21. Which is not a correct attribute of the optocoupled relay circuit shown (a) it is possible to have different voltage levels in the input and output circuits (b) voltage spikes or electrical noise is eliminated (c) the LED acts as a photo sensor (d) the LED section of the optoisolated relay acts like the coil of the electromechanical relay Control signal Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education Input LED a Photodetector EL Power transistor Photo courtesy Futuriec, www.futuriec.com Load Direct current 22. The soft starter is a reduced voltage starter that restricts starting current by applying the line voltage (a) directly (b) through a resistor (c) intermittently (d) in a ramp 23. The full-load current rating shown on the motor's nameplate is used to determine the ampacity of the conductors (a) True (b) False 24. A motor overload condition is normally caused by (a) excessive motor load (b) a short-circuit (c) a ground-fault (d) an open equipment grounding conductor 25. Complete this statement: In general, each motor requires a disconnecting means that is located within sight of the motor. In sight from is defined as being visible and not more than feet in distance from one another after is has come to a stop (a) braking (b) starting 26. A zero speed or plugging switch prevents the motor from (c) reversing (d) hopping 27. Dynamic braking is achieved by reconnecting a rotating motor to act as a (a) converter (b) dynamo (c) generator (d) magnetic starter immediately after it is turned off 28. When voltage is applied across a diode in such a way that the diode allows current to flow, the diode is said to be (a) short circuited (b) open circuited (c) forward-biased (d) reverse-biased 29. Latching relays can provide circuit continuity during power failures (a) True (b) False
Protection System
A system that protects electrical systems from faults by isolating the problematic part from the remainder of the system, preventing power from being cut from healthy elements, improving system dependability and efficiency is the protection system. Protection devices are the equipment that are utilized to implement the protection system.
Predictive Maintenance System
Predictive maintenance technologies are designed to assist in determining the state of in-service equipment so that maintenance can be scheduled. Predictive maintenance is the application of information; proactive maintenance approaches examine the condition of equipment and anticipate when it should maintain. The purpose of predictive maintenance is to forecast when equipment will fail (depending on a variety of parameters), then prevent the failure through routine and corrective maintenance.Condition monitoring is the continual monitoring of machines during process conditions to maintain optimal machine use, which is necessary for predictive maintenance. There are three types of condition monitoring: online, periodic, and remote. Finally, remote condition monitoring allows the equipment observed from a small place and data supplied for analysis.
Preventive Maintenance System
To maintain the equipment and materials on a regular basis in order to maintain those running conditions and reduce unnecessary shutdowns due to unexpected equipment failure is called Preventive Maintenance (PM).
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