FAQs

Our supply of electricity cannot be taken for granted because it is far from clean, stable and continuous. Severe weather, interferences, accidents involving electric transmission lines, transmission equipment failure, thefts and vandalism can cause power disturbances.

There are also disturbances resulting from sources within and around your premises such as on-off operation of air-conditioners, photostat machines, printers, switching power supplies, fluorescent lights, arc welders, elevators and so on.

All building electronic systems are designed to be operated from a uniform clean electric supply. If the electric supply becomes disturbed or distorted, the electronic systems may be unstable, sending false signals, even malfunction or suffer damage.

Therefore, just as we need treatment systems to purify contaminants from the tap water and a backup supply from water storage tanks, we also need power line conditioning. Power line conditioner is the general term for UPS, AVR, surge suppressors, VSP (Voltage Sag Protectors) and so on.

For example, the UPS is analogous to the water storage tank in every household as it provides backup power supply in case of blackouts. Similarly, if water pressure is low, we use a water pump to increase its pressure. Therefore, the AVR is the equivalent of the water pump; if the utility voltage is low, it can regulate it to normal voltage.

The utility electric supply is subject to a variety of power disturbances such as:

The descriptions above are based on the original Power Line Conditioning FAQ material.

A power conditioning system can be either simple or sophisticated depending on its specifications and circuit designs. However, it usually consists of the following basic components:

A wide range of equipment is available with claimed features such as joule rating, maximum spike current, clamping voltage, response time, EMI/RFI filtering, attenuation and protected lines.

The original FAQ highlights that a simple surge or spike protector may provide a false sense of security if its protection capability is not properly understood.

Basically, two categories of power conditioning equipment are available:

The choice between power enhancement and power synthesis should consider the severity of disturbances, cost of disruption and required power continuity.

Power synthesizers are generally more complex and costly than power enhancers. They may also be less efficient and require more maintenance.

Power conditioning equipment must be properly understood, installed and maintained. Maintenance availability and equipment cost are also important selection factors.

Power synthesizers can be divided into Motor Generators, Rotary Uninterruptible Power Supplies (UPS) and Static Uninterruptible Power Supplies (UPS).

1. On-Line UPS Configuration

In the on-line configuration, the load is continuously fed by the inverter and the battery is constantly float-charged.

On AC mains failure, the inverter draws energy from the battery. There is no discontinuity in the changeover from AC mains to battery operation.

The on-line UPS exhibits zero transfer time and provides isolation between its input and output.

2. Off-Line UPS Configuration

In the off-line configuration, the load is supplied by AC mains while the inverter remains off-line.

Upon loss of AC mains power, the load is transferred to the inverter, which draws energy from the battery.

Some off-line designs also transfer during overvoltage or undervoltage conditions.

The electronic equipment must be able to withstand a transfer time typically measured in milliseconds.

The original FAQ describes off-line UPS systems as commonly available in lower capacities from 300VA to 3kVA.

3. Hybrid UPS Configuration

In the hybrid configuration, the load is connected directly to the inverter of the UPS without a break, similar to an on-line configuration.

This hot standby technique can exhibit zero transfer time with proper circuit design.

An unpredictable power disturbance can cause serious problems for building electronic systems that depend solely on AC mains supply.

Loss of valuable data and downtime may result in reduced productivity, lost sales and disruption of work.

Solutions to power disturbance problems should include an economic evaluation and consideration of intangible factors.

Power conditioning equipment alone may not always be sufficient. Some power quality problems must also be addressed through practical measures such as preventive maintenance, equipment relocation and electrical rewiring for building electronic systems.