Question

State suitable single phase motor for following applications: (i) Table fan (ii) Mixers and Grinders

Answer 1

When selecting suitable single-phase motors for specific applications like table fans and mixers/grinders, it’s important to consider the operational requirements of each device, including torque, speed, and efficiency. Here’s a detailed look at suitable motor types for both applications:

### (i) Table Fan

**Suitable Motor: Capacitor Start Induction Motor (CSIM)**

**Characteristics:**
- **Type:** Split-phase or Capacitor Start Induction Motor (CSIM)
- **Speed:** Typically operates at 1500 RPM (for 50 Hz supply) or 1800 RPM (for 60 Hz supply).
- **Starting Torque:** Provides good starting torque, which is essential for overcoming the inertia of the fan blades.
- **Efficiency:** These motors are relatively efficient and suitable for continuous operation.
- **Noise Level:** They generally run quietly, which is important for consumer comfort.
- **Power Rating:** Commonly ranges from 50 to 100 watts for standard table fans, but can go higher for industrial applications.

**Operation:**
- The motor uses a capacitor to create a phase shift, resulting in a stronger starting torque compared to a standard split-phase motor. This feature helps the fan start smoothly and maintain a consistent speed during operation.

### (ii) Mixers and Grinders

**Suitable Motor: Universal Motor**

**Characteristics:**
- **Type:** Universal Motor (AC/DC Motor)
- **Speed:** Can operate at a high speed, typically ranging from 10,000 to 20,000 RPM.
- **Starting Torque:** Very high starting torque, ideal for applications that require quick acceleration and handling varying loads.
- **Efficiency:** While not as efficient as induction motors, universal motors are effective for short bursts of high power.
- **Power Rating:** Usually ranges from 300 to 1000 watts, depending on the capacity of the mixer or grinder.

**Operation:**
- Universal motors can run on both AC and DC power, making them versatile for different applications. The high speed and torque allow for efficient mixing and grinding of various ingredients. However, they can be noisier and generate more heat, so good ventilation is essential during operation.

### Summary

- **Table Fan:** A Capacitor Start Induction Motor is suitable due to its efficiency, quiet operation, and sufficient starting torque.
- **Mixers and Grinders:** A Universal Motor is ideal because of its high speed and torque, enabling effective performance for varying loads in a short period.

### Conclusion

In conclusion, the choice of motor significantly impacts the performance and efficiency of the device. For table fans, a CSIM provides a balanced performance for continuous use, while a universal motor is best suited for mixers and grinders where high starting torque and speed are critical for effective operation. Understanding these characteristics helps in selecting the right motor for the application, ensuring optimal performance and reliability.

Answer 2

Choosing the right single-phase motor for various applications depends on several factors, including the mechanical requirements, efficiency, and operating conditions. Here’s a detailed explanation of suitable single-phase motors for the given applications:

### (I) Table Fan

**Motor Type: Capacitor-Start, Capacitor-Run Motor**

**Characteristics:**
- **Starting Mechanism:** The table fan typically uses a capacitor-start, capacitor-run motor. This type of motor has a capacitor both for starting the motor and for running, which helps improve efficiency and performance.
- **Speed:** Usually, table fans operate at a constant speed. Therefore, a motor with a fixed speed, often around 1350 RPM (revolutions per minute), is appropriate.
- **Efficiency:** These motors are designed for continuous operation and are relatively efficient for the power they consume.
- **Power Rating:** Table fans generally require motors with a power rating between 40 watts to 70 watts, though some larger models might use motors up to 100 watts.
- **Design Considerations:** The motor should be designed for quiet operation and low vibration since table fans are often used in residential settings where noise can be a concern.

**Example Motor:** A typical single-phase capacitor-start, capacitor-run motor with a power rating of around 60 watts and an RPM of 1350.

### (II) Mixers and Grinders

**Motor Type: Universal Motor**

**Characteristics:**
- **Starting Mechanism:** Mixers and grinders commonly use universal motors, which can run on both AC and DC supply. These motors are known for their high speed and torque, which are essential for applications involving chopping, grinding, or mixing.
- **Speed:** Universal motors can operate at high speeds, often in the range of 10,000 to 20,000 RPM. The high speed is necessary for efficient operation of mixers and grinders.
- **Power Rating:** Mixers and grinders typically require motors with power ratings between 500 watts to 1000 watts or more, depending on the capacity and intended use of the appliance.
- **Efficiency:** While universal motors are less efficient compared to induction motors, their ability to provide high speed and torque makes them suitable for this application.
- **Design Considerations:** The motor needs to be robust and able to handle frequent starts and stops. It should also be designed for continuous operation under varying loads.

**Example Motor:** A single-phase universal motor with a power rating of 750 watts and a high-speed capability (around 15,000 RPM).

### Summary

- **Table Fan:** Capacitor-start, capacitor-run motor (40-100 watts, 1350 RPM).
- **Mixers and Grinders:** Universal motor (500-1000 watts, 10,000-20,000 RPM).

Selecting the appropriate motor for each application ensures that the device operates efficiently and reliably, meeting the specific needs of its intended use.