Alltec Corporation News & Articles
Gain Control of your Equipment's Power Quality: Eliminate Critical and Costly Downtime
Product-Spotlight by Alltec Corporation
Monday January 11, 2010
In the technologically progressive world that we live in today, companies rely more heavily than ever on sensitive electronic equipment. Technology is becoming faster, smaller, & more efficient. In exchange for faster speed, however, electronics are becoming increasingly susceptible to surges. In response to this demand Alltec Corporation has created PowerTrip® Surge Protection Devices (SPDs).
PowerTrip® Surge Protection Devices reduce the magnitude of random, high energy, short duration electrical power anomalies. These occurrences are typically caused by atmospheric phenomena (such as lightning strikes), utility switching, inductive loads, and more. Over 80% of transient activity is internally generated, and it is estimated that electrical transients cost US companies more than $26 billion per year in damages and losses. High energy spikes take place and can damage equipment such as computers, instrumentation, and process controllers often without causing noticeable physical damage to components. This can cause system upset, lost data and data lines, erroneous signals and false system operations.
The installation of Surge Protection Devices (SPDs) is essential to reduce the risk of personal injury, physical equipment damage, and loss of operations. PowerTrip® surge suppressors provide ultimate protection for modern sensitive microprocessors based equipment in the harshest of transient environments. These applications are being used in residential homes, telecommunication facilities, information technology buildings, automation controls, oil & gas industries, wind farms, and much more. PowerTrip® SPDs are designed with “Discrete All Mode Protection” to eliminate the transient voltage between all possible modes: L-L, L-N, L-G, and N-G. The ultimate goal of our approach is to keep sites and systems operating safely, reliably,
PowerTrip® devices are available for AC and DC power, telephone/data, and RF cabling protection. Experienced engineers will assist you in choosing the correct product for your application. Our expert installation team will make certain that your products are installed correctly, ensuring that sites and systems are operating safely and reliably.
Surge Suppression Technology
Voltage Responsive Circuit Technology provides the best suppression of high energy impulses and operates at a fixed low let-through voltage. In addition to the fixed system, Frequency Responsive Circuit Technology has thresholds which track the AC & DC sinewave and are able to respond to any transient activity on the system at whatever polarity and phase angle it occurs; it filters all frequency disturbances other than 50/60 Hz. PowerTrip® SPD products are engineered to meet the demanding requirements of countless applications.
PowerTrip ® Features
- Withstands repeated transients
- Quick response and recovery time
- Tight nominal clamping levels
- Frequency Responsive Circuitry and EMI/RFI filtering capabilities
- Surge Counters, Audible Alarms and Dry Relay Contacts
- Array of NEMA rated enclosures
- Fail Safe
- Thermal Insulation
Compliance
• ANSI/UL 1449 3rd Edition Listed and UL 1283 Listed
• IEEE C62.41-2002 and C62.41.2-2002 Tested Standards
• NEMA LS-1 (1992)
Transient Voltage Sources
• Power company & load switching
• Generator switching
• HVAC equipment
• Industrial equipment
• Fluorescent lights
• Elevators
• Switching of inductive loads
• Lightning activity
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The Benefits of Designing and Testing a Low-Resistance Grounding System
Grounding by Alltec Corporation
Wednesday December 30, 2009
We all have become dependent on electronics for our everyday lives. These same sensitive devices are very vulnerable to the hazards created by poor grounding. As any power quality expert will relate, poor grounding is second only to improper wiring as the leading cause of equipment malfunction. Standards for equipment performance mandate the installation and maintenance of a reliable, low-resistance earth ground. These standards often cannot be met and certainly cannot be assured for the long term by traditional grounding methods, which call for minimum requirements. Much of this equipment operates on 5 V or less and is often subjected to higher steady-state transients. A properly designed low-resistance system can ensure the operation of critical equipment that often creates its own hazards, such as harmonics and transients. An additional benefit also comes in enhanced personnel safety.
Earth Grounding
The definition of a ground electrode is “a conductor or group of conductors in intimate contact with the earth for the purpose of providing a connection with the soil.” This definition does not refer to an actual ohm resistance value of the electrode. The resistance value is determined by the resistivity of soil with which these electrodes are in contact. As in the case of ground water, the current must pass through the soil to the assumed earth potential of 0 Ω. When an object is grounded, it is then forced to assume the same zero potential as the earth. If the potential of the grounded object is higher or lower, current will pass through the grounding connection until the potential of the object and earth are the same. The earth electrode is that connection path from the equipment to the earth (Figure 1). The resistance of the electrode, measured in ohms, determines how quickly and at what potential energy is equalized. Hence, grounding is necessary to maintain an object’s potential equal to that of the earth’s.
