In starting square wave UPS are made. The main problem with square wave UPS are many equipements can not run on this type of UPS. This is beacuse of equipements are made to be run on Sinewave supply.

Thus developement of Sine Wave inverter has started. 

We can check the output wave form by harmonics testing. Square wave UPS produces more harmonics than sine wave.

Below is the harmonic analysis of square wave UPS.

UPS Harmonic Test Report

Date : 25-11-2014

Standard	UL1778 article 49 Harmonic Distortion Test
Instrument Under Test	Square Wave UPS
Company Name	Not Disclosed
Rated Voltage and Load	12 Volt, 50A
Battery Type	LeadAcid
Test Condition	On battery source (Assuming full charged battery source)

 

Load Pattern-

On 20% Load

Load Condition	Voltage	Voltage Harmonics
37.685 VA	219.1 V	33.34%

 

Notes–  

1. THD is 33.4% .
2. First Harmonic is 94.9 % of Vrms.
3. Other harmonics are also high.
4. 3^rd harmonic is 15.4% of Vrms.
5. 5^th harmonic is lower than 3^rd  .
6. 7^th harmonic is also high and 15% of Vrms.
7. 9^th harmonic is 13.1% of Vrms.
8. 11^th ,15^th and 17^th harmonics are also greater than 5%.

On 50% Load

Load Condition	Voltage	Voltage Harmonics
91.206 VA	213.1 V	30.67%

Notes–

1. THD is 30.67 %.
2. First Harmonic is 95.6%of Vrms.
3. Voltage is decreased by 6 Volts.
4. 3^rd harmonic is increased to 19.7%
5. 5^th harmonic is reduced to 3.2%.
6. 7^th harmonic is also reduced to 9%.
7. 9^th harmonic is reduced to 11%.
8. 11^th harmonic is increased to 9.0%.
9. Other harmonics are less than 5%.

On 75% Load

Load Condition	Voltage	Voltage Harmonics
151.98 VA	190.7 V	43.08%

Notes-

1. THD is 43.08%.
2. First Harmonic is 91.9 %.
3. Voltage is decreased by 23 Volts.
4. 3^rd harmonic is increased to 30.7%.
5. 5^th harmonic is increased to 17.9%.
6. 7^th harmonic is increased to 12.3%.
7. 9^th harmonic is reduced to 9%.
8. 11^th harmonic is reduced to 6.8 %.
9. 13^th harmonic is increased to 5.3%.
10. Other harmonics are less than 5%.
11. Harmonics from 25 to 55 are less than 1%.

Summary –

1. Expected
2. On low battery THD increases.
3. THD % of square wave inverter is very high.
4. As load increases first harmonic decreases.
5. 3^rd to 15^th harmonics are affected most.
6. Other harmonics are less than 2%.

Testing Instrument – SPEA-1  

     

Download Harmonics Spectrum Report of Square Wave UPS