static device which transforms electrical energy from one circuit to another without any direct electrical connection and with the help of mutual induction between two winding’s. It transforms power from one circuit to another without changing its frequency but may be in different voltage level.
Types Transformer:
- According to operation:
- Step up Transformer
- Step down Transformer
- One to One Transformer
- Same Ratio Transformer
- According to Construction of core:
- Core type Transformer
- Sell type Transformer
- Spiral core type Transformer
- According to Cooling System:
- Natural Cooled Transformer
- Air Cooled Transformer
- Oil Cooled Transformer ( Self cooled & water cooled).
- According to Apply System:
- Power Transformer
- Distribution Transformer
- Auto Transformer
- Instrument Transformer ( Current Transformer & Potential Transformer).
- According to Set up System:
- Indoor type Transformer
- Outdoor type Transformer
- Pole mounted type Transformer
- According to Frequency:
- Audio Frequency Transformer
- Radio Frequency Transformer [13].
Faraday’s Laws:
Any change in the magnetic field of a coil of wire will cause an emf to be induced in the coil. This emf induced is called induced emf and if the conductor circuit is closed, the current will also circulate through the circuit and this current is called induced current.
Method to change magnetic field:
1. By moving a magnet towards or away from the coil
- By moving the coil into or out of the magnetic field.
- By changing the area of a coil placed in the magnetic field
- By rotating the coil relative to the magnet.
Faraday’s Second Law:
It states that the magnitude of emf induced in the coil is equal to the rate of change of flux that linkages with the coil. The flux linkage of the coil is the product of number of turns in the coil and flux associated with the coil.
These laws are called Faraday’s laws of electromagnetic induction.
Technical Specification of Transformers:
A transformer is an electrical device designed to transfer electrical energy between two or more circuits through electromagnetic induction. Its key technical specifications include the rated power (measured in VA or kVA), primary and secondary voltage ratings (in volts), frequency (typically 50Hz or 60Hz), impedance (measured in ohms), and efficiency. Transformers also have a specific phase configuration (single-phase or three-phase), a core material (usually silicon steel or amorphous steel), and insulation class, which determines the maximum operating temperature. The turns ratio between primary and secondary windings is crucial for voltage transformation, and the voltage regulation indicates the change in secondary voltage under varying load conditions.
Technical Specification of main Transformers:
| Equipment’s Name | Main Transformer No.1 | Main Transformer No.2 |
| Type | SFPZ-156300-230TH | SFPZ-156300-230TH |
| Capacity (KVA) | 94000/156300 | 94000/156300 |
| Rated voltage(KV) | 245±9X1.25%/13.8 | 245±9X1.25%/13.8 |
| Rated Current(A) | 368.3 | 368.3 |
| Voltage Regulation Mode | On Load Regulation | On Load Regulation |
| Cooling mode | ONAN/OFAF | ONAN/OFAF |
| Connection Moode | Y/Δ-11 | Y/Δ-11 |
| Phase | 3 | 3 |
| Frequency(Hz) | 50 | 50 |
| Impedance Voltage | Ud 14% | Ud 14% |
| Upper Layer oil temp. rise(K) | 50 | 50 |
| Winding Average temp. rise (K) | 60/90 °C | 60/90 °C |
Table: Technical Specification of main Transformer of a power station.
Technical Specification of Unit Auxiliary Transformers:
| Equipment’s Name | Unit Auxiliary Transformer No.1 | Unit Auxiliary Transformer No.2 |
| Type | S-20000/13.8 | S-20000/13.8 |
| Capacity (KVA) | 20000 | 20000 |
| Rated voltage(KV) | 13.8±2X2.5%/6.9 | 13.8±2X2.5%/6.9 |
| Rated Current(A) | 836.7/1673.5 | 836.7/1673.5 |
| Voltage Regulation Mode | Zero Load Regulation | Zero Load Regulation |
| Cooling mode | ONAN | ONAN |
| Connection Moode | Δ-1/Y | Δ-1/Y |
| Phase | 3 | 3 |
| Frequency(Hz) | 50 | 50 |
| Impedance Voltage | Â 10.5% | Â 10.5% |
| Upper Layer oil temp. rise(K) | 50 | 50 |
| Winding Average temp. rise (K) | 60 | 60 |
Table: Technical Specification of Unit Auxiliary Transformer of a power station.
11.6 Technical Specification of Standby Transformers:
| Equipment’s Name | Start-up/ Standby Transformer | Construction Standby Transformer | Excitation Transformer |
| Type | SZ-20000/220 | SB-20000/52Th | ZSCB9-1500/13.8 |
| Capacity (KVA) | 20000 | 2000 | 1500 |
| Rated voltage(KV) | 230±9X1.25%/6.9 | 32±2X2.5%/6.9 | 13.8±2X2.5%/0.5 |
| Rated Current(A) | 50.2/1673.5 | 56.1/1673.3 | 62.8/1732 |
| Voltage Regulation Mode | On Load Regulation | Zero Load Regulation | Zero Load Regulation |
| Cooling mode | ONAN | ONAN | ANAF |
| Connection Moode | Y/Y-12 | Δ/Y-1 | Y/ Δ-5 |
| Phase | 3 | 3 | 3 |
| Frequency(Hz) | 50 | 50 | 50 |
| Impedance Voltage | 10.5% | Â 6% | 6.14% |
| Upper Layer oil temp. rise(K) | 50 | 50 | ———- |
| Winding Average temp. rise (K) | 60 | 60 | 100 |
Table: Technical Specification of Standby Transformers of a power station.