Figure 1. Ground electrode
Soil Resistivity
The soil is the dynamic conductor for steady-state, natural, and man-made fault currents. Most soils naturally contain varying amounts of electrolytes that conduct electricity. As a result, the addition of moisture will enhance or reduce the conductive properties. In general, however, the greater the moisture contents in soil, the lower the resistivity. Temperature, like moisture, can have a significant impact on resistivity. Soil resistivity varies with temperature, especially when reaching 32 °F (the moisture in the soil freezes and the resistivity increases by almost three times its unfrozen value). This can have a detrimental effect on your clay-or cement-based backfill materials that rely on water as their primary conductor. A carbon-based backfill material will have the advantage of being an all-weather, year-round, low-resistance conductor.
Soil Resistivity Measurements
To determine the conductivity of the soil, a four-point ground meter is utilized (Figure 2). This test requires the user to place four equally spaced auxiliary probes into the earth to determine the actual soil resistance, traditionally in ohms-cm. This test must take place around the entire area to determine the soil value at all locations. This test is done at different spacing, 5 to 40 feet, to determine the resistance value at various depths. This knowledge will aid in the design and implementation of the correct ground system to meet the particular site requirements. Soil values can range from 500 Ωcm with large amounts of electrolytes to over 1 million Ωcm in sandy dry soil.
Figure 2. Measuring soil resistivity – Click here to enlarge
Post-Installation Testing
Once a ground system has been designed
and installed, the verification process begins. This requires the use of a three-point, fall-of-potential, ground-resistance method (Figure 3). This test involves the use of two auxiliary probes placed in the ground in a straight line. The lengths of the conductors from the instrument to these probes are determined by the size of the facility under test. This is traditionally five times the diagonal distance of the grounding system. The test must also be performed before tying into any other ground source. The reason for this is to verify that your system has the designed ground resistance value without influence from outside sources.
Figure 3. Post-installation testing before power is connected – Click here to Enlarge
If the test is performed after the power is connected, the clamp-on ground-resistance tester can be utilized (Figure 4). This involves clamping onto the power neutral between the utility transformer and the site ground. The user Service Box must be aware that a 0.7-Ωreading indicates a continuity loop and not ground resistance.
Figure 4. Post-installation testing after power is tested
Low-Resistance Grounding System Design
The design process for a grounding system begins with a site and power survey of the installation area (Figure 5). The power survey includes bonding and grounding methods of present AC, telecommunications, SPDs, UPS, and many other systems that operate in the facility. A site survey must also include soil-resistivity analysis at several depths, relevant site plans, topography analysis, and a boring core sample, if available. The site survey will show if any physical barriers such as rock, high-resistivity Mode soil, or power lines will affect the earth-ground resistance in the installation area. Once this information is obtained, an effective design can be initiated.
Figure 5. Site and power survey – Click here to enlarge
Benefits of a Well-Designed System
A properly designed low-resistance grounding system will play a major role in obtaining and maintaining a well-protected and efficient facility. High-tech equipment is highly sensitive and business downtime is often irreplaceable. In the fast paced competitive business world availability is everything; to stay at the forefront of hard-line business competition companies must be entirely reliable. The ground system is an integral part of the site and should be regarded as highly as all the other equipment-critical components. This may be achieved with traditional methods and/or an enhanced system with electrolytic electrodes with carbon backfill.
About the Author
Harshul Gupta is the Vice President of Engineering at Alltec Corporation. He has a Master’s in Electrical Engineering and more than 10 years of industry experience. He has extensive knowledge in the design and testing of grounding systems for commercial and industrial facilities. He has written many technical papers on the subject.
Why Protecting Wind Turbines from Lightning is Critical
News by Alltec Corporation
Tuesday December 29, 2009
Exactly when and where lightning will strike is an unpredictable act of nature. If scientists could calculate the exact location of future lightning, the United States would be able to avoid the $2 billion in annual property damage due to this awesome yet terrifying natural phenomenon. However, the fact that lightning usually strikes the highest point is indisputable. Height, shape and isolation are all leading factors in determining the place where lightning will choose to strike. One of the worst possible courses of action during a storm is to stand under a tree; in fact, this is the number one leading cause of death or injury from lightning strikes. Wind turbines act in a similar manner, as they are the tallest point and sustain a high probability of being struck by lightning. Therefore, it is often not a matter of “if” but “when” a wind turbine will be struck by lightning or experiences other types of overvoltages and currents.
