Machine Installation and Types of Enclosures for SS 3

Class: SS 3
Term: First Term
Week: 7
Age: 16 years
Duration: 45 minutes
Subject: Electrical Installation and Maintenance Work
Curriculum Theme: Machine Installation
Previous Lesson: Operation of AC and DC Motors and Generators
Topic: INSTALLATION OF MACHINE
Subject Matter: Types of enclosures; Suitable starter; Installation of A.C and D.C machine; Mounting machine and equipment

Specific Objectives

By the end of the lesson, pupils/students should be able to:

Cognitive Domain

• Identify different types of machine enclosures.
• Explain the purpose and operational principles of suitable motor starters.
• Describe the steps involved in installing AC and DC machines.
• State the importance of proper machine and equipment mounting.

Affective Domain

• Appreciate the importance of safety during machine installation.
• Value the use of correct procedures for electrical machine installation.
• Show interest in learning about various machine enclosures and starters.

Psychomotor Domain

• Demonstrate the connection of a basic motor starter.
• Test for correct rotation of an installed machine.
• Illustrate how to properly mount electrical equipment.

Reference Materials

The following resources were used in planning this lesson:

• 2025 Revised 9 Years Basic Education Curriculum
• Relevant State Unified Scheme of Work
• Electrical Installation and Maintenance Work for Senior Secondary Schools, Book 3
• The HeadTeacher Scheme of work

Instructional Materials

The teacher will teach this lesson with the aid of:

• Various types of motor starters (e.g., Direct-On-Line, Star-Delta)
• Posters showing different machine enclosures
• Diagrams of AC and DC machine connections
• Basic hand tools (screwdrivers, spanners)
• Small AC/DC motor for demonstration (if available)
• Mounting brackets and bolts

Rationale for the Lesson

This lesson is essential for students to understand the practical aspects of installing electrical machines, which is a core skill in electrical installation and maintenance. It helps students grasp the importance of selecting appropriate enclosures for protection and using suitable starters for safe and efficient operation. Proper installation ensures machine longevity, operational safety, and optimal performance in industrial and domestic settings.

Prerequisite/Previous Knowledge

Students should have a basic understanding of electrical safety, types of electrical machines (AC and DC), and fundamental electrical circuits.

Lesson Content/Board Summary

INSTALLATION OF MACHINE

Types of Enclosures

An enclosure protects an electrical machine from environmental factors and provides safety for operators. Different types are designed for specific operating conditions:

1. Open Enclosures: Allow free air circulation but offer minimal protection against dust or moisture.
2. Drip-Proof Enclosures: Designed to prevent falling liquid or dirt from entering the machine.
3. Splash-Proof Enclosures: Protect against splashing liquids or particles from any direction.
4. Totally Enclosed, Non-Ventilated (TENV) Enclosures: Completely sealed to prevent the exchange of air between the inside and outside, relying on the surface area for cooling.
5. Totally Enclosed, Fan-Cooled (TEFC) Enclosures: Similar to TENV but with an external fan to blow air over the motor casing for improved cooling.
6. Explosion-Proof Enclosures: Constructed to withstand an internal explosion of specified gases or vapours and prevent the ignition of external hazardous atmospheres.

Suitable Starters for AC and DC Machines

A starter is an electrical device that controls the starting, stopping, and protection of an electric motor. It limits inrush current during starting and provides overload protection.

For AC Machines (Induction Motors):

1. Direct-On-Line (DOL) Starter: Connects the motor directly to the full supply voltage. Suitable for small to medium-sized motors where the starting current surge is acceptable.
2. Star-Delta Starter: Reduces the starting current by connecting the motor windings in a star configuration during starting, then switching to delta for normal running. Used for medium to large motors.
3. Auto-Transformer Starter: Uses an auto-transformer to reduce the voltage applied to the motor during starting, thereby reducing the starting current. Provides smoother starting than DOL.

For DC Machines:

1. Three-Point Starter: Used for shunt and compound DC motors. It has three terminals: Line (L), Armature (A), and Field (F). It provides protection against overcurrent and loss of field.
2. Four-Point Starter: Similar to a three-point starter but with an additional point for the field winding, making it more stable against variations in field current. Used for larger DC motors or where field current stability is critical.

