Square Wave UPS Testing
In starting square wave UPS are made. The main problem with square wave UPS are many equipments can not run on this type of UPS. This is because equipments are made to be run on Sine wave supply.
Thus development of Sine Wave inverter has started.
We can check the output waveform 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
Lead Acid
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% |
Voltage Harmonics Spectrum of Square Wave UPS on 20% Load generated by SPEA-1
Notes:
- THD is 33.4%.
- First Harmonic is 94.9 % of Vrms.
- Other harmonics are also high.
- 3rd harmonic is 15.4% of Vrms.
- 5th harmonic is lower than 3rd.
- 7th harmonic is also high and 15% of Vrms.
- 9th harmonic is 13.1% of Vrms.
- 11th, 15th and 17th harmonics are also greater than 5%.
On 50% Load
| Load Condition | Voltage | Voltage Harmonics |
|---|---|---|
| 91.206 VA | 213.1 V | 30.67% |
Voltage Harmonics Spectrum of Square Wave UPS generated by SPEA-1
Notes:
- THD is 30.67 %.
- First Harmonic is 95.6% of Vrms.
- Voltage is decreased by 6 Volts.
- 3rd harmonic is increased to 19.7%
- 5th harmonic is reduced to 3.2%.
- 7th harmonic is also reduced to 9%.
- 9th harmonic is reduced to 11%.
- 11th 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% |
Voltage Harmonics Spectrum of Square wave UPS on 75% Load generated by SPEA-1
Notes:
- THD is 43.08%.
- First Harmonic is 91.9 %.
- Voltage is decreased by 23 Volts.
- 3rd harmonic is increased to 30.7%.
- 5th harmonic is increased to 17.9%.
- 7th harmonic is increased to 12.3%.
- 9th harmonic is reduced to 9%.
- 11th harmonic is reduced to 6.8 %.
- 13th 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.
- 3rd to 15th harmonics are affected most.
- Other harmonics are less than 2%.