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When motors were first introduced, they were started and stopped by _____?
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One of the advantages of using a double-break contact instead of a single-break contact is that a double-break contact ____?
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ELEC 151 Final
| Question | Answer |
|---|---|
| When motors were first introduced, they were started and stopped by _____? | Knife switches |
| One of the advantages of using a double-break contact instead of a single-break contact is that a double-break contact ____? | Has a higher contact rating in a smaller space. |
| Copper contacts have been replaced with ____ alloy contacts because of the problems of using copper with knife switches. | Low-resistance silver |
| A ____ diagram shows the connection and placement of an installation or its component devices or parts. | Wiring |
| ____ interlocked contactors are two contactors that are connected in such a way that both sets of contacts cannot be closed at the same time. | Mechanically |
| Manual starters are selected based on phasing, number of poles, voltage, starter size, and _____? | Enclosure type |
| A ____ is a condition that occurs when a motor is loaded so heavily that the motor shaft cannot turn. | Locked rotor |
| The three stages that a motor must go through in normal operation are resting, starting, and _____? | Operating |
| Fuses or _____ are used to protect a motor against very high currents, short circuits, or a ground fault. | Circuit breakers |
| A 120 V, 1Φ power source has one hot wire and ____ neutral wire(s). | One |
| A 230 V, 1Φ power source has two hot wires and ____ neutral wire(s). | Two |
| A 3Φ power source has ____ hot wires and zero neutral wires. | Three |
| A ____ is a device that is used only periodically to remove electrical circuits from their supply source. | Contactor |
| Manual contactors are normally used with ____ circuits and resistance loads. | Control |
| The main device in an overload relay is the ____? | Eutectic Alloy tube |
| A manual starter is a ____ with an added overload protection device. | Contactor |
| Overload protection devices are required by the ____? | NEC |
| ____ temperature is the temperature of the air surrounding a motor. | Ambient |
| A ____ alloy is a metal that has a fixed temperature at which it changes directly from a solid to a liquid state. | Melting |
| A starter may be reset after an ____ is removed. | Overload |
| Enclosures provide ____ and electrical protection for the operator and the starter. | Mechanical |
| A ____ is a control device that uses pushbuttons to energize or de-energize the load connected to it. | Contactor |
| ____ contacts are contacts that break the electrical circuit in two places. | Magnetic |
| NEMA Type ____ enclosures are intended for indoor use primarily to provide a degree of protection against human contact with the enclosed equipment in locations where unusual service conditions do not exist. | 1 |
| Manual motor starters are used in application such as air compressors, conveyor systems, and _____? | Drill presses |
| A ____ overload measures the strength of the magnetic field around the wire instead of converting the current into heat. | Magnetic |
| ____ power line(s) must be broken when using a contactor to control a 3Φ load. | Three |
| ____ arcs are the most difficult to extinguish on a set of contacts. | DC |
| ____ are used to help confine, divide, and extinguish arcs for each set of contacts. | Arc chutes |
| The power rating of a contactor or motor starter ____ as the NEMA number (size 1, 2, etc.) of the contactor or motor starter increases. | Increases |
| The current rating of a contactor or motor starter is the rating for _____? | Each individual contact |
| The main difference between a contactor and a motor starter is the addition of ____ to the motor starter. | Overloads |
| Two overload relays used to protect motors are thermal and ____ overload relays. | Magnetic |
| Ambient temperatures, full-load current rating, and _____ must be known when selecting the overloads for a motor starter. | Service Factor |
| An inherent motor protector is designed to protect a motor from ____? | Overload |
| ____ contactor assemblies may have several sets of contacts. | AC |
| A ____ relay is an overload relay which resets automatically. | Bimetallic OL |
| A ____ is built into an overload device to indicate to the operator that an overload has taken place within the device. | Trip Indicator |
| ____ are used on large motor starters to reduce the current flowing to the overload relay. | Overload current transformer |
| An ____ is a device that dissipates the energy present across opening contacts. | Arc suppressor |
| As ambient temperature increases, _____ current is needed to trip overload devices. | Less |
| An ____ performs the same function as a motor starter, but can also vary motor speed, reverse the motor, and display operating information. | Electronic OL |
| A ___ is an electronic device that changes AC into DC. | Transformer |
| An ____ is an electronic device that changes DC into AC. | Inverter |
| Article ____ of the NEC covers the design and installation of electronic systems that contain motors, motor circuits and motor controllers. | 430 |
