What is a transformer?
is a device used to transfer electrical energy from one electrical circuit to another.
How does transformer operate?
mutual induction. An action by which a change in the current in one conductor induces a voltage in a neighbouring conductor.
What is the purpose used of transformer?
To step voltage up or down.
Minimize line loss and line drop for distribution
For safety and ease of utilization
The transformer winding connected to the load is called the ______________.
What does it do?
secondary winding and it delivers energy
The transformer coil connected to the source of emf is called the ____________.
What is a purpose?
Primary winding, it receives energy.
________ is a measure of a material’s ability to become magnetized
Permeability
What is Reluctance?
Reluctance is the property that opposes magnetic flux or magnetic lines of flux
The amount of magnetism left in a material after the magnetizing force has stopped is called _________
Residual magnetism
In practical transformers, the efficiency with which energy is transferred between the primary and secondary windings falls somewhere in the range ______ to ______
96% to 99%
Transformer maybe classified according to:
- Cooling method
- insulation between the windings
- number of phases
- type of service
- type of winding
What are volts per turn of a transformer with a voltage rating of 480V - 120V if the high-voltage winding contain 200 turns?
2.4 volts per turn?
How is high-voltage winding and low-voltage winding made differently?
High voltage winding is made up of many turns of relatively thin, insulated wire wound around the core.
Low voltage winding is made up with fewer turns, but thicker. The insulation on this winding does not have to withstand the same high stress as the high-voltage
What is the purpose of the core?
The purpose of the core is to concentrate the flux lines so that as much of the flux as possible links with both the primary and secondary coils.
what is the ideal factor that must be considered of the core?
High permeability:
The higher the permeability, the greater the number of flux lines created for a given level of currents.
Low retentivity:
The lower retentivity, the less energy is lost in the form of heat due to hysteresis losses.
High electrical resistance:
the higher the resistance, the less energy is lost in the from of heat due to eddy currents.
Transformers all have the same three basic parts:
- High Voltage winding,
- Low voltage winding,
- Core
What are the three ideal material used in the core has?
- High permeability
- Low retentivity
- High electrical resistance
TRANSFORMER POLARITY
If the X 1 terminal is diagonally across from the H 1 terminal, the
transformer is referred to as having
Additive Polarity
TRANSFORMER POLARITY
If the X 1 terminal is adjacent to the H 1 terminal, the
transformer is referred to as having
Subtractive Polarity
What are the two ways of testing the polarity of transformer leads?
- The DC Kick Test
- The AC Voltmeter Test
What is the reason for laminating the core of a transformer?
To reduce eddy current losses
What are the three conditions that must be met when connecting transformer in parallel?
- The transformers must have the same primary and secondary voltage ratings.
- When making connections, observe the terminal proper polariy of the transformers.
- All the transformers must have the same percent impedance.
The energy losses that occur in transformers may be classified as either core losses or copper losses:
- Core losses are the eddy-current and hysteresis losses in the core.
- Copper losses are the I2R losses in the primary and secondary windings.
Core losses can be measured by performing a test known as the _______________.
Open-circuit test
Copper losses is measured by performing a test called ____________.
Short-Circuit test
