Photovoltaic panels are being installed in greater numbers than ever before. Higher efficiencies, lower prices and government incentives help to increase demand, along with consumer attitudes leaning toward all things "green."
System monitoring will improve performance and one of the key components is monitoring the current output of the panels. The two most practical methods used to monitor the DC current produced are current shunts and hall element based sensors.
While shunts are relatively inexpensive, the installer must cut and terminate the wire on both sides of the shunt, they are more prone to inaccurate outputs as the temperature increases and they need insulated covers to keep personnel away from potentially lethal voltages. The output is also very low, susceptible to interference and must be conditioned to be used by most programmable logic controllers or panel meters. Compare this with the hall element design of NK Technologies' DC current transducers.
There is no need to cut or strip the conductor or to disturb wiring at all with the split core models. These DC current transducers provide very stable, highly accurate output at broad temperature extremes; industry standard output signals with high levels of noise immunity; and complete isolation from the monitored circuit. These features save installation time, reduce the number of components required and make the installation very reliable and safe for inspectors or maintenance personnel.
NK Technologies has been manufacturing non-contact hall element based DC current transducers for over ten years, all made in California. Product refinements and production of thousands of units, with corporate focus on quality and reliability has helped to make NK a market leader. The latest design development is the new DLT series DC current transducer. These models are single range, take less panel space in combiner or re-combiner boxes, and produce a 4-20 mA signal through a two wire loop, using nominal 24VDC in series with the output. As with all loop powered signals, they can be converted to 1-5 VDC or 2-10 VDC by the addition of a field installed resistor across the controller input terminals. The design saves time and cabling costs, as just two wires are used rather than four with previous designs.
ATS Current Transducer/Switch from NK Technologies Named a 2012 Plant Engineering Magazine Product of the Year Award Winner
The ATS Current Sensing Switch and Transducer from NK Technologies has received the Silver award for Electrical Controls in the 2012 Plant Engineering magazine Product of the Year contest. The ATS series is a compact one piece solution that combines a limit alarm with an analog output signal transducer to monitor produced or consumed AC current up to 1200 amps, while magnetically isolating outputs and inputs to maximize safety. An innovative and patent pending rotary switch makes it easy for users to set the trip point. DIN rail mounting simplifies installation and provides an extremely secure mount that is resistant to conductor movement.
"Winners are selected by a vote of qualified Plant Engineering subscribers - the engineers who buy, specify and use these products on a daily basis. They are the most qualified people you can find to understand how new products reduce energy costs, ensure safety and improve productivity on the manufacturing plant floor. That's why the Plant Engineering Product of the Year award is so highly regarded in our industry," says Bob Vavra, Editor, Plant Engineering magazine.
"We are honored that Plant Engineering readers recognize the ATS series as a 2012 Silver award winner," says Philip Gregory, President, NK Technologies. "The ATS is an invaluable preventive maintenance tool for monitoring high AC current loads. With the ATS series users can monitor air handling blowers, pumps, crushers and many other large loads with a single self-contained current switch, and the built-in analog signal helps users identify bearing wear and other mechanical problems before they result in unplanned and costly downtime."
This current sensing switch and transducer is also incredibly easy to use. In fact with the ATS Series all that is required for operation is to snap the unit onto a DIN rail, connect it to a power source and connect the outputs to the controller. In contrast, monitoring high current loads often requires a current transformer sized for the maximum current that will be used and the 5 amp secondary of the current transformer is then connected to a shorting block for safety. The connection then runs from the shorting block to a signal conditioner to produce the analog output proportional to the current, or to a different type of signal conditioner to produce an alarm relay contact. Once these connections are made the controller can be connected to the signal conditioner outputs. It requires a great deal of time to interconnect these components, plus the time expended to adjust the signal outputs to match the primary load characteristics.
NK Technologies has introduced a new line of LED current indicators, complementing their existing portfolio of current sensing solutions for factory and building automation markets. Marketed under the trade name AMPFlasher, ACI Series current indicators offer a simple, safe, and inexpensive way to quickly and clearly see live current carrying conductors. Particularly useful for monitoring the status of heaters, motors or lighting, AMPFlasher current indicators can also help in troubleshooting applications or as a space saving alternative to larger current sensors in control panels and motor control buckets.
