UPS

Question 1

What is a UPS used for?

Answer 1

Supplying critical loads with clean and conditioned power

Question 2

List the 3 major components of a UPS System

Answer 2

Rectifier (input)
Battery Bank (input)
Inverter (output)

Question 3

What connects the 3 major components of a UPS System?

Answer 3

DC Link or DC Bus

Question 4

What are the 3 operation modes of a UPS?

Answer 4

Normal
On-Battery
Bypass Mode

Question 5

During normal mode, what two functions does the rectifier serve?

Answer 5

Provides DC to charge the batteries.
Provides DC to the inverter.

Question 6

What happens during On-Battery Mode?

Answer 6

There is no AC Input at this time, the battery bank is the source.

Question 7

What happens during Bypass Mode?

Answer 7

Utility supply is connected directly to the critical load.

Question 8

Is the output voltage in Bypass mode clean and conditioned?

Answer 8

No

Question 9

What is the normal battery operation time in a UPS System?

Answer 9

5 - 30 minutes

Question 10

Do the batteries in a UPS System change from charging to discharging immediately when the supply fails?

Answer 10

Yes

Question 11

What are the components in a fully redundant UPS?

Answer 11

Two full UPS Systems
Output Transformer
Bypass Switch

Question 12

What are the components in a partially redundant UPS?

Answer 12

Rectifier
Battery Bank
Inverter X2
Output Transformer
Bypass Switch

Question 13

What cct is required for a safe transfer to Bypass mode?

Answer 13

Synchronous Check

Question 14

What are the components of the Bypass Switch?

Answer 14

Anti / Inversely Parallel SCR’s being constantly gated.

Question 15

Why is the maintenance bypass system a Make-Before-Break?

Answer 15

So there is no power interruption during the transfer.

Question 16

How many primary and secondary taps are in the output transformer of a fully redundant UPS system?

Answer 16

Primary = 3
Secondary = 1

Question 17

What is the purpose of an inverter?

Answer 17

To convert DC to AC and create cleaned and conditioned power.

Question 18

What is the most common type of inverter?

Answer 18

PWM (pulse with modulation)

Question 19

What kind of waveform is produced by a PWM inverter?

Answer 19

Sqaure waveforms through a transformer that result in a synthetic sinewave.

Question 20

During inverter operation, switch Q1 and Q4 are __________ and Q2 and Q3 are __________

Answer 20

Q1 and Q4 are positive
Q2 and Q3 are negative

Question 21

What are the 3 applications of an inverter?

Answer 21

UPS
VFD
Phase Converter

Question 22

What type of battery is used in a UPS system?

Answer 22

Lead Acid

Question 23

Lead Acid batteries are divided into 2 groups. What are they and their life span?

Answer 23

Sealed 5 - 10 years
Ventilated 10 - 15 years

Question 24

What is the ideal temperature for a battery to operate?

Answer 24

20 - 25 degrees C

Question 25

What precautions need to be used when testing vented batteries of a UPS System?

Answer 25

Insulated tools
Face shield
Gloves

Question 26

What test would be preformed to indicate battery storage capacity?

Answer 26

Battery discharge test.

Apply a dummy load to the UPS output and remove the power supply while the UPS is operating. Check the DC current reading on the display panel. The reading must indicate a discharge condition with a negative value.

Question 27

Give examples of auxiliary equipment.

Answer 27

Cooling fan
Display screen
Air filter

Question 28

What are the 3 steps to a Load Transfer Test?

Answer 28

1. Manual transfer test
2. Simulating Inverter Failure
3. Overload the UPS

Question 29

What must be done to test the rectifier in the UPS?

Answer 29

The rectifier must be isolated.