Read the full white paper here
View More: News, Lightning-Protection
Protecting Variable Frequency Drives
Articles by Alltec Corporation
Thursday October 29, 2009
Surge Protection Devices (SPDs)
Sophisticated and highly susceptible microprocessor based electronics and data communication networks are integrated across every sector of today’s fast paced business world. Preserving these mission-critical systems from the damages of surges, spikes, and transients ensures that these systems are protected from equipment destruction, disruption in service, and from costly downtime. How to properly stage these SPDs can be as important as actually making the decision to purchase them.
Protection of Drives
The use of various types of drives to control motors is very common. The purpose of the drive is to increase the efficiency or to manage the speed of the motor being controlled. Through various processes and control mechanisms, the drive often reshapes the sinewave to provide a signal to the motor that allows for greater efficiency or varies the frequency of the signal to control the speed of the motor.
Due to the action of the drive, the power quality of the electrical environment can be compromised. That is, the drives can create voltage surges and harmonics on the system.
There are various technologies available that aid in correcting these issues. This application note focuses on applying surge protective devices (SPDs) to a drive system to mitigate the damage that can occur due to voltage surges while considering the effects of the harmonics on the surge protective device.
Application of SPDs
To aid in the description of the application of SPDs to a drive system, please refer to Figure 1.
This figure illustrates a typical drive layout. The incoming power is usually delta configured (3 phases and ground).
Often the incoming voltage is 480 V, but other voltages may be used. The incoming power is usually stepped down to a lower voltage (typically 120 Vac) that provides power to the control circuit. The control circuit contains sensitive electronics. Once the power is acted upon by the drive the output is fed to the motor.
As noted, there are five opportunities for protecting the typical drive system—each are labeled with a circled number and are described below.
Drive Input
Protecting the drive input is an essential step in protecting the drive system. Providing protection at this location prevents surge damage due to events propagated on the electrical system from upstream sources, external events such as lightning and switching surges created by the utility, and the interaction of multiple drives on the same system.
At this location, a parallel connected, voltage responsive circuitry device is appropriate (one without frequency responsive circuitry). Frequency responsive circuitry is not recommended for this location due to the fact that this location is typically more susceptible to impulse transients as opposed to ring wave transients.
Inverter Input
The inverter input is one of the most sensitive and critical areas of the drive itself. It is at this location that care must be taken and the proper survey conducted. You may install a parallel connected, frequency responsive circuitry device provided you have confirmation that within this drive that no additional capacitors have been installed to mitigate harmonic currents.
IF THEY HAVE, then at this location, a parallel connected, voltage responsive circuitry device is appropriate (one without frequency responsive circuitry). Frequency responsive circuitry would not be recommended for this location due to the high harmonic content that necessitated the installation of additional capacitors. Installation of frequency responsive circuitry devices at this location will lead to failure of the SPD.
Control Circuit
The control circuit contains sensitive electronics that can be damaged by the environment created by the drive or by surges from external sources. Protection at this location is essential.
Since this circuit is isolated by a step down transformer and it feeds sensitive electronics, a series connected SPD with frequency responsive circuitry is recommended for this location.
Drive Output
Protecting the immediate drive output is recommended when the length of the connection between the drive and the motor is longer than 50 ft (15 m) or if the connection is routed along an external wall or outdoors.
One reason for protecting at the immediate output when the length of the connection to the motor is long is due to reflected waves that can occur as the signal (often higher frequency) from the output of the drive reaches the motor and is then reflect back and forth between the drive and the motor. This action can create "voltage piling" – the reflected voltage adds to the nominal voltage and other reflected waves. The SPD will aid in reducing the voltage peaks of the reflected waves.
More importantly, if the connection between the drive and the motor extends outdoors, along a path that is exposed to the environment or close to the building’s steel structure, protection at this location is important to diminish the effects of direct lightning or induced voltage surges due to nearby lightning. These surges can cause damage to the drive, even if protection is provided at the motor input.
At this location, a parallel connected, voltage responsive circuitry device is appropriate (one without frequency responsive circuitry). Frequency responsive circuitry is not recommended for this location due to the high harmonic content of the signal due to the normal operation of the drive. Installation of frequency responsive circuitry devices at this location will lead to failure of the SPD. Utilizing a voltage responsive circuitry device at this location will eliminate this possibility.