"The goal behind the AMPFlasher was to address an everyday need by our customers and improve upon the solutions they had as options," says Robin Shaffer, Vice President of Sales and Marketing for NK Technologies. "We created a device that accurately senses current draw, even for small fractional HP motors, without having to wrap the conductor through the hole multiple times. And to make it as visible as possible from all angles and under all conditions, an LED flasher circuit was the obvious choice."
ACI Series current indicators are ideal for use across a broad range of applications including monitoring AC motor status, confirming heater element operation, identifying power loss, monitoring critical lighting loads, indicating loss of phase, detecting loads or as a visual aid to troubleshooting. Standard AMPFlasher features include a 5/16th inch ID suitable for conductors up to 100A; 500mA set point; flashing red LED; compact 1" package with cable tie for secure mounting; UL 508 Listing and RoHS Compliant certification. Additional options include pigtail outputs for remote mounting of LED or a normally open solid-state relay. All NK Technologies products are made in the USA.
NK Technologies has redesigned and expanded its flagship line of voltage sensing products. VTR Series transducers feature a new, easy-to-mount 36.5mm wide DIN-rail compatible enclosure and expanded models for applications from 120V up to 500V. Additional improvements include a robust transformer design now capable of providing dielectric isolation voltages of up to 3500V - among the highest in the industry for similar products. "Improvements to the VTR are in keeping with our philosophy of offering well-engineered, high performance products for a value-conscious automation industry," says Robin Shaffer, Vice President of Sales and Marketing for NK. "This line expansion enhances our ability to help customers detect surges, brown out conditions, and phase loss, all valid concerns when monitoring and safeguarding equipment and control systems."
"Adding NK Technologies' voltage transducers to our current sensor offering gave us the capabilities to solve a particular customer's problem that resulted in our securing a major project." says Eric Le, Product Manager, Sensors, for Eaton Electrical. "We have been extremely pleased with the performance and reliability of NK Technologies' products and their level of customer service. Standard features of the VTR Series include True RMS sensing, quick response times, a wide range of temperature applications and galvanic isolation between input and outputs. The product line is RoHS compliant with additional agency approvals pending.
NK Technologies introduces ASL Series AC Current Operated Switches. The ASL series features a patent pending and user-selectable linear setpoint adjustment, enabling users to reliably monitor current, simply, in a wide range of applications.
The ASL series is available in a panel mounted solid- or split-core enclosure to simplify installation. An easily established contact actuation point can be set with no load present and a two second delay ignores motor inrush current upon energization. Magnetically isolated output maximizes safety and eliminates insertion losses, and solid-state reliability eliminates periodic maintenance or calibration requirements. No external power source is required for operation.
"Current monitoring helps ensure that applications operate at the desired current level, while enabling users to take corrective action before more significant and costly problems resulting from over or under-voltage conditions can occur," says Philip Gregory, President, NK Technologies. "The ASL series provides a current-operated solid state contact that is powered from the monitored circuit. It is unique in that the trip point adjustment uses a single turn potentiometer, meaning the installer can quickly and easily set the point at which the output changes state when the monitored circuit is not energized by simply turning the adjustment arrow to the current magnitude needed."
The ASL series is ideal for monitoring AC motor loads up to 150 amps. With the ASL series users can set a normally open contact over the normal running current level and it will open if the drive belt breaks or comes off the sheaves, or they can set a normally closed contact below the normal run current level to open on over-load conditions. The ASL series is also a perfect solution for monitoring critical lighting loads such as security lighting and water navigational indicators, as well as heating loads by monitoring drying and curing processes remotely and providing independent verification that an element is working properly.
