Explain with the help of a neat diagram the following methods of speed control for a DC series motor: (i) Field diverter method. (ii) Tapped field method.
2 Answers
Certainly! Let's dive into the speed control methods for a DC series motor with detailed explanations and diagrams.
### 1. Field Diverter Method
**Concept:**
In a DC series motor, the field windings and the armature are connected in series. This means the same current flows through both the field and armature windings. The speed of the motor is inversely proportional to the field flux. By diverting a part of the current away from the field winding, we effectively reduce the field flux, which increases the motor speed.
**Diagram:**
```
+V
|
|
[Field Diverter]
| +-------+
| | |
[Field] [Motor] |
| | |
+-------+ |
| |
[Armature] [Load]
| |
+---------------+
```
**Explanation:**
- **Field Diverter:** This is a resistor or a set of resistors connected in parallel with the field winding.
- **Operation:** When the diverter is used, part of the current bypasses the field winding, reducing the total field current. As the field current decreases, the magnetic flux produced by the field winding reduces, leading to an increase in speed.
**Speed Control:**
- **Increasing Speed:** To increase the speed, the field diverter resistance is increased, allowing more current to bypass the field winding, thus reducing the flux.
- **Decreasing Speed:** To decrease the speed, the field diverter resistance is decreased, allowing more current to flow through the field winding, increasing the flux.
### 2. Tapped Field Method
**Concept:**
The tapped field method involves varying the number of turns in the field winding. By tapping different points on the field winding, you effectively change the field strength and, consequently, the speed of the motor.
**Diagram:**
```
+V
|
|
[Tap 1]
|
[Field]
|
[Tap 2]
|
[Motor]
|
|
[Armature]
|
+-------+
| |
[Load] |
| |
+-------+
```
**Explanation:**
- **Tapped Field Winding:** The field winding is wound in sections, and taps are provided at various points.
- **Operation:** By selecting different taps, you can change the number of effective turns in the field winding. This changes the field current and, hence, the field flux.
**Speed Control:**
- **Increasing Speed:** By tapping at a point closer to the end of the winding, you use fewer turns, resulting in lower field flux and higher speed.
- **Decreasing Speed:** By tapping at a point closer to the start of the winding, you use more turns, resulting in higher field flux and lower speed.
### Summary
- **Field Diverter Method:** This involves adding a parallel resistor to the field winding to divert part of the current, thereby controlling the flux and speed.
- **Tapped Field Method:** This involves using different taps on the field winding to vary the number of turns in use, thereby controlling the flux and speed.
Both methods achieve speed control by altering the field flux, but they do so in different ways—one by diverting current and the other by changing the winding turns.
### 1. Field Diverter Method
**Concept:**
In a DC series motor, the field windings and the armature are connected in series. This means the same current flows through both the field and armature windings. The speed of the motor is inversely proportional to the field flux. By diverting a part of the current away from the field winding, we effectively reduce the field flux, which increases the motor speed.
**Diagram:**
```
+V
|
|
[Field Diverter]
| +-------+
| | |
[Field] [Motor] |
| | |
+-------+ |
| |
[Armature] [Load]
| |
+---------------+
```
**Explanation:**
- **Field Diverter:** This is a resistor or a set of resistors connected in parallel with the field winding.
- **Operation:** When the diverter is used, part of the current bypasses the field winding, reducing the total field current. As the field current decreases, the magnetic flux produced by the field winding reduces, leading to an increase in speed.
**Speed Control:**
- **Increasing Speed:** To increase the speed, the field diverter resistance is increased, allowing more current to bypass the field winding, thus reducing the flux.
- **Decreasing Speed:** To decrease the speed, the field diverter resistance is decreased, allowing more current to flow through the field winding, increasing the flux.
### 2. Tapped Field Method
**Concept:**
The tapped field method involves varying the number of turns in the field winding. By tapping different points on the field winding, you effectively change the field strength and, consequently, the speed of the motor.
**Diagram:**
```
+V
|
|
[Tap 1]
|
[Field]
|
[Tap 2]
|
[Motor]
|
|
[Armature]
|
+-------+
| |
[Load] |
| |
+-------+
```
**Explanation:**
- **Tapped Field Winding:** The field winding is wound in sections, and taps are provided at various points.
- **Operation:** By selecting different taps, you can change the number of effective turns in the field winding. This changes the field current and, hence, the field flux.
**Speed Control:**
- **Increasing Speed:** By tapping at a point closer to the end of the winding, you use fewer turns, resulting in lower field flux and higher speed.
- **Decreasing Speed:** By tapping at a point closer to the start of the winding, you use more turns, resulting in higher field flux and lower speed.
### Summary
- **Field Diverter Method:** This involves adding a parallel resistor to the field winding to divert part of the current, thereby controlling the flux and speed.
- **Tapped Field Method:** This involves using different taps on the field winding to vary the number of turns in use, thereby controlling the flux and speed.
Both methods achieve speed control by altering the field flux, but they do so in different ways—one by diverting current and the other by changing the winding turns.
Sure, let's explore the methods of speed control for a DC series motor: the Field Diverter Method and the Tapped Field Method. I'll provide detailed explanations and diagrams to clarify these concepts.
### 1. Field Diverter Method
**Description:**
In a DC series motor, the field windings and the armature windings are connected in series. The speed of the motor is inversely proportional to the field flux (since the field flux is constant for a given current), and the field flux can be controlled by altering the current through the field winding.
**Method:**
In the Field Diverter Method, a diverter (or shunt resistor) is connected in parallel with the field winding. This diverter allows a portion of the current to bypass the field winding, thereby reducing the effective field current and hence the field flux.
