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NCCER Solar PV practice questions

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Question 1Solar PV Fundamentals and Safety

Under NFPA 70E, before any work on energized PV conductors, what is the first step in establishing an electrically safe work condition?

  1. Identify all sources of supply and disconnect them Correct answer.
  2. Install temporary grounding jumpers on the array
  3. Test the conductors with a non-contact voltage tester
  4. Notify the utility that work is beginning

Explanation

The electrically safe work condition process begins with identifying all sources of supply and then disconnecting them. Only after disconnecting and isolating can lockout/tagout, verification of de-energization, and grounding be applied in sequence.

Question 2Solar PV Fundamentals and Safety

A PV module's DC output remains energized whenever the module is illuminated. What is the primary safety implication of this for firefighters and service personnel?

  1. The array output drops to zero once the inverter is shut down
  2. The module terminals stay live and cannot be de-energized by a switch Correct answer.
  3. Covering the array with opaque tarps is never permitted
  4. Opening the DC disconnect removes all voltage at the module leads

Explanation

A PV module is a current-limited source that generates voltage whenever light strikes the cells, so no switch or disconnect can de-energize the module terminals themselves. Only blocking illumination or physically separating conductors removes that hazard.

Question 3Solar PV Fundamentals and Safety

What does the term 'irradiance' describe in PV system design and testing?

  1. The total energy produced by an array over one day
  2. The temperature of the module backsheet under load
  3. The instantaneous power density of sunlight striking a surface, in W/m² Correct answer.
  4. The angle between the module face and the horizon

Explanation

Irradiance is the instantaneous radiant power per unit area falling on a surface, commonly expressed in watts per square meter. Standard test conditions use 1000 W/m², which is distinct from energy yield and from array tilt.

Question 4Solar PV Fundamentals and Safety

Which meter reading confirms that a string of PV modules is isolated from the inverter before servicing the DC conductors?

  1. A resistance reading across the module frame and ground
  2. A voltage reading of zero at the string conductors after the disconnect is opened Correct answer.
  3. A clamp reading of AC current at the inverter output
  4. A current reading at the combiner showing normal operating amps

Explanation

Verifying zero voltage at the string conductors, using a meter rated for the DC voltage present, confirms the circuit is de-energized at that point. The measurement must be taken at the location where work will occur, not remotely.

Question 5Solar PV Fundamentals and Safety

A technician must select PPE for opening a DC combiner box on a rooftop array. Which document establishes the incident energy and arc flash boundary used for that selection?

  1. The building department's structural permit
  2. The module manufacturer's datasheet
  3. An arc flash risk assessment for the specific equipment Correct answer.
  4. The utility interconnection agreement

Explanation

PPE selection for arc flash exposure is based on an arc flash risk assessment, which establishes incident energy and the arc flash boundary for the equipment. Manufacturer datasheets and interconnection documents do not quantify incident energy.

Question 6Solar PV Fundamentals and Safety

Why does a PV source circuit present a shock hazard even after the inverter and all disconnects are opened during daylight?

  1. The utility backfeeds through the service transformer
  2. Ground fault protection keeps the circuit energized
  3. The modules continue to generate voltage from available light Correct answer.
  4. The inverter stores charge in capacitors indefinitely

Explanation

PV modules produce voltage whenever light reaches the cells, so the source circuit stays energized regardless of switch position. This is why source-circuit conductors must be treated as live and verified before contact.

Question 7Solar PV Fundamentals and Safety

What is the purpose of the rapid shutdown function required for PV systems on buildings?

  1. To balance current between parallel strings
  2. To increase array output during low-light conditions
  3. To disconnect the array from the utility during peak demand
  4. To reduce shock hazard for emergency responders by limiting conductor voltage Correct answer.

Explanation

Rapid shutdown reduces voltage on specified conductors to a safe level for firefighters and other responders operating on or near the building. It is a life-safety provision, not a performance or grid-management feature.