| A ____ is then number of completely isolated circuits a relay can switch at one time. | Pole |
| A ____ is the number of closed contacts per pole. | Throw |
| A ____ is the number of separate places on a contact that open or close an electrical circuit. | Break |
| An ____ relay is used to ramp up the voltage applied to a load. | Analog switching |
| A ____ relay is an SSR that turns ON a load when the voltage at the load crosses near or at the zero point. | Zero switching |
| A ____ relay is normally a plug-in relay and does not have convertible or replaceable contacts. | Reed |
| A _____ relay normally includes replaceable, convertible, or interchangeable contacts. | General-purpose |
| A ____ relay is activated by the presence of a magnetic field. | Reed |
| An ____ relay is an SSR that allows the load to be turned ON at any point on the AC sine wave. | Instant ON switching |
| A ____ relay's contacts are sealed and impervious to dust, humidity, and fumes, and have a long service life. | Reed |
| Relay manufacturers use a common ____ to simplify the identification of relays. | Code |
| Typical contact life ratings for electromechanical relays are between ____ and ____ operations | 100k and 500k |
| Typical mechanical life ratings for electromechanical relays are between ____ and ____ operations. | 1 million to 10 million |
| A ____ is a circuit that protects contacts by providing a nondestructive path for generated voltage as switch is opened. | Contact protector circuit |
| A ____ is a resistor whose resistance is inversely proportional to the voltage applied to it. | Varistor |
| ____ is the ability of a device to impede the flow of heat. | Thermal resistance |
| An advantage of an EMR is ____? | Very low contact voltage drop, requiring no heat sink. |
| A limitation of EMRs is ____? | They generate EMI on power lines |
| ____ is the trip point from the time the motor starts until the first time it overloads. | Cold Trip |
| ____ is the trip point after the overloads have tripped and have been reset. | Hot trip |
| When a starter is set for ____, the motor gradually accelerates over a programmable time period. | Soft start |
| Motor stopping modes include soft stop, pump control, and ____? | Brake stop |
| ____ are temporary, unwanted voltages in an electrical circuit. | Transient voltages |
| The ____ is a method of SSR replacement in which a logical sequence is used to determine the reason for failure. | Circuit analysis method. |
| ____ is a phenomenon that occurs when a relay fails to turn OFF because the current and voltage in the circuit reach zero at different times. | Half-waving |
| A ____ is a solid-state control device that controls an industrial process or machine. | Programmable Logic Controller (PLC) |
| A ____ is a timer that maintains its current accumulated time value when its control input is interrupted or removed. | Retentive Timer |
| A _____ is a timer that does not maintain its current accumulated time value when its control input is interrupted or removed. | Non-retentive timer |
| A _____ is a device in which the contacts change position immediately and remain changed for the set period of time after the timer has received power. | One-shot timer |
| A ____ is a timer that operates with equal ON and OFF time periods. | Symmetrical recycle timer |
| A ____ is a timer that is controlled by an external transistor from a separately powered electronic circuit. | Transistor controlled timer |
| A ____ is a timer controlled by an external sensor in which the timer supplies the power required to operate the sensor. | Sensor controlled timer |
| An ____ is a device used to count inputs and provide an output (contacts) after the preset count value is reached. | UP counter |
| A ____ is a counting device that keeps track of the total number of inputs and then displays the counted value. | Totalizer |
| An ____ is a device used to count inputs from two different inputs. | UP/DOWN counter |
| ____ diagrams are the actual diagrams which match the logic of manufactured product line diagrams. | Wiring |
| ____ timers are used in applications that require a load to remain energized even after the input control has been removed. | Off-delay |
| Four major categories of timers are ______? | Dashpot, synchronous clock, solid-state, programmable |
| A ____ circuit provides a very accurate timing function at the most economical cost. | Solid-state timing |
| A ____ is a continuous power transmission belt with a trapezoidal cross section. | V-belt |
| A _____ is filled out for each breakdown or equipment problem immediately after the problem is solved. | Troubleshooting report |
| A ____ load is a load in which the applied force is perpendicular to the axis of the rotation. | Radial |
| Thermal expansion is a dimensional change in a substance due to a change in _____? | Temperature |
| ____ misalignment is a condition where two shafts are parallel but the pulleys are not on the same axis. | Offset |
| Improper lubrication includes _____? | lubricant contamination, over- and under-lubrication. |
| _____ is generally caused by improper machine foundations, pipe strain, soft foot, or thermal expansion. | Misalignment |