Installation of AC and DC Machines

The installation process involves several critical steps to ensure safe and efficient operation:

1. Site Preparation: Ensure the installation area is clean, dry, well-ventilated, and free from obstructions.
2. Foundation: Prepare a solid, level foundation capable of supporting the machine’s weight and absorbing vibrations.
3. Positioning: Carefully position the machine on its foundation, ensuring proper alignment with driven equipment (if any).
4. Mounting: Secure the machine firmly to the foundation using appropriate bolts and anti-vibration mounts.
5. Electrical Connections:
   1. Wiring: Connect the power supply cables to the motor terminals according to the wiring diagram. Ensure correct cable sizing and insulation.
   2. Earthing: Properly earth the motor frame to protect against electric shock.
   3. Starter Connection: Connect the motor to its suitable starter, ensuring all control and power circuits are correctly wired.
6. Lubrication: Check and fill lubrication points as per manufacturer’s specifications.
7. Testing:
   1. Insulation Resistance Test: Check the insulation integrity of the motor windings.
   2. Continuity Test: Verify all connections are secure.
   3. No-Load Run: Start the motor without load to check for unusual noises, vibrations, and correct direction of rotation.
   4. Load Test: Gradually apply load and monitor performance parameters.

Mounting Machine and Equipment

Proper mounting is crucial for the stable operation, safety, and longevity of electrical machines and associated equipment.

1. Foundation Bolts: Machines are typically secured to a concrete foundation using anchor bolts embedded in the concrete. This provides a rigid and stable base.
2. Anti-Vibration Mounts: Used to isolate the machine from its surroundings, reducing the transmission of vibrations and noise.
3. Wall/Panel Mounting: Smaller equipment like control panels, starters, and circuit breakers are often mounted on walls or inside enclosures using screws, bolts, or specialized clips.
4. Rack Mounting: Electronic equipment and some control modules are mounted in standardized racks for organized installation and easy access.
5. Considerations for Mounting:
   1. Stability: Ensure the mounting surface is strong enough to support the equipment.
   2. Accessibility: Mount equipment in a way that allows for easy inspection, maintenance, and operation.
   3. Ventilation: Ensure adequate airflow around the equipment to prevent overheating, especially for enclosed motors.
   4. Leveling: Machines should be mounted perfectly level to prevent undue stress on bearings and shafts.

Teaching Methods/Instructional Techniques

Discussion, Demonstration, Guided Practice, Question and Answer, Explanation, Observation, Practical Activity

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Engaging/Reviewing

Teacher’s Activity: The teacher greets the students, reviews the previous lesson on types of electrical machines, and introduces the new topic: “Installation of Machine,” highlighting its importance in practical electrical work.

Pupils’ Activity: Students respond to greetings, recall previous knowledge, and listen attentively to the introduction of the new topic.

Learning Point: Lesson topic introduction

Step 2: Types of Enclosures

Time: 8 minutes

Teaching Skill: Explanation/Illustration

Teacher’s Activity: The teacher explains the concept of machine enclosures and displays posters or actual examples of different enclosure types (e.g., open, drip-proof, totally enclosed, explosion-proof), describing their characteristics and applications.

Pupils’ Activity: Students observe the posters/examples, listen to the explanations, and ask questions for clarification.

Learning Point: Machine enclosure types

Step 3: Suitable Starters

Time: 7 minutes

Teaching Skill: Explanation/Discussion

Teacher’s Activity: The teacher explains the function of motor starters and discusses suitable starters for AC machines (DOL, Star-Delta, Auto-transformer) and DC machines (3-point, 4-point), explaining their operational principles.

Pupils’ Activity: Students listen, take notes, and participate in the discussion by asking questions about starter selection.

Learning Point: Motor starter principles

Step 4: Starter Connections Demonstration

Time: 8 minutes

Teaching Skill: Demonstration/Guided Practice

Teacher’s Activity: The teacher demonstrates the basic connection of a simple DOL starter to a small motor (if available), emphasizing safety procedures and correct wiring sequences. The teacher also explains how to test for correct rotation.

