Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Winding Drawing
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Winding Drawing
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Electrical Installation And Maintenance Work
Class: Senior Secondary 3
Term: 2nd Term
Week: 4
Theme: Workshop Practices
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
A winding drawing is a schematic representation of the electrical connections within the armature of a DC machine. It illustrates how the individual coils are connected to each other and to the commutator segments, and often indicates their position relative to the magnetic poles. These drawings are vital for understanding the operational principles of DC machines, for manufacturing windings, and for troubleshooting and repairing faulty machines.
In lap winding, the ends of each armature coil are connected to adjacent commutator segments. This creates a winding where the coils "lap" back on themselves.
Characteristics of Lap Winding: Coil Connection: The end of one coil is connected to a commutator segment, and the start of the next coil (which is typically adjacent to the first) is connected to the next commutator segment, creating a "lap" arrangement.
Parallel Paths (A): The number of parallel paths for current flow in a lap winding is equal to the number of poles (P) of the machine. So, A =
P. Brushes: The number of brushes required is equal to the number of poles.
Current and Voltage: Lap windings are suitable for machines requiring high current and low voltage. This is because having more parallel paths reduces the equivalent resistance of the armature, allowing more current to flow without excessive voltage drop. Commutator Pitch ($Y_c$): For lap winding, $Y_c = \pm 1$. This means the coil ends connect to adjacent segments.
Drawing Principle: The winding progresses around the armature and "laps" back, connecting to adjacent commutator segments. The resultant pitch is usually small.
Applications in Nigeria: DC welding generators (require high current for welding arcs). Low-voltage, high-current generators for electroplating. Automobile starter motors (need high starting current). Small-scale power generation units (e.g., diesel generators used in local workshops or small businesses for specific high-current loads).
Steps for Drawing a Simple Lap Winding:
1. Determine Parameters: Identify the number of poles (P), number of commutator segments (C), and number of armature slots (S). For simplicity, assume 1 coil per slot. So, number of coils (N) = S.
2. Draw Commutator: Represent the commutator segments as a series of rectangular blocks at the bottom of the diagram, numbered consecutively (e.g., 1, 2, 3...).
3. Draw Coils: Represent each coil with two coil sides (often shown as vertical lines representing conductors in slots) and connections at the front and back ends. The front end connects to the commutator, and the back end connects to another coil side.
4. Connect Front Ends: Connect the ends of each coil to adjacent commutator segments. For instance, if coil 1 starts at segment 1, its other end will connect to segment 2.
5. Connect Back Ends (Armature Winding): The back end connection is crucial. For lap winding, the finishing end of one coil connects to a commutator segment, and the starting end of the next coil connects to the next adjacent commutator segment. The winding progresses by connecting the end of one coil to an adjacent commutator segment and then to the start of the next coil, which effectively laps back under the original poles.
Rule of thumb for drawing: Start a coil from segment
1. Its two sides are placed in slots, say slot 1 and slot 3 (spanning a pole pitch). The end of this coil is connected to segment
2. From segment 2, the next coil starts, and its sides are in slot 2 and slot 4, and its end connects to segment 3, and so on.
6. Indicate Direction: Use arrows to show the direction of current flow through the coils.
7. Identify Brushes: Indicate the positions of brushes, usually placed at points of maximum current collection/supply (under the interpolar axis). In lap winding, there are P brushes. Example Illustration for Lap Winding (Simplified - 2 poles, 4 coils, 4 segments): Commutator segments: C1, C2, C3, C4 Coils: Coil A, Coil B, Coil C, Coil D (each with two sides)
Poles: N, S Drawing:
1. Draw C1, C2, C3, C4.
2. Coil A: Start C1, Sides A1 (slot 1) & A2 (slot 3). End C2.
3. Coil B: Start C2, Sides B1 (slot 2) & B2 (slot 4). End C3.
4. Coil C: Start C3, Sides C1 (slot 3) & C2 (slot 1, under next pole). End C4. (
Note: A2 and C1 are in the same slot but different layers).
