Question 22 CEL01 - Chief Engineer - Limited

The Correct Answer is D **Explanation for Option D (Correct Answer):** Automatic electric brakes used in industrial applications, such as those found on capstans (winches or warping heads) or hoists, are typically designed as "failsafe" mechanisms. 1. **Spring Set:** The normal, de-energized state of the brake is "set" or engaged. This engagement is achieved by mechanical force, usually provided by heavy compression springs. When no electricity is supplied to the brake mechanism, the springs push the brake pads or disc into contact, stopping rotation. 2. **Electrically Released:** To operate the capstan, an electromagnet (solenoid) within the brake assembly is energized with electricity. This magnetic force overcomes the force of the springs, pulling the brake pads/disc apart and allowing the motor shaft to rotate freely. 3. **Automatic Setting upon Power Removal:** Since the spring force provides the braking action (set) and the electric power provides the release, when the electric power is removed from the drive motor (and thus the brake solenoid), the electromagnet loses its holding force. The springs immediately re-engage the brake, automatically stopping the capstan. Therefore, the statement "The brake is spring set and electrically released, and the brake automatically sets when electric power is removed from the electric drive motor" is accurate for a failsafe electric capstan brake. **Explanation of Why Other Options Are Incorrect:** * **A) The brake is electrically set and spring released, and the brake automatically releases when power is removed from the electric drive motor.** * This describes an energy-consuming brake mechanism that is not failsafe. A standard capstan brake is **spring set** (failsafe), not electrically set. Furthermore, removing power causes the brake to **set** (stop the motion), not release. * **B) The brake is spring set and electrically released, and the brake automatically releases when electric power is removed from the electric drive motor.** * While the first half ("The brake is spring set and electrically released") is correct, the second half is contradictory. If the brake is spring set, removing the electrical power required for the release mechanism will cause the brake to **set** (engage), not release. * **C) The brake is electrically set and spring released, and the brake automatically sets when electric power is removed from the electric drive motor.** * This is incorrect because the brake is **spring set** (not electrically set). If the brake were electrically set, removing power would cause it to spring release, which is the opposite of the required failsafe function (stopping the motion when power is lost).