**Diagram:**
```
+V
|
|
| +---------+ +---------+
| | | | |
| | Field | | Diverter|
| | Winding | | (Resistor)|
| | | | |
| +----||----+ +----||----+
| | |
| | |
| | |
| | |
| +------------+
| Armature
| Winding
| |
| |
| |
| ---
| -----
|
|
|
-
```
**Explanation:**
- **Field Winding:** Connected in series with the armature winding.
- **Diverter:** A resistor connected in parallel with the field winding.
- **Effect:** By adjusting the resistance of the diverter, you can control the amount of current bypassing the field winding. This reduces the overall field flux, which increases the speed of the motor.
**Operation:**
1. **Diverter Closed:** When the diverter resistance is very low, most of the current flows through the diverter, reducing the field current and hence the flux. This increases the speed.
2. **Diverter Open:** When the diverter is disconnected or has a high resistance, more current flows through the field winding, increasing the flux and thus reducing the speed.
### 2. Tapped Field Method
**Description:**
The Tapped Field Method involves providing multiple taps (connections) on the field winding. By selecting different taps, you change the effective number of turns in the field winding, thus varying the field flux.
**Method:**
In this method, the field winding is designed with several taps, and a switch or selector is used to connect the field winding to different taps. Each tap represents a different number of turns of the winding, altering the field flux.
**Diagram:**
```
+V
|
|
| +--------+--------+--------+--------+
| | Tap 1 | Tap 2 | Tap 3 | Tap 4 |
| | | | | |
| +----||----+----||----+----||----+----||
| | | | |
| | | | |
| | | | |
| | | | |
| Armature Winding
| |
| |
| |
| ---
| -----
|
|
|
-
```
**Explanation:**
- **Field Windings:** Winding with multiple taps.
- **Taps:** Points along the winding that provide different effective number of turns.
- **Effect:** By selecting different taps, the number of turns in the field winding changes. This alters the magnetic field strength and thus the speed of the motor.
**Operation:**
1. **Tap Selection:** By changing the tap point, you effectively change the field winding’s resistance and the number of turns in the winding.
2. **Field Flux Variation:** Changing taps will vary the field flux. A lower number of turns (tap closer to the end) will decrease the flux, increasing the speed, while a higher number of turns (tap closer to the beginning) will increase the flux, decreasing the speed.
### Summary
- **Field Diverter Method:** Uses a resistor in parallel with the field winding to bypass some current, reducing the field flux and increasing speed.
- **Tapped Field Method:** Uses multiple taps on the field winding to change the number of turns, thereby altering the field flux and controlling the speed.
Both methods offer ways to control the speed of a DC series motor by adjusting the field flux, but they achieve this in different ways.
### 1. Field Diverter Method
**Description:**
In a DC series motor, the field windings and the armature windings are connected in series. The speed of the motor is inversely proportional to the field flux (since the field flux is constant for a given current), and the field flux can be controlled by altering the current through the field winding.
**Method:**
In the Field Diverter Method, a diverter (or shunt resistor) is connected in parallel with the field winding. This diverter allows a portion of the current to bypass the field winding, thereby reducing the effective field current and hence the field flux.
**Diagram:**
```
+V
|
|
| +---------+ +---------+
| | | | |
| | Field | | Diverter|
| | Winding | | (Resistor)|
| | | | |
| +----||----+ +----||----+
| | |
| | |
| | |
| | |
| +------------+
| Armature
| Winding
| |
| |
| |
| ---
| -----
|
|
|
-
```
**Explanation:**
- **Field Winding:** Connected in series with the armature winding.
- **Diverter:** A resistor connected in parallel with the field winding.
- **Effect:** By adjusting the resistance of the diverter, you can control the amount of current bypassing the field winding. This reduces the overall field flux, which increases the speed of the motor.
**Operation:**
1. **Diverter Closed:** When the diverter resistance is very low, most of the current flows through the diverter, reducing the field current and hence the flux. This increases the speed.
2. **Diverter Open:** When the diverter is disconnected or has a high resistance, more current flows through the field winding, increasing the flux and thus reducing the speed.
### 2. Tapped Field Method
**Description:**
The Tapped Field Method involves providing multiple taps (connections) on the field winding. By selecting different taps, you change the effective number of turns in the field winding, thus varying the field flux.
**Method:**
In this method, the field winding is designed with several taps, and a switch or selector is used to connect the field winding to different taps. Each tap represents a different number of turns of the winding, altering the field flux.
**Diagram:**
```
+V
|
|
| +--------+--------+--------+--------+
| | Tap 1 | Tap 2 | Tap 3 | Tap 4 |
| | | | | |
| +----||----+----||----+----||----+----||
| | | | |
| | | | |
| | | | |
| | | | |
| Armature Winding
| |
| |
| |
| ---
| -----
|
|
|
-
```
**Explanation:**
- **Field Windings:** Winding with multiple taps.
- **Taps:** Points along the winding that provide different effective number of turns.
- **Effect:** By selecting different taps, the number of turns in the field winding changes. This alters the magnetic field strength and thus the speed of the motor.
**Operation:**
1. **Tap Selection:** By changing the tap point, you effectively change the field winding’s resistance and the number of turns in the winding.
2. **Field Flux Variation:** Changing taps will vary the field flux. A lower number of turns (tap closer to the end) will decrease the flux, increasing the speed, while a higher number of turns (tap closer to the beginning) will increase the flux, decreasing the speed.
### Summary
- **Field Diverter Method:** Uses a resistor in parallel with the field winding to bypass some current, reducing the field flux and increasing speed.
- **Tapped Field Method:** Uses multiple taps on the field winding to change the number of turns, thereby altering the field flux and controlling the speed.
Both methods offer ways to control the speed of a DC series motor by adjusting the field flux, but they achieve this in different ways.