Question 8Solar PV Fundamentals and Safety

A worker is installing racking on a roof with a 6/12 pitch. Which fall protection consideration applies under typical OSHA requirements for residential construction work?

  1. Roof work under 15 feet needs no protection if the pitch is below 8/12
  2. Harnesses are required only when wind speed exceeds 15 mph
  3. Fall protection is required when working at heights of 6 feet or more above a lower level Correct answer.
  4. Fall protection is only required above 20 feet

Explanation

OSHA construction standards generally require fall protection at 6 feet or more above a lower level, and steep roofs have additional requirements. A 6/12 pitch is steep enough that guardrails, safety nets, or personal fall arrest systems are typically needed.

Question 9Solar PV Fundamentals and Safety

Which condition is the most common cause of ground faults in PV arrays that technicians should investigate first?

  1. Miscalibrated irradiance sensors
  2. Failed bypass diodes inside modules
  3. Water intrusion at connectors and damaged conductor insulation Correct answer.
  4. Undersized AC output breakers

Explanation

Moisture intrusion at connectors and insulation damage are leading causes of ground faults because they create unintended current paths to ground. Bypass diode failures and sensor issues do not typically produce ground faults.

Question 10Solar PV Fundamentals and Safety

What does the term 'open-circuit voltage' (Voc) represent for a PV module?

  1. Voltage after the inverter has synchronized to the grid
  2. Voltage measured with the module terminals disconnected and no current flowing Correct answer.
  3. Voltage at the point of maximum power production
  4. Voltage measured while the module is short-circuited

Explanation

Voc is the maximum voltage a module produces when its terminals are open and no current flows. It is used with temperature coefficients to design string voltage limits, since Voc rises as cell temperature falls.

Question 11Solar PV Fundamentals and Safety

A string design must not exceed the inverter's maximum DC input voltage. Which condition produces the highest string voltage and therefore governs the design check?

  1. Modules at the highest expected summer cell temperature
  2. Modules operating at maximum power point
  3. Modules at the lowest expected ambient and cell temperature Correct answer.
  4. Modules at standard test conditions of 25°C cell temperature

Explanation

Voc increases as cell temperature decreases, so the coldest expected condition yields the highest string voltage. Designers apply the Voc temperature coefficient at the record low temperature to confirm the inverter limit is not exceeded.

Question 12Solar PV Fundamentals and Safety

What is the function of a blocking diode in a PV array?

  1. To bypass a shaded module within a series string
  2. To limit the array's open-circuit voltage in cold weather
  3. To prevent reverse current from flowing back into a shaded or lower-voltage string Correct answer.
  4. To convert DC array output into grid-synchronized AC

Explanation

A blocking diode permits current in one direction only, preventing reverse current from the array or battery from flowing back into a lower-voltage or shaded string. Bypass diodes serve a different purpose within a series string.

Question 13Solar PV Fundamentals and Safety

Before energizing a newly installed PV system, which safety check verifies that exposed metal equipment is properly bonded?

  1. Verifying the array's tilt angle against the design
  2. Checking the inverter's firmware version
  3. Confirming equipment grounding conductor continuity from array frames to the grounding electrode system Correct answer.
  4. Measuring open-circuit voltage at each module

Explanation

Continuity testing of the equipment grounding conductor confirms that frames, rails, and enclosures are bonded to the grounding electrode system. This limits voltage differences and supports proper operation of overcurrent and fault detection.

Question 14Solar PV Fundamentals and Safety

What hazard is created by series arcing in a PV DC circuit, and why is it difficult to clear?

  1. The arc only occurs on the AC side of the inverter
  2. The arc extinguishes naturally when DC current crosses zero
  3. Arcing lowers conductor temperature below ignition thresholds
  4. DC arcs do not self-extinguish at a current zero and can sustain until the circuit is opened Correct answer.

