This entails a quick Question & Answer summary of what Drafting and design course is all about in electrical engineering. As a student who’s interested in Drafting and design course, it’s advisable you go through this.
1. List three(3) types of connection diagram in an electrical design
- Block diagram
- Wiring diagram
- Schematic diagram
Write short note on each types of connection diagram
- Block diagram: is a symbolic representation of a working process, production line or even it can be used to represent a system of government activities.
- Schematic diagram: it is a standard name used for a circuit diagram. It can be defined as a diagram that utilizes a circuit symbol to show the interconnection and function of a component that makes up of a circuit diagram of a system.
- A wiring diagram: shows the relative layout of the components and the wire connections between them. This type of diagram shows the physical relation of all devices in the system, the conductor terminations between these devices, and are commonly used in motor control installations
B. state four(4) classification of lighting scheme
- Direct lighting scheme
- Indirect lighting scheme
- Semi-direct lighting scheme
- Semi-indirect lighting scheme
- Direct lighting schemes: By this method most of the lighting scheme is made available on the working surface and very few percent is wasted. Light shining onto an object is called direct lighting. It determines the color and quantity of light that reaches a surface from a light source, but ignores all light that may arrive at the surface from any other sources, such as after reflection or refraction.
- Indirect lighting scheme: The light does not reach the working surface directly. Uses one or more fixtures to aim light onto the ceiling and upper walls, which act as reflectors and distribute the light evenly throughout the room. Indirect lighting is a form of ambient lighting.
- Semi-direct lighting scheme: In this scheme about 60 to 90% of total light flux is made to fall on the working surface and 10 to 40% is allowed to fall on the ceilings and walls. This is achieved by providing semi-direct reflectors. Such a scheme is best suited to rooms having bigger height
- Semi-indirect lighting scheme: In this system 60 to 90% of the total light flux is diverted to fall on the ceiling from where the light is directed on the working surface by diffused reflection. Only 30 to 40% flux reaches the working surface.
C. Write short notes on each of the following; cosine law, inverse square law, maintenance factor and diversity factor.
- Cosine law: the illumination on the surface is proportional to the cosine of the angle X between the direction of the incident light and the normal to the surface.
- Inverse square law: this illumination at a point for the surface produced by light from the point of source was inversely to the square of the point of source.
- Maintenance factor: it refers to the loss of light that occurs over time and is also known as loss factor. During the operating time of light sources, it can be seen as slight decrease of light output. in other words it is called lumen
- Diversity factor: this is the ratio of the sum of individual demand of the various sub-division of the system to the maximum demand of the whole system under consideration.
2. Enumerate the difference between switch gear and distribution switch board
Switch gear
- Switch gears protect equipment from electrical hazards or failure due to short circuit.
- Switch gear finds their use in powering transformers lines, generators and power networks.
- Switch gears is designed to handle voltages that can reach 350KV.
- Switch gears come with automatic features and come with manual control during emergency.
- Switch gear has switching device that are required for low to medium-voltage circuits.
Switch board
- They are designed to handle lower voltages that are generally less than 60 volts
- Switch boards don’t have any automatic features and are placed to display the amount of power consumed by individual circuits.
- They consists of panel where switches, buses and electrical control devices have been mounted on the front or back end
- They are only used to distribute power to multiple sources and transmit them to individual loads, transformers, panel boards and control equipment.
- They have fixed mount circuit breakers that are connected directly to bus bar.
B. State four(4) factors to be considered when selecting a consumer unit for an installation.
- Number of circuits
- Type of circuits
- Brand and model
- Price
C. Explain briefly the difference between domestic premises and non-domestic premises and state the types of supplies which are taken to each of the premises stated above
Domestic premises are residential wiring that run through walls in a single phase design and it uses less voltage due to lower electrical load.
Non-domestic premises are industrial wiring that uses a three-phase design to create higher output to power higher voltage equipment and multiple systems.
Note: Domestic premises make use of 230/240V while non-domestic premises make use of 11/33KV
3. Explain briefly the term stroboscopic effect on rotating electrical equipment.
Stroboscopic effect is the phenomenon which makes moving objects like fan blades to appear to be stand still and a wave of the hand to appear as if it occured in a series of jump.
State two(2) methods to be adopted so as to reduce stroboscopic effect
- Using three lambs on the separate phase of 3-phase supply: when three(3) phase supply is used in the industry the adjacent fluorescent lamps should be fed with different phases so that the zero crossing of the two lambs will not be the same.
- Reducing the level of TLMs: design of lighting equipment to reduce the TLMs of the light sources is typically a trade off for other product properties and generally increases cost and size, shortens lifetime or lower energy efficiency.
