The main purpose of UPS power supply testing

The main purpose of UPS power supply testing is to determine if the actual technical specifications of the UPS meet the requirements for use. Typically, UPS power supply testing involves three categories: steady-state testing, dynamic testing, and routine testing. However, in addition to these, there are other types of tests for UPS power supplies.

Steady-state testing involves testing various parameters at the input and output terminals under conditions of no load, 50% rated load, and 100% rated load. This includes testing phase voltages, line voltages, no-load power consumption, power factor, efficiency, output voltage waveform, distortion, and output voltage frequency.

Dynamic testing is typically performed during load variations, such as load step changes from 0% to 100% or from 100% to 0%. The purpose is to examine the UPS output voltage waveform changes to evaluate dynamic characteristics and energy feedback pathways.

Routine testing involves testing the UPS's overload capacity and battery detection.

In addition to these three categories, specialized testing is necessary for large-scale production of UPS units. Some of these specialized tests include:

1. Voltage regulation under leading and lagging power factor conditions to observe the UPS power supply's stability.

2. Efficiency testing under light loads. High-quality UPS units can achieve efficiencies above 80% under conditions of 25% to 35% of the rated load (lagging).

3. Frequent operation testing, including frequent startup and frequent switching. This is done to test the dynamic and thermal stability of the inverter, phase-locked loop, static switch, and filtering capacitors.

4. Charger startup testing to protect the batteries and avoid excessive impact on the power grid during charger startup. Generally, chargers have current limit startup functions, with transition times of typically 10 seconds or more and current limited to 1/10 of the battery capacity.

5. Testing without battery loading to evaluate the UPS's voltage regulation function. Under load without batteries, the UPS should ensure that the output voltage recovers to within (100±1)% within 20ms. Different UPS units have different designs for this function.

6. Harmonic testing to evaluate the UPS's harmonic performance. Generally, UPS units have a total harmonic component of less than 5%, which can be tested using a harmonic analyzer. Good UPS units can filter out all harmonics below the 11th harmonic and maintain stable waveforms. It is advisable to select UPS units that do not have harmonics below the 11th harmonic.

7. Output short-circuit testing is generally not recommended as it may damage the UPS equipment. Some UPS units may have insufficient output short-circuit protection. If short-circuit testing is performed on a UPS with a bypass power supply, it must be done with the bypass power supply disconnected. Otherwise, when a short circuit occurs, the UPS will limit the current and switch the load to the bypass power supply, potentially burning the fuse of the bypass power supply. This would not reveal the current limiting behavior of the output short-circuit protection and would damage the bypass power supply's fuse, which should be avoided.

Additional tests for UPS power supplies may include temperature protection performance testing, operating temperature testing, vibration testing, withstand voltage testing, battery recharging testing, high-temperature testing, high-humidity testing, reliability testing, and testing with different types of loads. These tests are necessary for formal production, especially in mass production. However, for user evaluation and acceptance of the product, static testing, dynamic testing, and routine testing are generally sufficient.