Explanation

Unlike AC, DC current has no periodic zero crossing, so a series arc can persist and reach temperatures capable of igniting nearby materials. Clearing requires opening the circuit or otherwise interrupting the current.

Question 15Solar PV Fundamentals and Safety

Which practice best protects a technician from shock while troubleshooting an energized inverter on a sunny day?

  1. Removing gloves to improve dexterity inside the enclosure
  2. Standing on a wet concrete floor to improve grounding
  3. Working with one hand and wearing voltage-rated gloves with insulating tools Correct answer.
  4. Disabling the inverter's ground fault detection during testing

Explanation

Keeping one hand clear reduces the chance of current crossing the heart, while voltage-rated gloves and insulated tools provide an additional barrier. Wet floors and disabling protective functions increase rather than reduce risk.

Question 16Solar PV Fundamentals and Safety

A PV module's nameplate lists a temperature coefficient of power of -0.35%/°C. What does this value indicate?

  1. Power output falls about 0.35% for each degree Celsius above 25°C Correct answer.
  2. Current rises 0.35 amps for each degree above 25°C
  3. Power output rises 0.35% for each degree above 25°C
  4. Voltage falls 0.35 volts for each degree above 25°C

Explanation

A negative power temperature coefficient means maximum power decreases as cell temperature rises above the 25°C reference. The percentage expresses the fractional change per degree Celsius, not an absolute voltage or current change.

Question 17Solar PV Fundamentals and Safety

Why are PV source-circuit conductors often required to be sized larger than the module's short-circuit current alone would suggest?

  1. To carry the 1.25 times Isc continuous-current factor and account for conductor ampacity at high temperature Correct answer.
  2. To eliminate the need for overcurrent protection
  3. To reduce the array's open-circuit voltage
  4. To allow the inverter to operate at a higher DC voltage

Explanation

PV conductors must be sized for at least 125% of the short-circuit current because the array can operate at high current continuously, and ampacity must be corrected for high ambient temperature and conduit fill. Voltage and protection requirements are separate design considerations.

Question 18Solar PV Fundamentals and Safety

What is the primary reason for using a lockout/tagout procedure when servicing a PV inverter?

  1. To increase the inverter's conversion efficiency
  2. To document the service visit for the customer
  3. To prevent unexpected energization of the equipment while work is in progress Correct answer.
  4. To satisfy the utility's metering requirements

Explanation

Lockout/tagout isolates energy sources and prevents another person from re-energizing equipment while a worker is exposed. It is a hazard-control procedure, not a documentation or performance measure.

Question 19Solar PV Fundamentals and Safety

During a site survey, a technician finds the proposed array location partly shaded by a chimney in the afternoon. What is the most appropriate design response?

  1. Relocate the array or use module-level power electronics to mitigate the shading Correct answer.
  2. Oversize the inverter to compensate for the shaded modules
  3. Ignore the shading because bypass diodes eliminate all losses
  4. Connect the shaded modules in series with unshaded ones to average the current

Explanation

Shading reduces string current and can trigger bypass diode activation, cutting output far more than the shaded area alone. Moving the array or using module-level electronics limits the impact to the affected modules rather than the whole string.

Question 20Solar PV Fundamentals and Safety

Which statement correctly describes the difference between a PV module's Isc and its Imp?

  1. Isc and Imp are always identical at any irradiance
  2. Isc is measured with the terminals shorted, while Imp is the current at maximum power Correct answer.
  3. Isc is measured only in darkness, while Imp is measured in sunlight
  4. Isc is the current at maximum power, while Imp is measured with terminals open

Explanation

Short-circuit current Isc is the current that flows when the module terminals are shorted, and it is slightly higher than the maximum power point current Imp. Both are measured under illumination at standard test conditions.

Question 21Solar PV Fundamentals and Safety

What is the purpose of the maximum power point tracking function in a grid-tied inverter?

