Exam (elaborations)
Exam (elaborations) Electrical Engineering (Lvl4)
- Institution
- South African College Schools (SACS High)
Exam of 5 pages for the course Electrical Engineering at SACS High (Three phase Q&A)
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ELECTRICAL SYSTEMS & CONSTRUCTIONELECTRICAL ENGINEERING BASICS Q&A
What is the purpose of a circuit diagram?
It shows how a circuit is connected together.
Name 3 types of control diagrams.
Wiring diagram
Schematic diagram
Ladder diagram
Name 3 advantages of proper planning and 3 disadvantages of
poor planning.
Advantages:
You will know exactly what you need to do before you start with
the task
You will not waste time by having to stop working on the task to
get a tool, piece of equipment or component, which you forgot
to buy or collect from the store
You will enjoy doing the task and feel proud that you worked
efficiently
Disadvantages:
Time will be wasted because you have not thought the task
through and you are unprepared
The time taken to complete the task becomes financially
unacceptable for the company
It is seen as a bad advertisement for you and the company
, Name the five main components in the power circuit of a 3-
Phase Direct-on-line-starter
Isolator
Circuit breaker or fuses
Contactor
Overload
Motor
What is the purpose of the five main components in the power
circuit?
Isolator:
To separate an installation from all sources of electrical energy
Circuit breaker or fuses:
Back-up-protection (Short circuit protection) To avoid
equipment damage, any short circuit protection device must be
capable of detecting and quickly breaking any high levels of
fault current, before they reach their peak value
Contactor:
To make and break the circuit. Solenoid (coil) inside contactor.
When current is passed through it, it creates a magnetic field to
operate the plunger. Also acts as a No-volt coil. When voltage
drop lower than 70% of supply the contactor drops out to
protect the motor against lower voltage
Overload:
Protects the circuit against overload current (over current is a
circuit that is sound). It also protects the circuit against single-
phasing
Motor:
Change electrical energy to mechanical energy
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