Power Conditioning 101

 

 

Power Conditioners

In an ideal electrical world, all electrical power would be perfect. There would never be any fluctuations, line noise would be eliminated and power outages wouldn’t exist. Even spikes caused by lightning and other situations would be eliminated. Unfortunately, we don’t live in that ideal electrical world.

The reality we face is that our electrical power is rarely as good as we’d like it to be or as good as our electronic equipment needs it to be. Even though equipment operates at reduced voltage levels from line level, converting the line current DC (direct current) and regulating it, the variances and noise that exists on the original line voltage can leak through, degrading the operation of our equipment. While that may not be noticeable on a day-to-day basis, if the equipment is attached to a high quality power conditioner, and the output results are compared, the difference is remarkable.

Power conditioners are used to eliminate the possible irregularities in input line voltage, ensuring that the power which arrives at the equipment is as clean and consistent as possible. There are a number of ways in which this is accomplished, so not all power conditioners are created equal, nor do they all provide the same results.

The Problem

There are a number of different types of problems which we can encounter on electrical lines, affecting the actual power that is delivered to the home or office. These fall into five basic categories:

Noise – Electrical noise can get on a line from a variety of sources, most commonly other electric devices. Motors and fluorescent lights are especially bad for putting noise on lines. This often appears in electrical equipment as static.

Spikes – Spikes are the most dangerous type of electrical line problem. They consist of extremely brief increases in voltage, often lasting only milliseconds. However, they can raise the line voltage by several hundred volts for that brief period of time. Even if the spike doesn’t cause any obvious damage, such as blowing up the power supply of a computer, you can be sure that it has degraded the function of that power supply. Spikes come from lightning or from the restart of a power plant.

Surges – Surges are a lengthy increase in line voltage. By lengthy, we’re talking 2.5 seconds or longer. These do not cause much problem, as they only provide a small voltage increase, which the equipment power supply is usually able to handle.

Sags – Sags are the opposite of surges, a dropping in the line voltage. Small sags don’t cause any more problem for electronic equipment than surges do. However, larger sags, which are commonly referred to as “brownouts,” can make it impossible for electronic equipment to function.

Outages – Outages are your standard loss of power, which are commonly known as “blackouts.” They can last anywhere from a few milliseconds to several days, depending on their cause. Even the shortest of outages usually resets electronic equipment, unless that equipment is connected to an uninterruptible power supply (UPS).

While surges and sags are usually not severe enough to cause problems for electronic equipment, the other categories of electrical line problems can cause problems ranging from a minor inconvenience, to serious damage. They can also degrade the operation of many types of electronic equipment, while still allowing it to operate.

The truth is that most electronic equipment is designed to operate off of a clean electrical power supply. Engineering laboratories typically have these clean supplies, although our homes and offices don’t.

Different Types of Power Conditioners

There are a variety of ways that power line conditioners work, each of which has its own advantages and disadvantages. Many higher end power conditioners employ a combination of these technologies, in order to provide a more thorough filtering of incoming power.

We can break these technologies down into two categories: power enhancers and power synthesizers. Power enhancers work by trying to deal with the incoming power, improving its quality. Power synthesizers use the incoming line current to produce electrical power, which is electrically isolated from the incoming power, providing clean power to downstream equipment.

Surge Suppressors

The most common form of power enhancer is the surge suppressor. These are designed to eliminate transient spikes, making the incoming line voltage safe for the equipment that is attached to it. However, in the process of doing so, any spikes to the surge suppressor damage it. Therefore, although surge suppressors are inexpensive, they do need periodic replacement. If the switch is lighted, and the light goes out, you can be sure that the suppressor needs to be replaced (this doesn’t work for all surge suppressors).

Voltage Regulators

All electronic equipment contains a voltage regulator, which maintains the same operating voltage inside the equipment, regardless of sags and surges in the line voltage. They are not very effective against either spikes or noise.

Isolation Transformers

An isolation transformer is a very effective means of eliminating electrical noise, especially line to ground noise. However, they are not as effective in eliminating line to neutral or line to line noise. One great advantage is that they provide single point grounding within the equipment.

Motor Generators

A motor generator is a power synthesizer that works by having an electrical motor connected to the line voltage. This motor then turns a generator, which provides downstream power. The downstream electrical system is totally isolated from the line voltage, ensuring that it is clean. It can even keep the voltage consistent through momentary power interruptions (10 to 30 seconds). However, this is a very inefficient system, as the electrical line current is converted to mechanical energy, then converted back to electrical energy.

The Difference Between UPS and SPS

While often lumped together as the same thing, standby power supplies (SPS) and uninterruptible power supplies (UPS) operate in a different way. Both types have essentially the same components, although there is one critical difference.

Both a UPS and a SPS have an internal battery, or bank of batteries, which is storing electrical power. There is a battery charger to maintain the battery fully charged and a voltage inverter to convert the battery’s DC voltage back into 120 VAC. In both cases, there is a bypass line and an automatic switch.

The difference between the two is that a UPS powers the equipment to be run (the load) directly from the battery at all times. The automatic switch exists to so that the equipment can receive the line voltage directly, in the case of a problem with the battery or inverter. With a SPS, the electrical equipment receives its power from the line voltage and the automatic switch ensures that power is provided from the battery, in the case of a power outage. So, the automatic switch is the major component that is different between the two. Although the schematic for both devices is almost identical, the diagram shows a SPS. If the automatic switch had been pointing towards the inverter, it would be a UPS.

Generally speaking, small UPS units, such as are bought for homes and offices, are actually SPS units. For most cases, this is adequate, as the switchover time for the SPS is rapid enough to provide continuing service to the equipment that it is providing protection for.

These units will usually also contain a surge suppressor to protect from voltage spikes. By their very nature, they both provide protection from voltage sags and power outages. However, the length of time that they can provide protection from a power outage varies, depending upon the total battery storage capacity and the power load of the equipment that is connected to it.

Although the two units are very similar, the SPS doesn’t provide any protection against line noise. However, due to the isolation of the input and output that a UPS provides, it does provide fairly good protection from line noise. It also provides protection against voltage surges which the SPS cannot provide.

For the best possible protection, a standby generator would be connected to a UPS. In this manner, if the line voltage was interrupted, the generator would start automatically, providing continuous power to the UPS and ensuring that its battery did not discharge. This type of system is used in commercial and government applications, where loss of power to computers and other critical systems could have catastrophic results.

 

Rich Murphy