Download Basic circuit power point

BASIC ELECTRICAL
CIRCUITRY & APPLICATIONS
Aims:
To explore different wiring methods for lighting and
power circuits.
Outcomes:
•State
the different parts of an electrical circuit
•Draw different lighting circuits
•Draw a ring final socket circuit
Component parts of an electrical
circuit.
The BS7671 defines a circuit as ‘an assembly of electrical
equipment supplied from the same origin and protected against
overcurrent by the same protective devices’.
Here is a list of components that make up an electrical circuit:
• Source of supply
• Circuit conductors (cable)
• Circuit protection
• Circuit control
• Load
Source of supply:
For current to flow two conditions have to be met.
1. There has to be a potential difference applied
across the circuit. (voltage)
2. There has to be a complete circuit (circle) for
current to flow around.
There are two types of supply. What are they?
A.C voltage and D.C voltage.
For an a.c. supply, either an a.c. generator or d.c. generator with
components to rectify the supply, can be used.
If a d.c. supply is required, then this is derived from a battery.
The size and type of voltage required for the supply is determined
by the load equipment being used. A plate will usually be attached
to the equipment indicating its safe working voltage and other
requirements.
Circuit conductors:
The circuit conductors are those parts of the circuit that the current
passes through. These are the cables. There are two parts to a
cable. One is the conductor itself. This is usually made from copper.
The other is the insulation, usually made from PVC, which forms a
sheath around the conductor. The insulation is required to:
• Prevent the conductors touching together; this could short the
circuit and stop it from working.
• Prevent users of the circuit from coming into contact with the
conductors and receiving an electric shock.
The type of insulation required is determined by the voltage which is
to be applied to the cable.
Circuit protection:
Every circuit requires protection if, in the event of a fault, damage is to be
avoided. This is usually by the way of a suitably rated fuse or protective
device. Such a device is called a miniature circuit breaker (MCB). This will
protect both the load and the cables supplying the load, from the heat
damage associated with large fault current.
There are various sizes and types of fuses, which include:
• BS 3036 rewirable fuses
• BS 1361 cartridge fuses
• BS EN 60898 MCB’s
• BS EN 61009 RCBO’s
Circuit control:
It is important that a circuit, no matter its level of complexity, can be
controlled.
This could be either:
• A simple switch, allowing you to turn the circuit on or off
• A time switch, which activates the circuit at certain times
Can you think of any thing you may use in everyday life that can
be thought of as a switch?
Load:
The load refers to the item that requires the supply in order to function.
This could be the lights in a circuit, a heater, a motor to drive a pump or
any item of equipment (or combinations) that require an electrical supply
in order for them to work.
Electrical loads are rated in watts or kilowatts (W and kW). The size of the
load is generally stamped on the equipment or marked on a name plate.
On the plate it should state:
•
•
•
•
Rating in watts
Frequency of the supply
Supply voltage
Full load current
If this information is not available on the plate, then will need to contact
the manufacturer.
Basic lighting circuit
diagram
One way lighting circuit
Below is a diagram of a one way lighting circuit using the “loop in”
method. This is sometimes called the “3 plate” method.
The “loop in” method is done by
taking the supply cable to the lighting
point (ceiling rose). From here a
switch cable is taken to the switch
plate. Then the supply cable
continues from the lighting point to
the next lighting point and so on till it
finishes at the last light on the circuit.
This method can also be done using
a junction box.
Two way lighting circuit
Here is a lighting circuit that is controlled
by two switch’s. Again this is
the “loop in” or “3 plate”
method of wiring.
You would normally use two way
lighting circuits on hall ways
and landings.
Two way & intermediate lighting circuit
Two way & intermediate lighting circuits would be used where there is more
than two floors i.e. a three storey house.
Sockets circuits
There a two types of sockets circuits.
• Ring final circuits
• Radial circuit
Basically the ring final circuit (RFC) starts at the consumer unit, goes to
each socket, than back to the consumer unit (like a ring).
A radial circuit, starts at the consumer unit, goes to each socket and
finishes at the last socket on the circuit. It can also branch off from each
socket to numerous sockets (like a tree branch).
Ring final circuit (RFC)
Below is a diagram of a ring final socket circuit. You can add
a spur from each socket or junction box but only once.
Radial circuit
Here we have a diagram of radial socket circuit.
Radial circuits are
also used for a
number of different
applications. Can
you think of any you
may have seen or
even use in
everyday life?