NETA Battery and UPS Systems Testing 5

Question 1

Which NETA MTS test verifies that a UPS static transfer switch correctly transfers the load to bypass within the specified time when output voltage deviates beyond tolerance?

Accepted Answer

Automatic transfer time test

Answer

The automatic transfer time test confirms the static bypass switch operates within manufacturer-specified milliseconds when UPS output falls outside the acceptable voltage or frequency window.

Question 2

Nickel-cadmium (NiCd) stationary batteries require a different maintenance approach than VRLA batteries primarily because NiCd cells:

Accepted Answer

Require electrolyte level checks and periodic water additions

Answer

NiCd batteries use a liquid potassium hydroxide electrolyte that can deplete through gassing, requiring periodic inspection and distilled water additions unlike sealed VRLA designs.

Question 3

What does the 'C-rate' designation C/8 mean when applied to a battery discharge test?

Accepted Answer

The battery is discharged at a current equal to its rated capacity divided by 8, over an 8-hour period

Answer

C/8 means the discharge current equals the rated ampere-hour capacity divided by 8, resulting in a complete discharge over approximately 8 hours under ideal conditions.

Question 4

During UPS commissioning, the input current total harmonic distortion (THD-I) is measured at 28%. Which standard provides the limits that should be used to evaluate this result?

Accepted Answer

IEEE 519

Answer

IEEE 519 establishes harmonic current and voltage distortion limits at the point of common coupling for power electronic equipment including UPS systems.

Question 5

A VRLA battery float voltage is found to be 0.05 V/cell above the manufacturer's recommended maximum. The long-term consequence of operating in this condition is:

Accepted Answer

Accelerated water loss, dry-out, and thermal runaway risk

Answer

Chronic over-voltage on VRLA cells drives excessive electrolysis, depleting the recombination capacity, drying out the separator, and increasing thermal runaway susceptibility.

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

(NETA) InterNational Electrical Testing Association Certified Technicians Practice Test

NETA Battery and UPS Systems Testing 5