Critical Choices for Best Protection
Applying a voltage regulator power conditioner is very simple in most situations. The following are some of the factors to be taken into account. As with any electrical product, care must be taken that all national, state and local codes are observed, that the specifying, installation, operation and maintenance of power conditioners is carried out by qualified individuals or licensed professionals.
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Protection from External Problems
| Step Down - Step Up
Unprotected from Internal Problems
The first rule in applying a Voltage regulator power conditioner is:
Place the power conditioner between the source of the power problem and the equipment to be protected.
A corollary to this rule is:
Placing the power conditioner immediately ahead of the equipment to be protected provides the maximum protection.
The sources of power quality problems can be external or internal or both.
External causes include undervoltage, sags, surges or other problems that are initiated on the electrical transmission or distribution network outside the end user's facility. The main electrical service entrance is the point of entry where these problems come into the facility.
Internal causes tend to be sags and undervoltage created by large electrical loads or loads with high inrush current. Motors, magnets, transformers and welders are examples of internal loads that frequently cause power quality problems that can affect other equipment.
A facility subject to chronic undervoltage because of its location in a large industrial park installs a new, CNC tool. When the new tool starts, the large inrush current depresses the already low voltage to the point that other equipment sporadically malfunctions. This is a typical example of external and internal conditions combining to cause a symptomatic power quality problem.
To most effectively apply a power conditioner, there is no substitute for knowing as much as possible about the exact cause(s) of power quality problems.
Following are some examples, good and bad, for applying a power conditioner.
The red lines indicate poor power delivery
The green lines indicate protected power delivery
The red and green lines indicate power delivery that can be intermittently good and poor.
|Maximum Protection I
This is the optimum application - a dedicated power conditioner in front of each device to be protected. In this scheme, each device is protected from external and internal sources of power quality problems. It also provides the highest degree of reliability because of the multiple units. The downside to this scheme is that it is also the most expensive. Larger units are less expensive (based on $/kVA) than multiple smaller units.
|Maximum Protection II
Here again is the optimum application as loads (B) and (C) are protected from both external and internal power quality problems created by load (A).
|Protection from External Problems
In this frequently used application, a power conditioner is sized to protect multiple loads from external power quality problems. Power conditioner costs are minimized by utilizing a larger single unit. If existing wiring is utilized, this can be the lowest cost application.
The downside is lack of protection from internally generated power quality problems (see next example). This application is used where it is known that there are no large or problematic internal loads. Typical applications include installation at service entrances or ahead of distribution panels.
|Unprotected from Internal Problems
As in the preceding example, a power conditioner is sized to protect multiple loads, but in this case load (A) is a source of an internal power quality problem. Typically, this problem takes the form of a sag each time the load is started. This also serves to illustrate that, while the power conditioner is correcting for external problems,internal problems generated downstream of the power conditioner will go uncorrected. Loads (B) and (C) are protected from the external problems but are at risk from those generated by load (A).
Other Application Considerations
In the context of voltage regulators and power conditioners a bypass may serve two purposes: 1) to divert power around a portion of the unit, or 2) to isolate the unit.
When used in the first case to divert power around a portion of the unit, the bypass may be acting to protect the unit itself from extraordinary conditions or it may be providing power downstream because some portion of the unit is has malfunctioned or is temporarily inoperable. For example, if the batteries in a UPS have become drained to the point that they cannot provide power to the load, many UPS (if capable) may go into "bypass" thereby providing raw, unconditioned power to the load so it can remain on line. Also see Electronic Bypass.
In the second case, generally for larger units, a bypass made up of circuit breakers or disconnect devices is provided so that both the incoming and outgoing "sides" of the power conditioner can be electrically isolated from system. In this situation, the unit can be safely isolated for maintenance purposes while the downstream devices receive unconditioned power to remain on line.
Step Down - Step Up
Some voltage regulators and power conditioners are capable of taking incoming power at one voltage level, 480 volts for example , and providing it at a lower voltage level, like 208 volts, at the output. This ability to "step down" the voltage can eliminate the need for a separate transformer to change the voltage to the proper level for the downstream devices. In some cases, a step up might also useful, and some manufacturers can provide this arrangement.
Single phase voltage regulators and power conditioners have simple input and output connections - generally, two "hot" lines in and two "hot" lines with a new ground coming out. In some cases, a single phase unit might be supplied with a line coming from an extra "tap" on the secondary in order to provide single phase output voltages at two convenient levels, such as 240v and 120v. This arrangement is sometimes referred to as a "split phase".
Voltage regulators and power conditioners in three phase applications typically utilize a "delta" input and a "wye" output which is the most common arrangement in industrial and commercial applications. The "wye" output is particularly useful since it affords the possibility of having the output voltage at two different levels (line-to-line and line-to-neutral) and it provides a new ground reference for downstream devices.