Starting a DC motor without a starter can lead to several issues, and the use of a starter becomes essential to address these challenges. A starter in the context of a DC motor refers to a device or a set of devices designed to control the motor’s starting process. Let’s delve into the reasons why a starter is needed for starting a DC motor:
1. Initial High Current Draw:
- Stall Condition: When a DC motor is initially switched on, it is at rest, and there is no back electromotive force (EMF) generated. As a result, the motor experiences a stall condition, drawing a high current from the power supply.
- High Starting Torque: The high current creates a high starting torque, which can cause mechanical stress on the motor components, including the armature and brushes.
2. Armature and Brush Wear:
- Excessive Wear: The high starting current can lead to excessive wear on the motor’s brushes and armature. This wear not only shortens the life of these components but can also result in arcing and sparking, further degrading their condition.
3. Voltage Drop:
- Voltage Drop in Power Supply: The initial high current draw during motor starting can cause a voltage drop in the power supply system. This can affect other devices connected to the same power supply, leading to potential operational issues in the broader electrical system.
4. Mechanical Shock:
- Mechanical Stress: The sudden application of high torque during the starting process can subject the mechanical components of the motor, such as the gearbox and connected machinery, to mechanical shock. This can lead to premature wear and reduce the overall lifespan of the system.
5. Back EMF:
- Delayed Generation: As the motor accelerates, back electromotive force (EMF) is generated, opposing the applied voltage. However, during the initial moments of starting, this back EMF is insufficient to counteract the high current draw.
- Current Limitation: A starter provides a controlled means to limit the initial current and gradually increase it as the motor accelerates. This helps prevent excessive current draw and associated issues.
6. Control of Starting Parameters:
- Speed and Torque Control: A starter allows for controlled acceleration of the DC motor, enabling the adjustment of starting parameters such as speed and torque. This control is particularly important in applications where precise control of the motor’s starting characteristics is required.
7. Reduced Electromagnetic Interference (EMI):
- Suppressing EMI: The controlled starting provided by a starter helps in suppressing electromagnetic interference (EMI) generated during the initial high-current phase. This is important in applications where EMI can interfere with other electronic devices.
8. Overcurrent Protection:
- Overcurrent Protection Features: Many starters come equipped with overcurrent protection features to prevent damage to the motor and associated components in the event of a fault.
In summary, a starter is essential for starting a DC motor to address the challenges associated with high initial current draw, mechanical stress, wear on components, voltage drop, and the need for controlled acceleration. It provides a systematic and controlled approach to motor starting, ensuring the longevity and reliability of the DC motor and the broader electrical system.