Pupils’ Activity: Students observe the demonstration carefully, noting the connections and safety precautions. They may practice simple connections if materials allow.

Learning Point: Starter connection demonstration

Step 5: Installation of AC and DC Machines

Time: 7 minutes

Teaching Skill: Explanation/Instruction

Teacher’s Activity: The teacher outlines the general steps for installing AC and DC machines, covering site preparation, foundation, positioning, electrical connections (including earthing), lubrication, and initial testing procedures.

Pupils’ Activity: Students listen and take notes on the systematic steps for machine installation.

Learning Point: Machine installation steps

Step 6: Mounting Machines and Equipment

Time: 5 minutes

Teaching Skill: Explanation/Illustration

Teacher’s Activity: The teacher explains the importance of proper mounting and describes different mounting methods (e.g., foundation bolts, anti-vibration mounts, wall mounting), highlighting considerations like stability, accessibility, and ventilation.

Pupils’ Activity: Students listen to the explanation and observe any illustrative materials or diagrams provided.

Learning Point: Equipment mounting methods

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. Mention three types of machine enclosures.
2. What is the main purpose of a motor starter?
3. Name two suitable starters for an AC induction motor.
4. List three important steps when installing an electrical machine.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Machine installation understanding

Step 8: Note-Taking

Time: 4 minutes

Teaching Skill: Guided Writing

Teacher’s Activity: The teacher guides pupils/students to copy the essential Board Summary notes into their notebooks, ensuring key terms and concepts are correctly recorded.

Pupils’ Activity: Pupils/students copy the notes carefully into their notebooks.

Learning Point: Key concepts recorded

Step 9: Conclusion

Time: 1 minute

Teaching Skill: Summarising

Teacher’s Activity: The teacher briefly summarises the lesson, reiterating the importance of correct machine installation, appropriate enclosures, and suitable starters for safety and efficiency.

Pupils’ Activity: Students listen and reflect on the key takeaways from the lesson.

Learning Point: Lesson summary reinforced

Continuous Assessment/Further Study

Type: Homework

Instruction: Answer the following questions in your notebook:

1. Differentiate between a TENV and a TEFC motor enclosure, stating where each might be used.
2. Explain why a Direct-On-Line (DOL) starter is not suitable for very large AC motors.
3. Draw a simple wiring diagram for a 3-point DC motor starter.
4. Research and list five safety precautions to observe during the installation of any electrical machine.

Lesson Keywords

• Enclosure – A casing or housing that protects an electrical machine from its environment.
• Starter – An electrical device used to start, stop, and protect an electric motor.
• AC machine – An electrical machine that operates on alternating current.
• DC machine – An electrical machine that operates on direct current.
• Mounting – The process of securing a machine or equipment to a stable surface or foundation.
• Installation – The process of setting up an electrical machine for operation.

Differentiation

For weaker learners, the teacher will provide simplified diagrams of enclosures and starters, focusing on identifying the main types and their basic functions. They will be given more direct guidance during the starter connection demonstration. Faster learners will be challenged to research specific applications for explosion-proof enclosures or to compare the cost and efficiency of different AC motor starters.

Suggested Lesson Videos

For further understanding, students can search on YouTube for:

• “Types of electric motor enclosures explained”
• “How a DOL starter works”
• “Installation of AC induction motor”

Teacher Guide for Using This Lesson Plan

Before the lesson, ensure you have actual examples of different motor starters (DOL, Star-Delta if possible) and pictorial representations or posters of various machine enclosures. If a small, disused AC or DC motor is available, it would greatly enhance the demonstration of installation and mounting. Emphasize safety throughout the lesson, especially when discussing electrical connections and testing. Begin by reviewing prior knowledge to link it to the new topic. Proceed systematically through the types of enclosures, then suitable starters, followed by the general installation steps and mounting considerations. Encourage students to observe closely during demonstrations and ask questions. Ensure students copy the Board Summary notes accurately during the dedicated note-taking phase. Conclude by reinforcing the critical role of proper installation in electrical engineering.