Inverters, Types, Ratings and Energy Supply

Question 1

What is the primary function of an inverter in a solar PV system?

Accepted Answer

To convert direct current (DC) electricity into alternating current (AC) electricity

Question 2

In what form do solar panels generate electricity when sunlight strikes their photovoltaic cells?

Accepted Answer

Direct Current (DC)

Question 3

What is the standard utility frequency in Nigeria that an inverter's AC output must match?

Accepted Answer

50 Hz

Question 4

Which type of inverter operates completely independently of the public utility grid?

Accepted Answer

Off-Grid (Stand-Alone) Inverters

Question 5

What safety action does a grid-tied (on-grid) inverter take during a utility power outage?

Accepted Answer

It automatically shuts down

Question 6

Which type of inverter can manage power from solar panels, batteries, and the utility grid simultaneously?

Accepted Answer

Hybrid Inverters

Question 7

Why are pure sine wave inverters preferred for sensitive electronics like laptops and medical equipment?

Accepted Answer

They produce an AC waveform identical to or cleaner than utility grid power

Question 8

What is a common disadvantage of using a modified sine wave inverter with motorized appliances like fans?

Accepted Answer

They can cause appliances to hum, run hotter, or operate less efficiently

Question 9

For which type of load is a cheap square wave inverter suitable?

Accepted Answer

Simple resistive loads like incandescent light bulbs

Question 10

What does the Surge (Peak) Power Rating of an inverter represent?

Accepted Answer

The maximum power the inverter can deliver for a very short duration to start motorized appliances

Question 11

What are the common nominal DC input voltages for residential inverters?

Accepted Answer

12V, 24V, and 48V

Question 12

What is the standard safety margin percentage recommended when sizing an inverter?

Accepted Answer

20% to 25%

Question 13

Which formula is used to calculate the minimum inverter power rating?

Accepted Answer

$\text{Minimum Inverter Rating (W)} = \text{Total Simultaneous Load (W)} \times 1.25$

Question 14

A household runs 5 LED bulbs (15W each), 1 TV (100W), and 2 standing fans (60W each) simultaneously. What is the minimum inverter rating needed using a 25% safety margin?

Accepted Answer

368.75 W

Question 15

Which formula is used to calculate the daily DC energy supply required by an inverter?

Accepted Answer

$\text{Daily DC Energy Supply (Wh)} = \frac{\text{Total Daily AC Energy Demand (Wh)}}{\text{Inverter Efficiency (decimal)}}$

Question 16

A barber shop has a total daily AC energy demand of 1220 Wh. If the inverter efficiency is 90% (0.90), what is the daily DC energy supply required?

Accepted Answer

1355.56 Wh

Question 17

According to typical parameters in Nigeria, what are the specifications of a 'Small' residential inverter system?

Accepted Answer

12 VDC input, 500W – 1.5kW rating

Question 18

Which of the following applications is typical for a 'Medium' sized inverter system (24 VDC, 2kW – 3.5kW)?

Accepted Answer

Refrigerators, washing machines, and pumping machines

Question 19

When verifying the nominal DC input voltage of an inverter from the battery bank, what mode should the digital multimeter be set to?

Accepted Answer

DC Voltage mode

Question 20

How is the efficiency of an inverter defined?

Accepted Answer

The ratio of AC power output to DC power input, expressed as a percentage

Strong work.

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