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–
- THD is 33.4% .
- First Harmonic is 94.9 % of Vrms.
- Other harmonics are also high.
- 3^{rd} harmonic is 15.4% of Vrms.
- 5^{th} harmonic is lower than 3^{rd } .
- 7^{th} harmonic is also high and 15% of Vrms.
- 9^{th} harmonic is 13.1% of Vrms.
- 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–
- THD is 30.67 %.
- First Harmonic is 95.6%of Vrms.
- Voltage is decreased by 6 Volts.
- 3^{rd} harmonic is increased to 19.7%
- 5^{th} harmonic is reduced to 3.2%.
- 7^{th} harmonic is also reduced to 9%.
- 9^{th} harmonic is reduced to 11%.
- 11^{th} harmonic is increased to 9.0%.
- Other harmonics are less than 5%.
On 75% Load
Load Condition |
Voltage |
Voltage Harmonics |
151.98 VA |
190.7 V |
43.08% |
Notes-
- THD is 43.08%.
- First Harmonic is 91.9 %.
- Voltage is decreased by 23 Volts.
- 3^{rd} harmonic is increased to 30.7%.
- 5^{th} harmonic is increased to 17.9%.
- 7^{th} harmonic is increased to 12.3%.
- 9^{th} harmonic is reduced to 9%.
- 11^{th} harmonic is reduced to 6.8 %.
- 13^{th} harmonic is increased to 5.3%.
- Other harmonics are less than 5%.
- Harmonics from 25 to 55 are less than 1%.
Summary –
- Expected
- On low battery THD increases.
- THD % of square wave inverter is very high.
- As load increases first harmonic decreases.
- 3^{rd} to 15^{th} harmonics are affected most.
- Other harmonics are less than 2%.
Testing Instrument – SPEA-1