BOMA Electrical Motor Controls with 100% correct answers.docx, Exams of Biology

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BOMA: Electrical

Motor Controls

with 100%

correct answers

A holding contact or maintaining contact in a magnetic motor starter is normally connected in parallel with the? - answer Stop push button, start push button, and starter coil The armatures of both AC and DC contactors must move freely or? - answer all the contacts may weld together Which of the following devices prevent motors from drawing too much current? - answer overloads

The primary difference between a motor starter and a motor contactor is the starter has an? - answer overload protection The purpose of a reduced motor is to? - answer reduce voltage on motor starter Two speed motors require 2 sets of overloads to monitor the motor heating characteristics at each speed? - answer true Over current protection is provided for an electric motor to prevent damage to the windings from the heating effect of excessive current? - answer true The current interrupting capability of a fuse breaker is to? - answer the maximum amperage it should conduct during normal operation Reduce voltage starting is used as a means of? - answer reducing the starting current

The speed of an AC squirrel cage motor can be changed by? - answer Changing the number of poles A short circuit ground fault device may consist of? - answer A fuse and a circuit breaker A small size motor starter is given the designation of 00? - answer True In a process control, the time it takes for a change in the process to be felt at the measuring device is called? - answer delay A relay is a device that can transfer an action from one circuit to another without an electrical connection between the two circuits? - answer True What is meant by EP switch? - answer Electric Pneumatic operated switch

When using a fuse jumper for troubleshooting, be sure never to connect the jumper between? - answer L1 and L The first thing to check when a system is down and won't run at all is? - answer The AC power supply Improper alignment of the pole faces can cause excessive hum in a AC electromagnetic or solenoid? - answer True To indicate a good diode an ohm meter should? - answer Low resistance in one direction and high resistance in the other direction Unbound resistance readings between the windings of a three-phase motor indicates the motor windings may? - answer Be breaking down A motor control circuit that allows the motor to automatically start after power is restored

provides low voltage release? - answer Is said to be wired across the line is provided What determines the speed of an induction motor? - answer Number of poles What is made when an electric current flow through the turns of a coil? - answer A magnetic field Rheostats are generally used in a motor controls for? - answer Specially designed motors How do you change the rotation of a three phase motor? - answer Change any 2 of the 3 wires The actual full load amps of a motor are found? - answer Nameplate of the motor The centrifugal switch of a single phase induction motor is connected in series with the ______ windings? - answer start windings

Synchrononomous motors have? - answer stator and magnetic force Return overload current in reference to motor circuits refers to? - answer Any load current that exceeds rated motor current A generator? - answer Changes mechanical power into electrical power A machine that converts mechanical power into electrical power is called a? - answer A generator and alternator Distilled water should be added to a battery when? - answer when level is below the plates The electrical energy that a battery can deliver is measured in? - answer amphours

When manually switching from normal to auxiliary power can be accomplished by? - answer using an automatic transfer switch What are the three main components of an uninterruptible power supply? - answer Rectifier, batteries, inverter Flex? - answer Provides a good grounding path when used as an equipment grounding conductor The size of a ridged metal conduit is determined by the? - answer ID When soldering conductors are used in electrical construction, the most suitable fluxs is? - answer paste To which of the following wires is the rounded prong of a three prong plug connected? - answer grounding wire

The transformer connections marked with an X are? - answer secondary In a transformer to which the input voltage is applied is the? - answer primary Fish tape can be made of? - answer Tempered steel, nylon, would steal cable A motor starter is a conductor with a _____ built in? - answer Overload It may motor pulls 5 amps of operating current, a good choice of fuse would be? - answer 7.5 amp slow blow A normally closed relay contact will be _____ when the relay is _____? - answer Closed, de- energized The most practical switch used when the neutral connection must not be broken is a _____ switch? - answer Single throw

A _____ is used to measure electrical potential? - answer voltmeter In anmeter is connected in series with the load? - answer True When a conductor passes through a magnetic field, a current flow/field is always produced?

• answer True A 4S box is the most frequently used in one of the situations shown below. Which is it? - answer Junction box What is the material typically used in the manufacturing of metallic boxes used in residential wiring? - answer Steel Metering of utility company services to a building is usually done at? - answer The service entrance point A _____ is used to measure resistance? - answer ohmmeter

A_____is used to measure current? - answer ampmeter The difference between jogging and inching circuits is that? - answer Jogging circuits remain energized for a specific amount of time, while inching circuits are energized only until the inch bunted his released. Most magnetic starters use double break contacts because the arc voltage is reduced to half (1/2) its total value at each break. - answer True The current rating of a contactor or starter is rated for? - answer Each individual contact in the contactor or starter Combination starters designed to have disconnect and the motor starter include in one single enclosure? - answer True

A starter that has 3 electrical separate sets of a power contacts would be classified as a 3 pole motor starter? - answer True A short circuit ground fault device may consist of? - answer Fuse and circuit breaker In a process control, the time it takes for a change in the process to be felt at the measuring device is called? - answer Delay A set of normally open contacts are_____when the relay is_____? - answer Open, de- energized A combination motor starter always includes?

• answer Circuit breaker, fuse and disconnecting device The most difficult arcs to extinguish on a set of contacts are? - answer DC arcs The symbol of normally closed contacts are two parallel vertical lines? - answer False

To indicate a good diode and ohmmeter should show? - answer Low resistance in working direction and high resistance in the other direction Replacing overload heaters or fuses on a three-phase circuit you should? - answer Replace all three Interrupting the circuit of one of the supply lines to a three-phase motor would? - answer Make the motor single phase The major cause of most motor failures is? - answer deterioration of the insulation To indicate a good capacitor, the needle on an ohmmeter should? - answer Swing to 0 and slowly move to ¼, 1/3, ½ to way across the scale to infinity Which of the following devices does not use a motor speed control? - answer Clocks

Rotary motion is produced by a motor. The twisting force causing the motion is called? - answer Torque Which of the following would not be the cause of excessive motor vibration or noise? - answer Defective starter The overload protection devices protects? - answer The motor windings A device used to measure the rotating speed of the motor is called? - answer tachometer Synonomous motors have a? - answer rotors and stators Generators make electricity by? - answer rotating armature in a magnetic field Storage batteries are rated for ampere hour capacity and? - answer voltage

What is a stranded conductor? - answer conductor composed of a group of wires Thinwall conduit is another name for? - answer EMT A sudden current surge that occurs when a motor driven appliance is turned off? - answer normal overcurrent In a transformer the coil to which the induced voltage is applied is the? - answer primary The connections on a transformer marked H are the? - answer primary The input voltage of a transformer is applied to a winding called the? - answer primary A 3 way switch is essentially a? - answer single pole double throw switch

If a switch can be closed by moving a contact to only one position, it is a _____ switch? - answer single throw Which of the following is the color code of the insulation on the neutral wire? - answer white When soldering conductors are used in electrical construction, the most suitable flux is? - answer rosin What is the purpose of grounding? - answer to insure safety What is the abbreviation for heat resistant thermoplastic insulation? - answer THHN Which type of overload device uses a bimetallic strip? - answer thermal The result of connecting to large current load? - answer overload