WorksheetsTransformers Revision Week 3
Total questions: 12
Worksheet time: 3600secs
Why are transformer windings submerged in transformer oil?
It is a good conductor of electricity
It is cheap and readily available
It is environmentally friendly and easily recyclable
Insulation and cooling
Aside from current and voltage information, what else can be found on a Transformer nameplate?
(multiple correct answers)
%Z
% Impedance
Frequency
Power Factor
VA Rating
Physical Dimensions in mm
All of these transformer cores are referred to as:
Shell type
Toroidal type
Core type
Which of the following is a common use for transformers?
Heating water in a kettle
Stepping up voltage for long-distance power transmission
Generating electricity from wind turbines
Cooling electronic devices
How does using a silicon steel core reduce losses in transformers?
By increasing the resistance in the core
By decreasing the magnetic permeability of the core
By increasing the coercivity of the core material, reducing the area enclosed by the hysteresis loop
By decreasing the area enclosed by the hysteresis loop in the core material
How do laminations in the core of a transformer reduce eddy currents?
By increasing the magnetic permeability of the core
By decreasing the thickness of the core
By providing a path of higher resistance, reducing circulating currents in the core
What are transformers rated in?
Apparent Power (VA)
Reactive Power (VAr)
True Power (W)
Doesn't matter
What is a key characteristic of an autotransformer?
It has only one winding
It is used exclusively in high-voltage transmission
It is less efficient than traditional transformers
It cannot step up or step down voltage
What safety feature do current transformers (CTs) commonly include to protect against high currents?
Built-in fuse
Overload relay
Magnetic core
Secondary shorting block
The transformer in the image adjacent has 2000 turns on its primary winding and 12000 turns on its secondary winding. The primary is connected to 11kV supply. What is the voltage output on the secondary winding?
(Answer with units and no spaces)
(a)
Which of the following factors determine the magnitude of induced electromotive force (EMF) in a transformer? (multiple answers are correct)
The number of turns in the each coil
Maximum value of magnetic flux
Frequency of the applied voltage
Resistance of the winding
A transformer has a full load current of 300A and a prospective short circuit current of 6000A. What is the percentage impedance of the transformer?
(a)
