Question

Draw a neat labeled sketch of a three-point starter.

Answer 1

Creating a neat and labeled sketch of a three-point starter is a bit challenging through text alone, but I can describe it in detail for you. A three-point starter is used to control the start of an induction motor, and it includes several key components. Here’s a detailed description of its layout:

1. **Main Components**:
   - **Starter Switch**: This is used to start the motor by allowing current to flow through the motor windings.
   - **No-Volt Release Coil (NVR)**: This component ensures the motor stops if there is a voltage drop or if the supply voltage fails.
   - **Overload Relay**: This protects the motor from overheating by disconnecting it if the current exceeds a preset value.

2. **Basic Layout**:
   - **Power Supply**: Two lines (Live and Neutral) coming from the main power source.
   - **Contactor**: A relay that closes the circuit to start the motor.
   - **Overload Relay**: Connected in series with the contactor.
   - **No-Volt Release Coil**: Connected in parallel with the contactor.
   - **Starting Resistor**: Used to limit the starting current.
   - **Motor**: The load that will be driven by the starter.

### Description of the Sketch:

1. **Power Supply Lines**: Draw two horizontal lines at the top, representing the live (L) and neutral (N) wires coming from the power source.

2. **Starter Switch**:
   - Draw a switch symbol connected to the live line. This is the point where the circuit can be opened or closed to start the motor.

3. **Contactor**:
   - Draw a rectangle (representing the contactor) below the starter switch.
   - Inside the contactor rectangle, include two sets of contacts: one set for the main current path (which connects to the motor) and one set for the control circuit.

4. **Overload Relay**:
   - Draw another rectangle next to the contactor. This relay is in series with the motor’s power path.
   - Label it “Overload Relay”.

5. **No-Volt Release Coil**:
   - Draw a small circle or rectangle near the contactor, connected in parallel with the control circuit of the contactor.
   - Label it “No-Volt Release Coil (NVR)”.

6. **Starting Resistor**:
   - Include a resistor symbol in series with the live line before it reaches the contactor. This is used to limit the starting current.

7. **Motor**:
   - Draw a motor symbol connected to the other side of the contactor, indicating that the power from the contactor flows to the motor.

8. **Connections**:
   - Connect the power supply lines to the starter switch.
   - From the switch, connect to the contactor.
   - From the contactor, connect to the overload relay.
   - From the overload relay, connect to the motor.
   - Draw lines showing the connections between the no-volt release coil and the contactor’s control circuit.

### Labeled Diagram:
- **L** (Live)
- **N** (Neutral)
- **SW** (Starter Switch)
- **C** (Contactor)
- **O/R** (Overload Relay)
- **NVR** (No-Volt Release)
- **R** (Starting Resistor)
- **M** (Motor)

### How It Works:
- When the starter switch is closed, current flows through the starting resistor to the contactor.
- The contactor closes, allowing current to flow directly to the motor.
- The overload relay monitors the motor current and trips if the current exceeds safe limits.
- The no-volt release coil ensures that if the voltage drops or fails, the contactor opens, cutting off power to the motor.

If you need an actual sketch, you might want to look up diagrams online or use diagram-drawing software to create a visual representation based on this description.

Answer 2

A three-point starter is a device used for starting DC motors. It helps in controlling the starting current and protecting the motor from damage during startup. Here is a labeled sketch of a three-point starter:

```
   +-----------------------+
   |                       |
   |       +-----+         |
   |       |     |         |
   |       |  1  |         |
   |       |     |         |
   |       +-----+         |
   |           |           |
   |           |           |
   |           |           |
   |           |           |
   |     +-----|-----+     |
   |     |     |     |     |
   |     |     |     |     |
   |     |     |     |     |
   |     |     |     |     |
   |     |     |     |     |
   |     |     |     |     |
   |     +-----|-----+     |
   |           |           |
   |           |           |
   |           |           |
   |           |           |
   |           |           |
   |           |           |
   |   +-------|-------+   |
   |   |       |       |   |
   |   |   2   |   3   |   |
   |   |       |       |   |
   |   +-------+-------+   |
   |                       |
   |                       |
   |                       |
   +-----------------------+

```

### Labeled Components:

1. **Starting Rheostat**: A variable resistor used to control the starting current. It allows for gradual increase in current as the motor starts. Usually marked as 'Rheostat' or 'R1'.

2. **No-Voltage Release Coil**: This coil is connected to a relay that will automatically disconnect the starter if the voltage falls below a certain level. It's a protective feature to prevent damage due to low voltage. Usually marked as 'NVR Coil' or '2'.

3. **Overload Relay**: This relay protects the motor from overload conditions. If the motor draws excessive current, the relay will trip and disconnect the motor. Usually marked as 'Overload Relay' or '3'.

### Connections:

- **Terminals A and B**: These are connected to the armature and field windings of the DC motor.
- **Terminals 1, 2, 3**: These connect to the power supply, the starting rheostat, and the motor, respectively.

### How It Works:

- When the starter is initially switched on, the rheostat (1) allows a limited amount of current to flow through the motor, thus preventing a high inrush current.
- As the motor starts and picks up speed, the rheostat is gradually adjusted to allow more current to the motor.
- The no-voltage release coil (2) ensures that if there is a power failure or the voltage drops, the starter will disconnect the motor to prevent damage.
- The overload relay (3) monitors the current flowing to the motor and disconnects it if it exceeds the safe operating limit.

If you need a more detailed diagram or additional explanations on specific parts, let me know!