  1. To limit array current to the module's short-circuit value
  2. To regulate the AC frequency supplied to the grid
  3. To hold the array voltage at the value that extracts the most available DC power Correct answer.
  4. To keep the array voltage fixed at open-circuit voltage

Explanation

Maximum power point tracking continuously adjusts the operating voltage so the array delivers the highest possible power as irradiance and temperature change. It does not fix voltage at Voc or regulate grid frequency.

Question 22Solar PV Fundamentals and Safety

A worker must verify that a string is de-energized at a rooftop combiner. Which meter selection is appropriate?

  1. A non-contact voltage pen as the sole verification tool
  2. An insulation resistance tester alone
  3. A CAT II 300 V rated multimeter for household circuits
  4. A meter and test leads rated for the DC voltage and CAT III or IV environment present Correct answer.

Explanation

Verification requires a meter and leads rated for the voltage present and the transient overvoltage category of the location, typically CAT III or IV for service equipment. Insulation testers and non-contact pens do not provide a reliable de-energization measurement.

Question 23Solar PV Fundamentals and Safety

What role does the equipment grounding conductor play in a PV array with exposed metal racking?

  1. It provides a low-impedance path that bonds metal parts to ground and supports fault clearing Correct answer.
  2. It maintains the array at maximum power point voltage
  3. It replaces the need for overcurrent protection on source circuits
  4. It carries normal operating current back to the inverter

Explanation

Equipment grounding conductors bond non-current-carrying metal parts to the grounding system, providing a low-impedance fault path that allows overcurrent devices to operate. They are not intended to carry normal operating current.

Question 24Solar PV Fundamentals and Safety

Which factor most directly determines the annual energy yield of a fixed-tilt PV array at a given site?

  1. The color of the inverter enclosure
  2. The gauge of the AC equipment grounding conductor
  3. The array's tilt and azimuth relative to the site's solar path Correct answer.
  4. The number of spare fuses kept on site

Explanation

Orientation determines how much irradiance the array receives over the year, so tilt and azimuth relative to the sun's path strongly drive energy yield. Enclosure color, grounding conductor gauge, and spare parts do not affect production.

Question 25Solar PV Fundamentals and Safety

A ground fault detection system trips repeatedly on a large array after a rainstorm. What is the most systematic first step in troubleshooting?

  1. Replace the inverter immediately
  2. Isolate and test sections of the array to locate the faulted conductor or connector Correct answer.
  3. Increase the ground fault trip threshold to stop nuisance trips
  4. Add more modules to the string to raise the operating voltage

Explanation

Sectionalizing the array allows the technician to isolate the faulted string, conductor, or connector before replacing equipment. Raising thresholds or altering the array does not correct the underlying insulation or moisture problem.

Question 26Solar PV Fundamentals and Safety

A PV installer is selecting personal protective equipment before working on the DC side of a residential rooftop system. Which combination reflects standard practice for arc-flash and shock protection on energized DC conductors?

  1. Anti-static wrist strap, nitrile gloves, and a face shield
  2. Rubber dishwashing gloves, a long-sleeve shirt, and a hard hat
  3. Leather work gloves, cotton coveralls, and safety glasses with side shields
  4. Voltage-rated insulated gloves, arc-rated clothing matched to an incident-energy analysis, and eye protection Correct answer.

Explanation

Energized DC work requires gloves rated for the system voltage with a leather protector, arc-rated clothing selected from an incident-energy analysis or the applicable table method, and eye or face protection. Ordinary leather, cotton, or household gloves provide mechanical or chemical protection only and do not insulate against PV DC voltage. An anti-static strap is a electronics-assembly tool and would actually increase shock risk on live conductors.

Question 27Solar PV Fundamentals and Safety

During a rooftop installation, a crew must decide how to handle a module that has a cracked backsheet and visible cell damage. What is the appropriate course of action?