| ____ is the magnification of vibration and its noise by 20% or more. | Resonance |
| Preventive maintenance _____? | Increases efficiency, reduces cost, and minimizes health and safety problems |
| ____ is the condition where the centerlines of two machine shafts are placed within specified tolerances. | Alignment |
| _____ is service on failed equipment that has not received scheduled maintenance such as cleaning or lubrication. | Breakdown maintenance |
| ____ is work on long term projects that require advanced planning and more time than typical maintenance tasks. | Project work |
| An _____ is taken when the motor is placed in service and every six months thereafter. | Insulation Spot Test |
| Work ____ is the order in which work is done based on its importance. | Priority |
| ____ is an analysis that uses high vibration frequencies to create an image or reading. | Ultrasonic Analysis |
| A dielectric absorption test is performed over a ____-min period. | 10 |
| _____ alignment is an alignment method that is used to align machinery. | Electronic reverse dial, Laser, and straightedge |
| A _____ is an antifriction roller-type bearing with long rollers of small diameter. | Needle bearing |
| The primary difference between facilities maintenance and industrial maintenance is ____? | Downtime cost |
| ____ may be offset or angular. | Misalignment |
| Standard _____ are designated as A, B, C, D, or E. | V-belts |
| _____ is maintenance performed to keep machines running with little or no downtime. | PM |
| As a rule of thumb, misalignment of a coupling by 0.0004" can shorten its life by _____? | 50% |
| ____ monitoring is the monitoring of equipment at all times. | Continuous |
| A _____ is a rigid steel support for firmly anchoring and aligning two or more rotating devices. | Base plate |
| ____ and _____ are used to adjust the height of a machine. | Shims, spacers |
| The accuracy of ____ alignment is approximately 1/64". | Straightedge |
| Belts commonly used in the industry include _____. | Flat belts, V-belts, timing belts |
| _____ is work that is planned and scheduled for completion. | Scheduled maintenance. |
| A _____ is a device that joins two precisely aligned shafts within a common frame. | Rigid? |
| All plumbing must be properly aligned and have its own _____ even when unattached. | Permanent support |
| A ____ bearing is an antifriction bearing that permits free motion between a moving part and a fixed part by means of balls confined between inner and outer rings. | Ball |
| The industry standard is to interchange leads L1 and _____ to reverse the direction of rotation of a 3Φ motor. | L3 |
| A ______ is the arrangement of contacts in such a way that both sets cannot be closed at the same time. | Mechanical interlock |
| It is necessary to interchange only the _____ winding to reverse the direction or rotation of a 1Φ motor. | Leads of the running |
| The _____ winding of a 1Φ motor normally has a much lower resistance than the ____ winding. | running, starting |
| A manual starter can be used to reverse the direction of current flow through the ____ of all DC motors. | Armature |
| A _____ is a manual switch made up of moving contacts mounted on an insulated rotating shaft. | Drum switch |
| _____ wiring is wiring in which each component in a circuit is connected to the next component. | Point-to-point |
| When troubleshooting a reversing circuit, the voltage must be within _____% of the control circuit rating. | 10 |
| A _____ circuit allows the operator to start the motor for a short time without memory. | Jogging |
| A drum switch is not considered a motor starter because the switch does not contain _____? | Protective overloads |
| Although most magnetic reversing starters provide mechanical interlock protection, some circuits are provided with a secondary backup system that uses _____ contacts to provide electrical interlocking. | Auxiliary |
| In a _____ reversing circuit, interlocking is accomplished by programming, not hard wiring, normally closed auxiliary contacts into the circuit. | PLC |
| The stop, forward, and reverse pushbuttons are wire to the ____ section of a PLC. | Input |
| The forward and reverse starting coils are wired to the ____ section of a PLC. | Output |
| ____ switches can be incorporated to shut an operation down if a load travels far enough to be unsafe. | Limit |
| When wiring using a ______, each wire in the control circuit is assigned a reference point on the line diagram to identify the different wires that connect components in the circuit. | Terminal strip |
| _____ eliminate the need for forward and reversing starters because they can be used to select motor direction. | Motor drives |
| A _____ can monitor and control all motor control functions, but cannot directly monitor and display motor parameters such as voltage, current, frequency, and power. | PLC |
| A drum switch may be purchased with maintained contacts or _____ contacts. | Spring return |
| _____ interlocking may be used in either or both mechanical or auxiliary interlocking. | Pushbutton |
| Although the power circuit and control circuit operate together to control a motor, they are electrically isolated from each other through a ______? | Transformer |
Created by:
thrak76