The new CTRC AC Current Transformers from NK Technologies monitor circuits up to 2000 amps and produces a safe, low voltage output proportional to the RMS current value. This output is designed as an input to a power monitor or transducer, replicating the AC wave shape with phase angle resolution better than 2°. The flexible coil design allows the cable to surround multiple conductors or bus assemblies regardless of shape and eliminates the magnetically permeable core of standard current transformers while providing excellent isolation, sensing only the magnetic field of the phase inside the loop. The CTRC can be used in any power monitoring application.
CTRC Current Transformers use the Rogowski coil as the first step in power monitoring. Each coil is matched with a signal integrator, and the output is calibrated for the highest degree of accuracy possible. The resulting 1/3 volt at full range current mirrors the primary circuit wave shape with less than 2° difference in the phase angle and overall linearity of better than 1% of the full scale output. When matched with the circuit voltage wave shapes, a highly accurate representation of the system power, measured in watts, can be derived.
The signal integrator is housed in a compact, DIN-compatible enclosure, with 1.5 meter (59 inches) of lead cable from the sensing loop to the integrator. The signal integrator is powered with 24 volts, AC or DC, consuming less than one watt each. The narrow dimension of the lead cable (0.87 inches) allows for installation in very close quarters, easily possible between the monitored conductor and the adjacent phase. The coils are rated to 600 VAC and do not require shorting blocks between the integrator and the connected load. Even when the current through the loop exceeds the design range, the low voltage output remains at non-hazardous levels.
NK Technologies introduces the APN Series Power Monitoring Sensor. The APN Series Power Monitor measures three phases of current and voltage and computes fourteen values necessary to track power usage in the RS485 Modbus RTU format. The monitor uses current transformers to measure the amperes. The line voltage connects directly to the transducer, up to 600 VAC.
"This sensor is a big step forward from analog signal reporting watt consumption to a digital format allowing information on the system voltage, current, and power factor along with wattage," says Philip Gregory, President, NK Technologies. As the cost of electrical power increases, the desire to use less energy also increases and the need to measure power consumption becomes a necessity, explained Gregory.
Electrical energy is measured in watts over time. To measure watts in an alternating current circuit, the supplied voltage is compared with the current, and whether the current peaks before the voltage (leading power factor in a mostly reactive circuit) or the current peaks after the voltage (lagging power factor in a more inductive circuit), the real power is measured.
"Electronic Smart meters" are used to measure watts, but they only provide information about the entire service consumption. To monitor individual loads or processes, watt transducers or power monitors can be installed. The purpose is to obtain information to help isolate potential problems such as phase loss or voltage sags and voltage spikes, unbalanced current phase to phase, and can help avoid utility surcharges levied for poor power factor.
The APN's RS485 Modbus RTU format is compatible with many programmable logic controllers and fits seamlessly into industrial communications networks, both hard wired and wireless depending on the specifics of the application. The APN can be configured to accept standard 5 amp current transformer inputs or sensors producing 333mVAC proportional to the AC current of the circuit, or they can use factory matched Rogowski coil inputs. The primary circuit voltage is connected directly to the monitor for 600 VAC or lower, or through a potential transformer for monitoring circuits of higher potentials.
The APN is powered from an external supply, improving measurement accuracy of the measurement data. The APN series also provides a pulse contact to open and close as watt hours are accumulated. This feature allows for a less complex data acquisition device for applications where the need to monitor circuit voltages or the other data points is minimal.
New Limit Alarm Current Sensing Contact Switch Offers Easy Adjustment for Quick Setup and Improved Safety
NK Technologies new ASD Series Current Sensing Switches provide a limit alarm contact with the easiest adjustment method ever designed. These current sensing switches feature a single turn potentiometer, allowing the trip point to be set before the sensor is installed or before the monitored circuit is energized. In conjunction, the ASD features an LED display for quick visual indication of where the contact changes, making the ASD the easiest and most accurate setpoint adjustment available. This easily adjustable and precise setpoint simplifies and expedites startup and improves safety by allowing trip point adjustment, with no power through the sensing window.
Compared to alternative technologies, the ASD current sensing switch is the ideal sensor for simplicity, easy installation, and reliability. Common ASD sensor applications for monitoring, detection and control include: conveyor system jam, overload, multiple section interlock integrity; pump system loss of head pressure (open discharge line, pump runs dry, etc.); cooling towers and similar fan handling systems (over- and under-current conditions caused by open duct access door, broken drive belt or coupling, etc.).