5. Coil D: Start C4, Sides D1 (slot 4) & D2 (slot 2, under next pole). End C1. (
Note: B2 and D1 are in S Drawing:
1. Draw C1, C2, C3, C4.
2. Coil A: Start C1, Sides A1 (slot 1) & A2 (slot 3). End C2.
3. Coil B: Start C2, Sides B1 (slot 2) & B2 (slot 4). End C3.
4. Coil C: Start C3, Sides C1 (slot 3) & C2 (slot 1, under next pole). End C4. (
Note: A2 and C1 are in the same slot but different layers).
5. Coil D: Start C4, Sides D1 (slot 4) & D2 (slot 2, under next pole). End C1. (
Note: B2 and D1 are in same slot but different layers). This creates a continuous, closed winding. The connections effectively "lap" back on themselves around the commutator. In wave winding, the ends of each armature coil are connected to commutator segments that are approximately two pole pitches apart, bypassing several intermediate segments. This creates a winding that progresses in a continuous "wave" around the armature.
Characteristics of Wave Winding: Coil Connection: The end of one coil is connected to a commutator segment, and the start of the next coil is connected to a segment that is far removed from the first, creating a wave-like progression.
Parallel Paths (A): The number of parallel paths for current flow in a wave winding is always 2, regardless of the number of poles (P). So, A =
2. Brushes: Only two brushes are theoretically required, though more can be used for better current collection.
Current and Voltage: Wave windings are suitable for machines requiring low current and high voltage. With only two parallel paths, the equivalent resistance is higher, leading to a higher voltage for a given current. Commutator Pitch ($Y_c$): For wave winding, $Y_c = (C \pm 1) / (P/2)$, where C is number of commutator segments and P is number of poles. $Y_c$ is approximately $2C/P$.
Drawing Principle: The winding does not "lap" back but rather "waves" forward, connecting widely spaced commutator segments.
Applications in Nigeria: Small DC motors (e.g., in domestic appliances, fans, toys). DC generators for lighting (need higher voltage, lower current). Exciter generators for larger AC alternators (provide field excitation at higher voltage). Small-scale renewable energy systems (e.g., micro-hydro generators, wind turbine generators) where higher voltage output is desired for transmission over short distances.
Steps for Drawing a Simple Wave Winding: Determine Parameters: Identify P, C, S. Ensure C is such that a proper wave winding can be formed (e.g., for simple wave winding, $C \pm 1$ must be divisible by P/2).
Draw Commutator: Represent the commutator segments as for lap winding.
Draw Coils: Represent each coil with two coil sides and connections.
Connect Front Ends: The key difference is how the coils connect to the commutator. For wave winding, the end of one coil connects to a commutator segment that is approximately $Y_c$ (commutator pitch) segments away from the start of the previous coil.
Rule of thumb for drawing: Start a coil from segment
1. Its two sides are in slots, say slot 1 and slot 3 (spanning a pole pitch). The end of this coil connects to a segment that is $Y_c$ segments away from the starting segment of the next coil. The winding continues in this manner, connecting the end of a coil to a segment "far away" from the start of the previous coil, creating a continuous "wave" that traverses the entire commutator before returning to the initial segment.
Connect Back Ends (Armature Winding): Similar to lap winding, the back end connects coil sides.
Indicate Direction: Use arrows for current flow.
Identify Brushes: Usually, two brushes are sufficient for wave windings, positioned for maximum current collection. Example Illustration for Wave Winding (Simplified - 2 poles, 3 coils, 3 segments): Commutator segments: C1, C2, C3 Coils: Coil A, Coil B, Coil C Poles: N, S Commutator Pitch ($Y_c$): Assume $Y_c = (C \pm 1) / (P/2) = (3+1) / (2/2) = 4$. This is a simplified representation, typically, $Y_c$ would connect to a segment that is $C/P$ segments apart. For a simple visual, let's assume it jumps.
Drawing (simplified): Draw C1, C2, C
3. Coil A: Start C1, Sides A1 (slot 1) & A2 (slot 3). End C3. (Jumps from C1 to C3)
Coil B: Start C3, Sides B1 (slot 2) & B2 (slot 4). End C2. (Jumps from C3 to C2)
Coil C: Start C2, Sides C1 (slot 3) & C2 (slot 1). End C1. (Jumps from C2 to C1) This creates a "wave" where the winding travels across the armature before completing a loop.
