KB Category Archives: Machine Tools

Safety Interlocks

NK Technologies’ Current Operated Switches are available in models that will Safety Interlocksswitch 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.

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Drill/Tool Status

Automated drilling machines usually provide fast and accurate holes, that is until Drill/Tool Statusthe 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.

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Welder Tip Dressing

Motor-driven tip dressers are used in conjunction with robotic resistance Welder Tip Dressingwelders 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.

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Isolated Alarm System Interfacing

If an alarm or monitoring system is to be installed adjacent to another, (for Isolated Alarm System Interfacingexample: a municipal hurricane or tornado warning system) it is desirable to tie in to it. This can be achieved by the utilization of an NK Technologies’ Current Operated Switch (The split-core version is ideal for this). The switch simply detects current flowing in a conductor to say the audible or visual alarm providing a fully isolated ‘repeater’ signal. Switches are available for both AC and DC applications.

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Power Factor Correction Control

With ever increasing demands for electrical power the power generating Power Factor Correction Controlcompanies 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.

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Power Transformer Monitoring

Installing an NK Technologies’ Current Transducer over the conductors on the Power Transfomer Monitoringsecondary 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.

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Equipment Ground Fault Monitoring

As we become more aware of occupational health and safety so the need for Equipment Ground Fault Monitoringprotection 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.

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Battery Charging System

Industrial re-chargeable battery systems are used to provide primary power for Battery Charging Systemvehicles and back-up systems for critical equipment, like cell phone base stations and other communications equipment. DC current flows in one direction during charging and in the opposite direction during battery operation. Traditional Current Transformers do not work with DC current and using current shunts has been the solution. The shunt operates by producing a voltage potential across its terminals according to Ohm’s law. It suffers from a number of serious disadvantages:

  • Terminals can rise to the potential of the DC circuit.
  • The signal produced is usually 50-100mV at full rated current and must be isolated and amplified to a higher level signal (typically 4-20mA) to be of use to an industrial monitoring or control system.
  • The shunt dissipates power according to the square of the current flowing through it. This manifests itself as a loss of power or an insertion loss.
    Forget the shunt and instead simply pass the current carrying conductor through the aperture of an NK Technologies’ DC Current Transducer. There is no insertion loss and the 4-20mA signal is fully isolated from both the DC current being measured and the power supply. The bipolar option also accommodates the change in direction of current flow.
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Generator Installations

The need for back-up power for critical loads is becoming more and more Generator Installationsapparent 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.

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Current Transformer Monitoring

C.T.s (Current Transformers) have been used for many years to measure AC Current Transformer Monitoringamperage. 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.

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