NABCEP Inverter Systems 2

Question 1

What is the primary function of an anti-islanding protection feature in a grid-tied inverter?

Accepted Answer

Disconnect the inverter from the grid when utility power is lost

Answer

Anti-islanding protection automatically disconnects the inverter from the utility grid when grid power is lost, preventing the PV system from energizing downed lines and endangering utility workers.

Question 2

A string inverter is rated for a maximum DC input voltage of 600V. On a cold winter morning, the open-circuit voltage of the array measures 620V. What is the most likely result?

Accepted Answer

The inverter may be damaged or its warranty voided

Answer

Exceeding the inverter's maximum DC input voltage can permanently damage internal components and typically voids the manufacturer's warranty.

Question 3

Which inverter topology uses a high-frequency transformer to provide galvanic isolation between the DC array and the AC output?

Accepted Answer

High-frequency transformer-based inverter

Answer

High-frequency transformer-based inverters use a transformer operating at high frequency (kHz range) to provide galvanic isolation while remaining more compact than line-frequency transformer designs.

Question 4

When multiple string inverters are installed in a commercial system, each inverter must have:

Accepted Answer

Its own AC disconnect accessible to utility personnel

Answer

NEC 690.15 requires each inverter to have its own AC disconnect means that is accessible to utility workers for safe de-energization.

Question 5

What does the term 'MPPT range' refer to in inverter specifications?

Accepted Answer

The range of DC input voltages over which the inverter can perform maximum power point tracking

Answer

The MPPT range specifies the DC voltage window (minimum to maximum) within which the inverter's maximum power point tracking algorithm can operate to extract maximum power from the array.

(NABCEP) North American Board of Certified Energy Practitioners Solar Practice Test

(NABCEP) North American Board of Certified Energy Practitioners Solar Practice Test

NABCEP Inverter Systems 2