Materials: Whiteboard/Chalkboard, markers/chalk, large sheets of paper (flip chart), rulers, pencils, prepared diagrams of simple lap and wave windings (can be drawn on cardboard or projected), sample damaged armature (if available).
Teacher Activities: Introduction (10 min): Begin by showing pictures or real examples of DC motors/generators (e.g., car starter motor, Keke Napep generator, small drilling machine motor). Explain that inside these machines, there are wires (windings) arranged in specific ways to make them work. Introduce "Winding Drawing" as the electrical blueprint for these arrangements. State the learning objectives for the lesson. Key Concept Explanation & Discussion (20 min): Define armature, coil, commutator, pole, brush, and winding pitches using simple language and analogies. Clearly differentiate between lap and wave windings based on their coil connection patterns (adjacent vs. widely spaced commutator segments). Use a simplified diagram to illustrate this fundamental difference. Discuss the impact of each winding type on current and voltage characteristics and their suitability for different applications.
Demonstration: Drawing Lap Winding (20 min): Using a large drawing surface, demonstrate step-by-step how to draw a simple lap winding. Use a concrete, easy-to-follow example (e.g., 2-pole, 4-coil, 4-segment lap winding).
Explain each step: drawing commutator segments, representing coils, connecting front ends to adjacent segments, and showing the "lap" progression. Emphasize using a ruler for neatness and clear labeling.
Demonstration: Drawing Wave Winding (20 min): Follow a similar step-by-step demonstration for a simple wave winding (e.g., 2-pole, 3-coil, 3-segment wave winding).
Highlight the key difference: the "jump" in commutator connections for wave winding. Stress the importance of understanding the commutator pitch ($Y_c$) for wave windings.
Interpretation Practice (15 min): Project or display pre-drawn simple diagrams (one lap, one wave). Guide students to identify each type, explain why, and state its likely application.
Ask probing questions: "What tells you this is a lap/wave winding?", "What kind of machine would use this?", "How many parallel paths do you see?" Q&A Session (5 min): Address any immediate questions or misconceptions.
Student Activities: Active Listening & Note-Taking: Students listen attentively and take notes during the teacher's explanations and demonstrations.
Participation in Discussions: Students respond to questions, share observations, and ask clarifying questions during the interpretation practice.
Observation of Demonstrations: Students closely observe the teacher's drawing demonstrations, paying attention to the step-by-step process.
Guided Drawing (following next section): Under teacher guidance, students attempt to draw simple lap and wave windings on their own. Interpreting Drawings (following next section): Students analyze sample winding drawings to identify their type and characteristics.
Generator and Motor Repairs in Local Workshops: Many informal and formal electrical repair shops across Nigeria (e.g., along Ladipo market in Lagos, Ariaria market in Aba) routinely repair and rewind DC motors and generators. Understanding winding drawings is crucial for identifying existing winding types, troubleshooting faults, and correctly rewinding armatures, ensuring the repaired equipment functions as intended. This directly impacts the lifespan and reliability of machinery used by small businesses and households. Rural Electrification Projects and Renewable Energy Systems: In areas relying on small-scale DC generators (e.g., from solar, wind, or micro-hydro systems), knowing the characteristics of lap versus wave windings helps technicians select or design generators optimized for specific load requirements. For example, a generator for powering a village's lighting system might require a high-voltage wave winding, while one for charging multiple batteries simultaneously might benefit from a high-current lap winding. This ensures efficient power delivery in off-grid communities.
Appliance and Vehicle Maintenance: Many common appliances (e.g., blenders, drills) and vehicles (e.g., Keke Napep, cars) in Nigeria use DC motors. Faults in these motors often relate to winding issues. Knowledge of winding drawings helps technicians understand the internal connections, identify burnouts or short circuits, and correctly carry out repairs, thus contributing to the local economy by extending the life of these essential items and reducing reliance on imports.