Transformers Flashcards
What does a step up transformer do?
A step-up transformer increases the voltage and decreases the current.
What does a step down transformer do?
a step-down transformer decreases the voltage and increases the current.
What are copper losses?
Copper loss is caused by the direct current (DC) resistance in the primary and secondary windings.
What are iron losses?
Iron loss is subdivided into hysteresis and eddy current losses.
In copper losses, what happens?
When current flows through a conductor, some power is dissipated as heat. The amount of power dissipated is directly proportional to:
The resistance of the wire
The square of the current
How can you minimise copper losses?
A winding’s resistance depends on the diameter of the wire and its length. Copper loss can be minimised by using the proper diameter wire. The large-diameter wire is required for high-current windings. The small-diameter wire is cost-effective for low-current windings.
What are eddy current losses?
Random eddy currents flow through the core, which dissipates power in the form of heat.
What frequencies do transformers work on?
50 or 400 hertz
What is hysteresis loss?
Power transformers normally operate on either 50 Hz or 400 Hz AC. Each tiny domain must realign itself twice during each cycle – a total of 100 times a second when the 50 Hz alternating current is used. Some of the energy used to turn each domain is dissipated as heat within the iron core. This is called hysteresis loss. Hysteresis loss can be minimised by using the appropriate core materials.
What is a transformers voltage to current ratio?
Higher voltage – lower current
Lower voltage – higher current
What factors are involved in a transformers ratio?
The number of turns in the primary and secondary windings.
The voltage across each winding.
The current through the windings.
How can hysteresis loss be reduced?
By using special steel alloys
Which dot combination indicates in phase polarity?
Red dot to red dot
Which dot combination indicates out of phase polarity?
Primary red dot to secondary black dot