  1. Install it at the end of the string where its reduced output will have the least effect
  2. Cover the module with a tarp and leave it connected in the string
  3. Remove it from the array, isolate it from other modules, and handle it as damaged equipment per the site's plan Correct answer.
  4. Clean the area and continue installation because the glass is intact

Explanation

A cracked backsheet compromises the module's electrical insulation and moisture barrier, creating shock and ground-fault risk, so the module must be taken out of service rather than installed. Damaged modules are typically segregated and handled under the manufacturer's and employer's damaged-equipment procedures. Leaving it connected, even covered, keeps a compromised insulation system in the array.

Question 28Solar PV Fundamentals and Safety

What does the term 'standoff voltage' describe when evaluating a PV module's insulation system?

  1. The voltage the module produces at standard test conditions
  2. The maximum DC voltage the module's insulation can withstand continuously without breakdown Correct answer.
  3. The difference between open-circuit voltage and maximum power voltage
  4. The voltage drop across a bypass diode during forward conduction

Explanation

Standoff voltage refers to the dielectric capability of a module's insulation system, meaning the continuous voltage it can safely withstand between live parts and accessible surfaces. It is a design limit tied to system voltage, not an operating point of the module. Module electrical parameters such as Voc, Vmp, and diode drops are unrelated quantities.

Question 29Solar PV Fundamentals and Safety

A technician is planning to disconnect a DC string at a rooftop junction box on a clear afternoon. Which step should be taken first to reduce hazard?

  1. Cover the string's modules with an opaque material and verify reduced voltage before opening the circuit Correct answer.
  2. Wait until the inverter displays zero output on its monitor
  3. Put on leather gloves and pull the connectors apart quickly to limit arc duration
  4. Open the inverter's AC breaker and treat the DC side as de-energized

Explanation

PV modules generate voltage whenever illuminated, so the DC side cannot be de-energized by opening the AC breaker. Covering the array with an opaque blanket reduces irradiance so the string voltage falls, and the technician verifies this with a meter before separating connectors. Quick separation or relying on inverter display readings does not remove the source voltage.

Question 30Solar PV Fundamentals and Safety

Which statement best describes the shock hazard associated with the grounded conductor in a PV source circuit?

  1. It carries no current under normal operation and can be used as a test reference without a meter
  2. It is bonded to ground at one point but can still carry current and be at a potential above earth during a fault Correct answer.
  3. It is isolated from ground and floats at the array's maximum power voltage
  4. It is always at zero volts and can be touched safely without testing

Explanation

A grounded conductor is bonded to ground at a single point so it normally sits near earth potential, but it is a current-carrying conductor, and an open bond or a fault can raise it above earth. Workers must still test before touching it. It is not a guaranteed zero-volt surface, and it is not floating.

Question 31Solar PV Fundamentals and Safety

A crew is working near the array on a hot, clear day and a worker reports dizziness and headache. Which action matches accepted heat-illness response?

  1. Move the worker to a shaded, cooler area, loosen clothing, provide cool water, and monitor while arranging medical evaluation if symptoms persist Correct answer.
  2. Give the worker a caffeinated energy drink and continue the task
  3. Apply sunscreen and have the worker change into lighter clothing before continuing
  4. Have the worker sit down briefly and then resume work to avoid losing schedule time

Explanation

Heat exhaustion presents with dizziness, headache, weakness, and nausea, and the response is to cool the worker, hydrate, and monitor while arranging evaluation if symptoms do not resolve. Returning to work or masking symptoms with stimulants or sunscreen risks progression to heat stroke. Roof work in full sun is a recognized high-risk setting for heat illness.

Question 32Solar PV Fundamentals and Safety

What is the purpose of a bypass diode in a PV module?

  1. To provide an alternate current path around shaded or damaged cells so they do not overheat or limit string output Correct answer.
  2. To prevent reverse current from flowing back into the module at night
  3. To discharge static electricity from the module frame
  4. To step the module voltage up to the string voltage

Explanation

When cells are shaded or damaged, they can become reverse-biased and dissipate power as heat, creating hot spots. A bypass diode routes current around the affected substring, protecting the cells and preserving most of the string's output. Blocking reverse current and static discharge are different functions.