Motor Input
Protecting the motor input is an essential step in protecting the drive system. Providing protection at this location prevents surge damage due to events propagated from the drive output to the motor input. Providing protection at this location aids in extending the life of the motor as the SPD helps to prevent damage to the windings and bearings of the motor due to surges.
Further, if the connection between the drive and the motor extends outdoors, along a path that is exposed to the environment or close to the building’s steel structure, protection at this location is important to diminish the effects of direct lightning or induced voltage surges due to nearby lightning. These surges can cause damage to the motor, even if protection is provided at the drive output.
At this location, a parallel connected, a voltage responsive circuitry device is appropriate (one without frequency responsive circuitry). Frequency responsive circuitry is not recommended for this location due to the high harmonic content of the signal due to the normal operation of the drive. Installation of frequency responsive circuitry devices at this location will lead to failure of the SPD. Utilizing a voltage responsive circuitry device at this location will eliminate this possibility.
Overall, properly installed surge protective devices reduce the magnitude of random, high energy, short duration electrical power anomalies. These occurrences are typically caused by atmospheric phenomena (such as lightning strikes), utility switching, inductive loads, and internally generated overvoltages. The ultimate goal of our approach is to keep sites and systems operating safely and reliably. PowerTrip® Surge Protection Devices incorporate "Frequency Responsive Circuitry" technology years ahead of any other devices on the market today. Utilizing proprietary electro-chemical encapsulation, PowerTrip® SPDs dissipate large amounts of surge energy to prolong service life.
Signal Reference Grids: Grounding Solutions with Exceptional Results
News by Alltec Corporation
Friday October 2, 2009
Proper bonding and grounding are essential factors in today’s quest for ultimate power quality, and it is critical to have a system that is driven by both safety and performance. Alltec Corporation’s Signal Reference Grids (SRGs) are used around the world in communication/data centers to reduce static and noise and to protect equipment. SRGs are cost-effective, easy to maintain, and very successful at protecting equipment from voltage surges.
The Need for an Equipotential Plane
Electronic equipment is typically affected when there is a potential difference between devices. Proper grounding and bonding of sensitive electronic systems, including computer installations, require careful consideration of all frequencies. Alltec’s SRGs provide an equipotential plane for equipment where all electronic and electrical equipment connected can rise and fall together. These signal reference grids (SGRs) reduce or eliminate high frequency transients by achieving a common ground reference for all equipment within an adjoining area. The equipotential grid significantly decreases potential differences and diminishes current flow, thereby eliminating the adverse affect on logic circuits.
Requirements
Signal Reference Grid installation is normally required when:
- The logic ac-dc power supplies used in the electronic equipment are installed with one of the terminals connected to the equipment’s metal frame. This prevents damage to inter-unit signal units by providing a low-inductance, and hence, effective ground reference for all externally installed AC and DC power, telecommunications, or other signal level line to-ground chassis connected Surge Protection Devices that may be used with the associated equipment.
- The signal-level circuits and logic ac-dc power supply common terminals are OEM dielectrically insulated or galvanically isolated from equipment against recommended practice and are instead connected to an insulated “ground” terminal that is intended for connection to an externally installed signal reference circuit.
- There are actual performance problems occurring with the equipment which can be assigned to common-mode electrical noise; they are used to prevent or minimize damage to inter-unit signal-level circuits and equipment power supplies when a power system ground-fault event occurs.
- Low-impedance return path for RF noise currents
- Containment of EM (noise) fields between their source and the plane
- Increased filtering effectiveness of contained EM fields
- Shielding of adjacent circuits or equipment
- Conductive grid embedded in, or attached to, a concrete floor
- Metallic screen under floor tile
- Ceiling grid above equipment
- Supporting grid of raised access flooring
Signal Reference Grids as Grounding Solutions
The purpose of Signal Reference Grids is to enhance the overall reliability of the signal transfer between interconnected items of equipment by reducing the inter-unit common mode electrical noise over a broad band of frequency. All metallic enclosures, conduit, and ductwork should be bonded to the Signal Reference Grid for it to function properly.
Advantages of a well designed Signal Reference Grid
Forms of available Signal Reference Grids
Alltec Corporation designs and manufactures copper ground grids for grounding applications. Typical ground grids are manufactured from #6 solid copper wire on a 6” spacing or grids can be made from 2” wide soft copper strap on a 24” spacing. All connections are welded with silver brazing or wire grids can be exothermically welded for an additional cost. Copper ground grids are available with a continuous perimeter wire or with extended grid wires for making connections to additional grids.
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