Heating_Time_Constant_Motor_Presentation.pptx

semester 7th topic

1. GOVERNMENT ENGINEERING COLLEGE BILASPUR Session 2024-25 ELECTRIC DRIVE LAB Submitted to: Proff . – Uma Rathore Presented By Name :- Md Shamee Ansari Roll No.- 300702421056

2. Heating Time Constant of Short-Time Duty Motor

3. Introduction Objective: To study the heating time constant of a short-time duty motor. • Relevance : Used in applications like cranes, elevators, etc., where motors operate intermittently.

4. Apparatus Required and Setup Diagram Apparatus Required: • DC Motor Speed Control Trainer . • Heating Cooling Time Constant Unit . • Temperature Measuring Instrume nts (Thermocouple)

5. Theoretical Background Short-Time Duty Motor: The operation time of the motor is much shorter than the time it takes to heat up (the heating time constant). The motor is allowed to cool down to ambient temperature before it is operated again. Motor Losses: During motor operation, losses occur, mainly due to heat generated from copper losses (winding losses) and core losses (hysteresis and eddy currents).

6. Temperature Rise Formula: The temperature rise of the motor follows the equation: Where: θ m​: Actual temperature rise of the motor. θ ′m​: Permissible final temperature rise N: Duration of the motor operation (in seconds). T: Heating time constant of the motor.

7. Losses and Power Ratings Motor Losses: W c ​ : Core losses. W cu ​ : Copper losses (due to winding resistance). W LT ​: Total losses for continuous operation. W LX ​: Total losses for short-time duty operation. Losses Formula:

8. Where: 𝛼 : Ratio of core losses to copper losses at full load . 𝑃 𝑥 ​ : Short-time duty rating power. 𝑃 𝑇 ​ : Continuous rating power.

9. Start with the Temperature Rise Formula: Substitute Losses into the Formula: By analyzing the losses during short-time duty, we get: Derive the Heating Time Constant Formula: The heating time constant TTT can now be derived using the above equations: Heating Time Constant Derivation

10. Results and Graph • Calculated Heating Time Constant: Derived from the above formula . • Graph shows temperature rise approaching max permissible value over time.

11. Conclusion and Precautions Conclusion: • The heating time constant of the motor was successfully studied. • Motor's temperature rise should be controlled to avoid overheating. Precautions: Ensure connections are tight and secure. Carefully monitor the temperature rise using calibrated instruments.

12. Thank you