Quiz
Power Sources
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Perguntas do quiz (32)
1In GTAW welding, a strong +ve voltage is applied to the Tungsten electrode because of its high melting point
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2To initiate an arc requires high current and low voltage power
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3How much current will flow through a resistance of 200 ohms when 100 volts is applied
- A0.5 amps
- B5.0 amps
- C2.0 amps
- D20 amps
4A generator consists of rotating conductors in a stationary magnetic field and an alternator consists of rotating magnetic field inside the conductor windings
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5In a series circuit, current may be accurately measured at any point because there is only a single path for current flow
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6The length of welding cables has little of no effect on the performance of the equipment
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7Welding cable sizes are according to the American Wire Gauge; #6 is bigger than #4
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8Voltage measurement must be made as close to the arc as possible to avoid voltage drop through the power circuit.
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9What is the purpose of an inverter?
- AConverts DC Current to AC Current of same frequency
- BConverts DC Current to High Frequency AC Current
- CConverts AC Current to DC Current
10When evaluating alternating current circuits, RMS values are used rather than peak values. Why?
- AThe peaks are opposite to each other and therefore cancel out
- BRMS values allow AC circuits to be evaluated in an equivalent manner to DC circuits
- CAverage current is used, not RMS, when assessing AC circuit in a similar manner to DC circuits
11Transformers designed for higher frequencies require much less iron core and windings than those designed for low frequencies
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12The advantage of inverter based power source is that the circuitry is more simplified that the conventional power source
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13Which metal has the lowest resistivity?
- AAluminum
- BTungsten
- CCopper
- DIron
14Welding cable length should be kept minimum where possible. Because there is a voltage drop over length of cable, it must be compensated in order to maintain the correct welding voltage.
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15In parallel electrical circuits, the voltage across two parallel paths is the same since each path is connected to the same voltage source. Select the correct statement.
- AIn each parallel path the resistance must be equalised
- BThe current flowing in each parallel path must be the same as the voltage
- CThe current flowing in each parallel path depends on the value of resistance in each path
16What are the basic classifications of welding power sources?
- ACV Power Source
- BCC Power Source
- CCV and CC Power Source
17How much current will flow through a resistance of 50 ohms when 25 volts is applied?
- A2.0 amps
- B0.5 amps
- C5.0 amps
- D0.2 amps
18Inductance is a property of a circuit just as resistance is a property. Changing current flow through a circuit creates an "induced" magnetic field. What effect does the frequency of AC current have on the strength of the induced magnetic field?
- ANone
- BThe higher the frequency, the weaker the induced magnetic field
- CThe higher the frequency, the stronger the induced magnetic field
19If more than one welder is working on a structure, DC machines must be connected to the same polarity.
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20Amongst problems caused by the incorrect operation of ancillary equipment: too low a wire feed roller pressure may result in wire slippage, leading to bum-back or a weld nozzle clogged with spatter which can result in a heavily oxidized weld.
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21Steep slope minimises the change in current due to changes in arc length (constant current). In some situations a flatter slope is used to provide some change in current when arc length changes - a common preference when welding pipe joints.
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22What type of output current is usually required for GTAW?
- AVery high open circuit voltage
- BHigh frequency open circuit current
- CConstant current
- DLow power factor
- EHigh duty cycle current
- FConstant voltage
23Constant current power supplies can be used, both in DC and AC
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24Constant voltage power supply is required for GMAW process
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25Motor generators are bulky and heavy, have many moving parts which are prone to wear and require frequent maintenance.
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26A transformer is a device which converts utility AC to DC welding current
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27A disadvantage of SCR control is that the output is very "choppy." The output is smoothed out by the addition of a bank of capacitors.
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28One of the simplest ways of controlling the output of a welding transformer is to change the efficiency of coupling. How can this be done?
- ASlide a piece of wood between the primary and secondary coils
- BDesign the transformer with either a moving core or moving primary coils
- CDesign the transformer with a number of taps to select different output curves
- DUse the timed firing of SCR's to control total conduction time
29A conventional diode placed in a circuit allows the passage of current in one direction only. A silicon controlled rectifier (SCR) operates slightly differently. How does it work?
- Aan SCR conducts current in both directions until turned on and current flow is then prevented
- Ban SCR is non-conductive until turned on and then allows current to flow in both directions
- Can SCR is non-conductive until turned on and then allows current to flow in one direction only until the flow of current stops
- Dan SCR is a unique device which allows only AC current to flow
30Inverter based power supplies for GTAW are now offering the ability to increase AC welding current frequency. Increasing the frequency can improve arc focusing when using alloyed tungstens for aluminum welding.
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31What is the high frequency unit used for in GTAW or PAW power sources?
- ATo preheat the joint
- BTo reduce the overall power efficiency
- CTo promote deeper penetration
- DTo provide arc starting and arc stability
32In high frequency systems, incoming AC line voltage is stepped up to several thousand volts by a transformer. Select the correct statement.
- AHigh frequency systems are limited to less than 4000 volts for safety reasons
- BThe spark gap needs to be at least 75mm (3") wide for the spark to jump far enough to create the crackling arc
- CHigh frequency systems output high voltage but only low current
- DHigh frequency systems work with DC arcs
Informações
- Descrição
- CWB Level 2 (Flash Cards / Quizes) Quiz sobre Power Sources, criado por Grant Aden em 05-08-2015.
- Autor
- Grant Aden
- Idioma
- English
- Visualizações
- 4
- Etiquetas
- Avaliação
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