Question 33Solar PV Fundamentals and Safety

A technician must confirm that a rooftop DC combiner is safe to open. Which measurement approach is appropriate?

  1. Measure DC voltage from each input to ground and between inputs with a CAT III-rated meter and correctly rated probes Correct answer.
  2. Measure AC voltage at the combiner output terminals
  3. Use a non-contact voltage pen as the sole verification method
  4. Rely on the inverter's DC disconnect switch position indicator

Explanation

Verifying a DC combiner requires a meter rated for the system voltage and category, with probes rated for the available fault current, and measurements taken from each input to ground and across inputs. A non-contact tester alone cannot confirm absence of DC voltage, and a switch position indicator shows mechanical state, not electrical condition. AC measurements do not address the DC source circuits.

Question 34Solar PV Fundamentals and Safety

Which factor most strongly increases the arc-flash hazard when a technician opens a DC disconnect under load on a large PV array?

  1. Low ambient temperature at the array
  2. High available DC fault current combined with high system voltage Correct answer.
  3. Use of a disconnect with a higher current rating than required
  4. A short distance between the inverter and the service panel

Explanation

Arc-flash energy rises with both the current an arc can draw and the voltage sustaining it, so large arrays at high DC voltage present greater incident energy at switching points. Ambient temperature, over-rated equipment, and inverter-to-panel distance do not drive arc energy at the disconnect. Opening under load is the condition that initiates the arc in the first place.

Question 35Solar PV Fundamentals and Safety

A PV system uses a central inverter with a DC combiner. Where is the most appropriate location for the DC arc-fault circuit interrupter detection?

  1. At the utility meter socket
  2. Only on the AC output of the inverter
  3. In the inverter or combiner circuitry monitoring the DC conductors, with the trip function interrupting the faulted circuit Correct answer.
  4. On the equipment grounding conductor at the service panel

Explanation

DC arc-fault protection is required to detect series arcs on PV source and output circuits, so detection is placed in the combiner or inverter where those conductors terminate, and the device acts to interrupt the faulted circuit. AC-side or service-panel devices cannot detect DC series arcs in the array wiring.

Question 36Solar PV Fundamentals and Safety

Why are PV source-circuit conductors required to have ampacity at least 125 percent of the module short-circuit current before other adjustments?

  1. Because the conductors must withstand the array's open-circuit voltage
  2. Because the equipment grounding conductor is sized from the same value
  3. Because the conductors must carry the inverter's AC output current
  4. Because modules can produce irradiance-enhanced current above nameplate and the conductors must carry continuous current without overheating Correct answer.

Explanation

PV modules can exceed nameplate Isc under high irradiance and at low temperatures, and source circuits operate continuously whenever the sun shines, so the code applies a 125 percent factor to short-circuit current before applying conditions-of-use corrections. This keeps conductor insulation within temperature limits. Voltage and AC output current are separate design considerations.

Question 37Solar PV Fundamentals and Safety

A crew is trenching for PV DC feeder conductors between an array and a building. Which practice best addresses buried-conductor safety?

  1. Install conductors at the required burial depth with appropriate mechanical protection and mark the route before digging Correct answer.
  2. Bury conductors directly against sharp rock without bedding
  3. Run the conductors overhead on the fence line instead of trenching
  4. Lay conductors on the surface and cover them with loose gravel

Explanation

Buried PV conductors must be at code-required depths, protected against physical damage where they emerge or cross, and the route should be located and marked before excavation to prevent dig-in injuries. Surface-laid or unprotected conductors are exposed to damage and create shock and arc hazards. Overhead routing on a fence is not a recognized wiring method.

