NK Technologies’ Current Operated Switches are available in models that will switch at measured currents from just a few milliamps (mA) to over 100 amps. Detecting current flow is the definitive measurement to determine if equipment is on or off, a motor is running or not, a heater is on or off etc. NK’s Current Switch products are installed for interlocking for operational and safety purposes.
KB Category Archives: Metals
Automated drilling machines usually provide fast and accurate holes, that is until the drill bit breaks. The last thing a high production furniture manufacturer wanted to do is to keep drilling parts with one hole missing! NK Technologies’ Current Operated Switches were installed over the current carrying conductor feeding the drill motor and when the amperage dropped below a preset level a signal was sent to the controller to stop operation so that the drill bit could be changed. NK’s range of current transducers are used in a variety of applications on machine tools to detect status.
Motor-driven tip dressers are used in conjunction with robotic resistance welders in a manufacturing area like an automobile body assembly plant. Essentially they are like large pencil sharpeners and they require regular maintenance. After maintenance the dressers are not always switched back on, so that when the robotic welder requests tip sharpening, the tips are not dressed and poor quality welds result, which in turn produces poor quality panels. By installing an NK Technologies’ Current Operated Switch on the tip dresser the status is signaled and an alarm is generated to warn if the dresser remains un-powered and offline. NK’s unique split-core packaging is ideal for retrofit installation and the compact solid-core unit is well suited for OEM applications.
With ever increasing demands for electrical power the power generating companies are beginning to penalize customers with low Power Factors. Low PFs can be considered very inefficient use of electrical energy. A low PF can be corrected by the installation of PF Correction capacitors. Although this can be achieved at the main feeder most facilities, due to multiple varying loads, choose to install PF correction on individual pieces of equipment (like a large motor) or area of plant. When a load is switched off, unless the PF correction capacitors are removed, undesirable over-correction occurs. Sophisticated automatic control systems are available but are very expensive. A simple way to switch a PF correction capacitor bank is to use an NK Technologies’ Current Operated Switch. When the load goes down, for example at night when equipment is not used, the PF correction capacitor is switched out. Then when load returns it is switched back in.
Installing an NK Technologies’ Current Transducer over the conductors on the secondary of a transformer can be used to alarm if the current draw reaches a critical level. Action can then be taken to reduce the load before the transformer overheats.
Most large power transformers utilize auxiliary cooling fans, drawing cooler air from a distance away from the transformer. NK Technologies’ Current Transducers or Current Operated Switches are used to monitor these fans for overload from bearing failure, under loads from drive component breakage or slippage, and to just be sure that the fan is energized and doing its required job.
As we become more aware of occupational health and safety so the need for protection against ground faults is growing. Industrial electrical equipment is fed via a distribution system which in turn is connected to a main feed. Ground fault protection may be installed, for instance at a main breaker, protecting the branch circuit but not necessarily a valuable or critical piece of equipment. Industrial Ground Fault Sensors from NK Technologies are designed to be installed in individual pieces of equipment or their electrical feed. The sensors provide an on/off output that may be used to operate a circuit interruption device like a shunt trip breaker or feed into an alarm system. With over 100 models to choose from, there’s sure to be one to fit your application.
The need for back-up power for critical loads is becoming more and more apparent to operating and maintenance personnel. Many existing factories and facilities are also adding generators to assist the grid connection supply during times of excessive consumption, or to help the plant ride through periods of peak usage when the utility charges a premium for power. Monitoring the current demand provided from a generator allows for load shedding of non-critical loads when the generator is nearing its capacity. NK Technologies’ Current Operated Switches close when the demand, measured by current, is too high, and by connecting to a controller (like a PLC), less critical loads can be disconnected from the system.
C.T.s (Current Transformers) have been used for many years to measure AC amperage. There are many C.T.s installed throughout Electric Utilities, Process Plants and Manufacturing facilities. Typically a C.T. provides either a 1A, or more commonly a 5 Amp AC output on the secondary side. In order to use this signal for a modern control system (DCS, PLC or DDC) or Data Logging System a signal conversion or conditioner device is required to provide an analog DC signal.
C.T.s step down current and the secondary has to feed into a very low impedance to maintain accuracy. In the event that the secondary is open-circuited during operation the device operates as a step-up voltage transformer since there is nowhere for the current to flow and voltages of several kV appear on the secondary, overheating occurs and combustion or explosion often results. NK Technologies’ Split-Core Current Transducers are simply and safely snapped over the shorted secondary of a C.T. to provide a fully isolated analog 4-20mA DC signal proportional to the current in the secondary, which in turn is proportional to the measured (primary) current.
NK’s Split-core Current Transducers are used to safely monitor the secondary of high voltage C.T.s used in power generation and distribution in the low voltage cubicles.
Industrial electrical heaters are prone to ground leakage due to the breakdown or contamination of insulators. The use of NK Technologies’ Ground Fault Sensors enables early detection of leakage Currents as small as 5mA. The on/off output of the sensor can be used to trigger a circuit interruption device (for example a shunt-trip breaker) or a monitoring device like a PLC to determine the required action. Latching and auto-reset models are available in both normally energized and normally de-energized configurations suitable for most applications.
The detection of a single phase heater failure by measuring the temperature is like measuring the effect rather than the cause. By installing an NK Technologies’ Current Operated Switch heater failure can be detected before cooling has had time to occur. The signal from the current sensor can be used to switch on a back-up heater, stop the equipment, alarm the equipment operator or trigger the appropriate action.
For 3-phase heaters installing an NK Technologies’ Current Transducer on each leg of a delta connected heating array is the best way to detect loss of one element. Unlike a typical induction motor, there will not be a substantial change in the current draw of the two adjacent phases when a heating element open circuits. The load has disappeared, and the work of heating will not be shared by the other elements. There will be a reduction in thermal output, which can take quite some time to detect with temperature sensors like thermocouples. A current transducer will identify the problem in milliseconds! Poor product quality can be prevented and large quantities of raw material can be saved by quick action.