UPS is the abbreviation for Uninterrupted Power Supply. Generally, a UPS unit serves as a backup power supply for essential or critical equipment.

We use UPS to avoid sudden power outages, as it provides ample time for the operation to undergo a proper shutdown, or it provides transition time for the generators to start up and kick in.

Users at home will need a UPS system when they use their PCs. Others areas that need UPS systems are Data Centres, Process Backup, Military operations, etc.

A UPS Rectifier converts AC (TNB Power) to DC.

An inverter converts DC (Battery power) to AC.

A UPS battery charger takes a portion of DC to keep the batteries at full charge at all times.

A UPS bypass is a device that allows the load to connect to the utility supply directly if the UPS fail or is under maintenance.

It refers to the inverter:-

•  Online UPS is Inverter supply directly to load
•  Offline UPS, the inverter starts only when utility not presents
•  Line interactive UPS is an offline UPS with an AVR / Line conditioner.

Double conversion UPS involves two conversion to the power supply. The power supply is converted from AC to DC and DC back to AC. This UPS gives reliable output to the load.

There is special type of UPS using DELTA transformer technology that claims to yield power factor 1 (pf).

• 6 pulse rectifier UPS.
• 12 pulse rectifier UPS.
• IGBT (Insulated Gate Bipolar Transistor) rectifier UPS.
• Rotary UPS.

IGBT rectifier technology. It uses the high frequency to rectify the AC to DC.

IGBT rectifier reduces Harmonics substantially and reduces the upsize of upstream components. Hence, reduce initial cost and operation cost.

If the backup system solely depend on battery. We need a large battery bank. This will cost space and higher maintenance cost.

Backup time is the time that battery can support during absence of utility power. It is a pre-calculate time base on the load and type of battery used.

KVA is the apparent power it does not reflect the actual power consume. E.g. You need 12KVA source for a 10KW load provided the power factor (pf) is 0.8.

It is a short form of Kilo Watt and it is the actual electrical power consumed.

Parallel capacity happens when a few UPS units share the same load. E.g. a 120KVA load is using 3 units of 40KVA UPS. Generally this design is intended for scaleable operations.

It is a UPS system that is designed in such a way that ensures that if one of the UPS runs into a problem, the rest of the UPS units have sufficient capacity to continue carrying the overall load.

• 1 + 1 system (Usually 2 units only)
• N + 1 system (Usually 3 units and above)

It is a device that connects the load to the utility without any physical contact mechanism. This is also called a semiconductor device.

It is a bypass using mechanical contact. E.g. Contactor, MCCB, etc.

It is a bypass device that is installed outside of the UPS compartment. It is usually built into an electrical switchboard.

It is a system that employs 2 breakers; one for the rectifier and one for the bypass input.

Double breaker inputs are used for a more reliable power source. If the rectifier and the bypass share the same breaker, whenever there is a short circuit that affects the rectifier and trips the breaker, the bypass will also not be available. Therefore, a double breaker system minimizes the risk of power outage.

The most important component of UPS System is the battery. And a battery has both shelving life and operation life, therefore it needs to be monitored periodically. Secondly, maintenance is required to ensure the ventilation fan is running smoothly.

The semiconductor faces no wear and tear, however the internal ventilation fan does.

Listed below are some common types of battery used in UPS system:
• Lead Acid cell
• Sealed Lead Acid
• Alkaline cell

Because SLA batteries are the most economical and low maintenance solution. Also, SLA batteries do not emit any gas into the environment

• Valve Regulated Lead Acid battery (VRLA)
• Sealed Lead Acid Valve Regulated (SLVR)

One battery bank may consist of a few string of battery which connected in parallel.

Yes, for maintenance purpose and short circuit protection. Besides, each string must have its own breaker.

Between 3 to 5 years. But if there is an overcharge of over discharge it will shorten then life span substantially.

Flywheel system, it replaces the battery bank as well as replace genset battery.

The distortion of waveform compares to the normal sine wave. Measures in % of distortion.

1st, 3rd, 5th … 15th are harmful, and above 39th are least harmful.

It will cause overheat of input transformer or input wires. Besides, I demand more power from utility than required.

• Add passive filter or
• Add active filter or
• Add cancellation transformer
• Upsize input cable and transformer or
• Down size the load

• Types of load
• Amount of load
• IS essential power available
• Software support