Question 38Solar PV Fundamentals and Safety

Which statement accurately describes the behavior of a PV array's open-circuit voltage as cell temperature drops?

  1. Voc decreases as temperature falls because resistance rises
  2. Voc falls to zero at freezing because carrier mobility stops
  3. Voc stays constant because irradiance is unchanged
  4. Voc increases as temperature falls, which is why cold-temperature Voc is used for maximum system voltage checks Correct answer.

Explanation

The open-circuit voltage of a PV cell has a negative temperature coefficient, so Voc rises as cell temperature decreases. Designers use the lowest expected cell temperature to compute maximum string voltage and compare it with equipment voltage ratings. Irradiance affects current far more than it affects the temperature trend of voltage.

Question 39Solar PV Fundamentals and Safety

A technician notices that a string's measured open-circuit voltage is well below the expected value for the number of modules in series. Which interpretation is most reasonable?

  1. The inverter is exporting too much power to the grid
  2. The equipment grounding conductor is oversized
  3. The array tilt is too steep for the season
  4. One or more modules may be bypassed, disconnected, or shaded, so the string should be inspected Correct answer.

Explanation

Open-circuit voltage of a series string is the sum of module voltages, so a large shortfall points to modules that are bypassed, open-circuited, or heavily shaded, or to a measurement taken under low irradiance. The technician should check irradiance conditions, then inspect connections and module states. Inverter export, tilt, and grounding conductor size do not reduce string Voc.

Question 40Solar PV Fundamentals and Safety

What is the primary safety reason for verifying that a PV array's exposed metal racking is bonded to the equipment grounding conductor?

  1. To prevent the inverter from exporting power at night
  2. To improve the array's energy production by reducing static charge
  3. To keep the modules cooler in summer
  4. To provide a low-impedance fault path that lets overcurrent protection clear a fault and limits voltage on touchable metal Correct answer.

Explanation

Bonding exposed metal to the equipment grounding conductor creates a low-impedance path back to the source so a fault trips the overcurrent device quickly, and it holds touchable metal near earth potential during a fault. It does not improve production, cool modules, or control inverter export.

Question 41Solar PV System Components and Electrical Basics

A PV module lists an open-circuit voltage (Voc) of 45.8 V and a temperature coefficient of Voc of −0.29 %/°C. At a record-low cell temperature of −10 °C, what is the approximate corrected Voc?

  1. 41.2 V
  2. 58.0 V
  3. 50.4 V Correct answer.
  4. 45.8 V

Explanation

The correction factor is 1 + (−0.0029 × (−10 − 25)) = 1 + 0.1015 ≈ 1.1015. Multiplying 45.8 V by 1.1015 gives about 50.4 V, which is the value used for cold-temperature string sizing against the inverter maximum input voltage.

Question 42Solar PV System Components and Electrical Basics

Which condition defines the standard test conditions (STC) used to rate PV module power?

  1. 1000 W/m² irradiance, 25 °C cell temperature, AM 1.5 spectrum Correct answer.
  2. 500 W/m² irradiance, 25 °C cell temperature, AM 1.0 spectrum
  3. 800 W/m² irradiance, 20 °C ambient temperature, AM 1.0 spectrum
  4. 1000 W/m² irradiance, 20 °C ambient temperature, AM 1.5 spectrum

Explanation

STC is defined as 1000 W/m² irradiance, a 25 °C cell temperature, and the AM 1.5 reference spectrum. Nameplate watts on a module datasheet are measured under these conditions, not under field conditions.

Question 43Solar PV System Components and Electrical Basics

A string of modules is wired in series. Which statement about the string's electrical output is correct?

  1. Voltage adds and current stays the same as one module Correct answer.
  2. Both voltage and current add
  3. Current adds and voltage stays the same as one module
  4. Both voltage and current stay the same as one module

Explanation

In a series circuit the same current flows through every element, so the string current equals the current of one module while the voltages sum. Series wiring is therefore used to build string voltage up to the inverter's operating window.

