Cranes Load Characteristics
Cranes and hoists are used for lifting and moving heavy objects. Their operation typically involves:
- Starting under load (lifting a heavy object from rest).
- Frequent starting and stopping.
- Changing direction (lifting up and lowering down).
Load Type Explanation
Based on their operation, the load offered by cranes and hoists is best described as:
- Reversing: Because they can lift (move upwards) and lower (move downwards), their direction of operation reverses.
- Heavy start: They often need to start lifting when the load is substantial, requiring high initial torque.
Therefore, the load type is a reversing, heavy start load.
Why Other Options Are Incorrect
- Gradually varying load: This implies a slow, steady change, not the sudden application of torque needed to lift heavy items.
- Non-reversing, no-load start: Cranes frequently reverse direction and almost always start while carrying a load.
- Reversing, light start: While cranes do reverse, they frequently start under heavy loads, not just light ones.
Important Questions from Electric Drives
In a single-phase DC drive the power modulator will be ______.
In motor operations, if at any time ______, the motor will accelerate.
Which of the following statements about the nature of speed control required by different industrial drives is INCORRECT?
______ are used in control systems to attain the mechanical matching of the motor to the load.
The difference between the tooth space and tooth width in mechanical systems which is essential for rapid working gear transmission is known as ______.