ASD sensors are compatible with most automation systems. They provide either N.O. or N.C. magnetically-isolated solid-state output switching for control circuits up to 240 VAC (1.0 amp max). Units are offered with a choice of 0-10 or 0-200 analog setpoint ranges. All units are equipped with an external 24 VAC/VDC power supply for higher accuracy performance with just <2 VA consumption. ASD sensors have a UL94 VO flammability rated case. Operating temperatures are -4 to 122°F (-20 to 50°C) with 0-95% RH, noncondensing. All ASD units are designed for UL, CUL and CE Approval.
The new DT Series 3-Wire DC Current Transducer from NK Technologies is specifically designed in a compact, space-saving case. The DT 3-Wire uses a common point for both power supply and output signal, and is factory calibrated for a single current range. This 3-wire method for DC current measurement keeps costs in check for projects where many sensors are needed.
"Reliability is key in all monitoring applications, and there are gains in reliability whenever the number of connection points can be reduced," explains Philip Gregory, President, NK Technologies. "With the addition of this new series of sensors, NK Technologies has provided the system designer even more choices to measure DC current."
The DT 3-Wire features industry standard outputs of 0-5 or 0-10 VDC proportional to the DC current. It is powered by 24 VDC, factory calibrated, and compact and easy to install. It's commonly used in applications like photovoltaic panel monitoring, hoists, DC motor protection and wind driven generators. The DT Series complements NK Technologies' existing DLT Series of 4-20 mA current output sensors. When specified controllers can read only voltage output sensors, the DT 3-Wire provides the same space saving properties without the need to add an external dropping resistor, consequently removing another place where trouble could occur.
Seamlessly Convert a CT Signal to a Standard 4-20mA Output with New CTC Signal Converters from NK Technologies
NK Technologies introduces CTC Series Signal Converters. With the CTC series users can utilize an existing standard 5 amp secondary CT or low voltage (0.333 VAC) ProteCT current transformer with non-contact ranges as low as 0-5 amps over a conductor to produce a standard 4-20mA two-wire, loop-powered signal. With DIN rail mounting and a 24 VDC loop-powered supply, the CTC series provides simple snap-in installation that requires no calibration because the primary current transformer ratio provides the scaling required without any installer intervention.
"The CTC makes life easier for users who need to monitor current in applications where it is impossible to install a one-piece sensor," says Philip Gregory, President, NK Technologies. "And because the sensor output is industry standard, two and one piece solutions can be mixed in the same controller cabinet."
In some applications, such as monitoring a high voltage system, using a two-piece solution consisting of a current transformer and separate signal converter works better than using a one-piece sensor. A two-piece solution is also a better choice when the system is supplied with bus bars, making installation of a standard NK Technologies one piece current sensor over the conductor extremely difficult or even impossible.
"In a two-piece solution the secondary of a standard 5 amp current transformer is connected to the input terminals of the CTC device, the CTC secondary is connected to a nominal 24 volt DC supply and then to the PLC or panel meter input. The converter then produces 4mA when there is no current through the primary CT, and 20 mA when the CT has full range current present," explains Mr. Gregory.
The AHF 005 & AHF 010 are advanced harmonic filters, not to be compared with traditional harmonic trap filters. The Danfoss harmonic filters have been specially designed to match the Danfoss frequency converters. By connecting the Danfoss harmonic filters AHF 005 or AHF 010 in front of a Danfoss frequency converter, the harmonic current distortion generated back to the mains is reduced to a minimum.
The Integrated Stateful Inspection Firewall is used to control incoming and outgoing traffic on all router interfaces (LAN, WAN, UMTS, VPN tunnels) on both Layer 2 (Ethernet frames) and Layer 3 (IP-based). An "auto-learning" function ("SecureNow!" ) is also incorporated; this performs an automatic analysis of network traffic and generates a set of rules, which the user can then apply or modify as needed.