Question 44Solar PV System Components and Electrical Basics

Three identical modules, each rated 12 A at 40 V, are connected in parallel. What are the approximate array output current and voltage?

  1. 12 A at 40 V
  2. 36 A at 120 V
  3. 12 A at 120 V
  4. 36 A at 40 V Correct answer.

Explanation

Parallel branches share one voltage while their currents sum, so three 12 A modules give 36 A at the common 40 V. Parallel connection is used when more current is needed at a given voltage.

Question 45Solar PV System Components and Electrical Basics

What is the primary function of a bypass diode in a PV module's junction box?

  1. Provide an alternate current path around shaded cells to reduce hot-spot heating Correct answer.
  2. Block lightning-induced surges on the DC circuit
  3. Step the module voltage down to battery charging voltage
  4. Limit reverse current from the battery at night

Explanation

When cells are shaded or damaged they can be forced into reverse bias by the current of the unshaded cells, dissipating power as heat. The bypass diode provides a parallel path around the affected substring, limiting hot-spot temperature and preserving string output.

Question 46Solar PV System Components and Electrical Basics

A module's nameplate Isc is 10.2 A and the maximum series fuse rating is 15 A. After applying NEC 690.8(A) to size conductors for the array output circuit, what continuous current value is used?

  1. 12.75 A Correct answer.
  2. 10.2 A
  3. 15 A
  4. 8.16 A

Explanation

PV source and output circuits are treated as continuous, so the short-circuit current is multiplied by 125 % before conductor ampacity is selected. Here 10.2 A × 1.25 = 12.75 A, which is then compared against conductor and overcurrent ratings.

Question 47Solar PV System Components and Electrical Basics

An inverter is rated 7.6 kW AC continuous output at 240 V. What is the minimum continuous AC output current used for sizing the inverter output circuit?

  1. 38.0 A
  2. 24.0 A
  3. 19.0 A
  4. 31.7 A Correct answer.

Explanation

Dividing 7600 W by 240 V gives 31.67 A, and the continuous-output rating is what the circuit must carry. Conductors and overcurrent devices are then sized from this value with the applicable 125 % factor.

Question 48Solar PV System Components and Electrical Basics

Which device automatically disconnects the PV array from the inverter and is typically required at the inverter location for service personnel?

  1. Ground-fault detection and interruption system
  2. PV DC disconnect Correct answer.
  3. Rapid shutdown initiator
  4. DC arc-fault circuit interrupter

Explanation

The PV DC disconnect provides a manual means to open the DC conductors between the array and the inverter. It isolates the inverter for maintenance and is separate from rapid-shutdown, AFCI, and GFDI functions.

Question 49Solar PV System Components and Electrical Basics

A utility-interactive string inverter is installed without a battery. What is the inverter's role in relation to the utility grid?

  1. It regulates grid voltage by absorbing reactive power at all times
  2. It rectifies grid AC into DC to charge the array
  3. It creates its own voltage reference and operates independently of the grid
  4. It synchronizes its output to the grid voltage and frequency and ceases output when the grid is lost Correct answer.

Explanation

A grid-tied inverter uses the utility as its voltage and frequency reference, exporting current in phase with the grid. Anti-islanding protection requires it to stop exporting when the grid is de-energized.

Question 50Solar PV System Components and Electrical Basics

What is the main purpose of a maximum power point tracker (MPPT) in a PV inverter?

  1. Adjust the operating voltage to keep the array at its maximum power point as irradiance and temperature change Correct answer.
  2. Limit array voltage to the inverter's maximum input rating
  3. Balance the state of charge between parallel battery strings
  4. Convert the array's DC current into AC current

Explanation

The MPPT continuously sweeps or samples the array's operating point and adjusts the DC bus voltage so the array stays near its maximum power point. Because the I-V curve shifts with irradiance and temperature, a fixed operating voltage would waste available power.