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Free PVCMS Practice Questions

10 free, exam-style PV Commissioning and Maintenance Specialist (PVCMS) practice questions with answers and explanations. No signup required. Work through them below, then take the full free PVCMS practice test to study every exam domain.

Question 1

During commissioning, a technician performs an IEC 62446-1 insulation resistance test at 1000 V on an array whose maximum system voltage is 700 V. The instrument reads a steady 1.3 MΩ. What is the correct disposition of this result?

  1. Fail the array, since a healthy array must read above 40 MΩ to pass
  2. Record it as passing but flag it as marginal and investigate the cause
  3. Re-test at 500 V, because 1000 V always understates the true resistance
  4. Accept it without comment, as any reading above zero indicates good insulation
Show answer & explanation

Correct answer: B - Record it as passing but flag it as marginal and investigate the cause

Question 2

An IV curve traced on a string shows a normal overall shape interrupted by a distinct step (notch) partway down the curve. Irradiance and temperature are stable and normal. What does this signature most likely indicate?

  1. Uniformly increased series resistance across every individual cell in the whole string
  2. A low plane-of-array irradiance reading that has scaled the entire curve downward
  3. Partial shading or mismatch forcing a sub-string into bypass conduction
  4. A shunt leakage fault collapsing the curve near the open-circuit voltage point
Show answer & explanation

Correct answer: C - Partial shading or mismatch forcing a sub-string into bypass conduction

Question 3

While commissioning a multi-string combiner, a technician is deciding when to verify the polarity of each string. According to the IEC 62446-1 verification sequence, polarity should be confirmed:

  1. Before any strings are interconnected or landed in parallel at the combiner
  2. After paralleling all strings, so the combined reading can be checked at once
  3. Only after the insulation resistance test has been completed on the array
  4. During the owner orientation, once the system has operated for thirty days
Show answer & explanation

Correct answer: A - Before any strings are interconnected or landed in parallel at the combiner

Question 4

A 100 kW DC system delivers 480 kWh of energy on a day when the plane-of-array insolation is 6.0 kWh/m². Using PR = E ÷ (POA ÷ G_STC × P_DC) with G_STC = 1 kW/m², the performance ratio is closest to:

  1. 0.60
  2. 0.70
  3. 0.90
  4. 0.80
Show answer & explanation

Correct answer: D - 0.80

Question 5

A grid-tied inverter repeatedly trips offline on overvoltage during midday peak production, but operates normally in the morning and evening. The DC array tests within specification. The most likely cause is:

  1. A failed insulation barrier allowing leakage current to elevate the readings
  2. Reverse polarity on a single source circuit feeding the affected MPPT input
  3. Voltage rise on the AC conductors and grid at high export pushing past the limit
  4. Over-torqued combiner terminations creating resistance that inflates the voltage
Show answer & explanation

Correct answer: C - Voltage rise on the AC conductors and grid at high export pushing past the limit

Question 6

During corrective maintenance, an infrared scan reveals a single combiner terminal running noticeably hotter than its neighbors, yet the measured circuit current is normal for the conditions. The most likely cause is:

  1. An oversized conductor dissipating excess heat at the point of termination
  2. A loose or under-torqued termination creating high resistance and I²R heating
  3. Low irradiance reducing current below the threshold the lug was designed for
  4. Excessive module open-circuit voltage overheating the combiner busbar itself
Show answer & explanation

Correct answer: B - A loose or under-torqued termination creating high resistance and I²R heating

Question 7

A monitoring platform flags a gradual downward trend on one string. Before any failure or alarm occurs, the technician schedules a site visit to correct it. This intervention is best classified as which type of maintenance?

  1. Corrective maintenance, because a string is being repaired in the field
  2. Reactive maintenance, since the technician is responding to a flag
  3. Preventive maintenance, because it follows the routine service calendar
  4. Predictive maintenance, since data trends drive action ahead of failure
Show answer & explanation

Correct answer: D - Predictive maintenance, since data trends drive action ahead of failure

Question 8

A technician is developing a commissioning protocol and must order the electrical verification steps correctly. Which sequence aligns with IEC 62446-1?

  1. Earthing/bonding continuity, then polarity, then Voc, then current, then insulation
  2. Insulation resistance first, then polarity, then continuity, then Voc, then current
  3. Polarity first, then earthing continuity, then insulation, then current, then Voc
  4. Voc first, then current, then polarity, then insulation, then earthing continuity
Show answer & explanation

Correct answer: A - Earthing/bonding continuity, then polarity, then Voc, then current, then insulation

Question 9

A technician runs a 1000 V insulation resistance test on a PV circuit without first disconnecting a surge protective device (SPD) whose clamping voltage is below the test voltage. What is the most likely outcome?

  1. The SPD reinforces the insulation barrier and yields a higher resistance reading
  2. The test is unaffected, since SPDs remain completely inert until a real surge occurs
  3. The SPD conducts during the test, giving a false low reading and risking damage
  4. The instrument auto-detects the SPD and corrects the displayed value internally
Show answer & explanation

Correct answer: C - The SPD conducts during the test, giving a false low reading and risking damage

Question 10

During a visual inspection, a technician finds a string assembled with cross-mated DC connectors (a male connector of one brand joined to a female of another). What is the correct disposition?

  1. Accept it if both connectors are individually listed and weather-sealed
  2. Replace them with matched, intermateable connectors from a single listing
  3. Re-torque the connection to the higher of the two brands' specifications
  4. Wrap the junction in self-fusing tape and document it as field-modified
Show answer & explanation

Correct answer: B - Replace them with matched, intermateable connectors from a single listing

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