Equipment Ground Fault Monitoring
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.
Insulation Breakdown
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.
Heater Life Prediction
As an electric heating element ages, its resistance also changes. Many high 
technology and extreme temperature applications employ exotic and expensive elements. Where the value of the products or materials being heated is high, the failure of a heater or heating element has a financial impact resulting from either reduced quality or scrapped materials. By measuring the current drawn by the element using an NK Technologies’ Current Transducer the resistance of the element can be determined and compared against a known ageing characteristic. When the element reaches a predetermined state it can be replaced prior to failure i.e. predictive maintenance. NK Technologies’ Current Transducers are used in conjunction with intelligent PLC systems when high power SCRs (also known as thyristors) or triacs are installed.
Vacuum Pump Monitor
Vacuum pumps are used in a variety of applications in the semiconductor industry, 
heat treatment, plastics and packaging industries. By adding an NK Technologies’ Current Transducer over the lead feeding a vacuum pump, it can easily be determined when all the air has been removed from a vessel or envelope. The analog output can signal the vacuum or equipment controller that it is time for the next step in the process. In the case of an automated packaging machine, a drop in current will signal that the package is ready for sealing.
Pump Load Monitoring
NK Technologies’ Current Transducers are used to monitor motor current and 
therefore motor load. The output from the transducer may be fed to an analog or digital indicator or a Programmable Logic Controller (PLC) for more sophisticated monitoring and control.
NK Technologies’ Power Transducers provide load monitoring in more critical applications where the addition of voltage measurement and the determination of the phase relationship between current and voltage (power factor) provides more control.
NK Technologies’ Ground Fault Sensors keep the pumps safe by measuring ground leakage currents as low as 5mA. This also provides an alternative to moisture sensors used with submersible pump motors.
Also see these other articles:
Pump Jam & Suction Loss
Moisture Ingress on a Submersible Pump Motor
Status Alarming
The auxiliary contacts in a motor starter are commonly used to indicate when the 
motor is running. However, auxiliary contacts only indicate the position of the contactor, not the actual load status. If a downstream disconnect is open (for example, for maintenance) or the contact fails (either sticks or dirt build-up) there can be serious consequences.
At a large fish farm, failed aerator pumps resulted in massive stock losses. Because the auxiliary contacts remained closed when the pump failed, the alarm was never activated, the back-up pumps were not switched on and the fish suffocated due to lack of oxygen. Now NK Technologies’ Current Operated Switches have been installed to provide an alarm signal and a signal to automatically switch over to the back-up aerator pumps.
Closed Loop Control
Normal linear AC induction motors have a current characteristic that increases with 
load. Thus a measurement of current is proportional to the motor load. NK Technologies’ True RMS Current Transducers are designed to work in conjunction with variable frequency drives (VFD) and measure the current in the leg of the motor.
At an engine block manufacturing facility NK Technologies’ Current Transducers provide the input to a PLC used to position the rotating wire brushes in order to clean away burrs and debris after machining. As the current, and thus the load, changes so the brushes are positioned for optimal clean-up. Similarly Power Transducers are used to control the position of wheel wash brushes in a carwash. Power measurement provides a more linear relationship for motors and other loads with non-linear current characteristics. Current Operated Switches are used to co-ordinate operations between conveyor, washing and drying systems.
Conveyor Jam Protection
When conveyors jam and the drive motor continues to run, expensive mechanical damage to the drive components often occurs. By installing an NK Technologies’ Current Operated Switch an overload condition, detected by higher than normal running amps, can be used to switch off power to the motor before mechanical damage results. The switch setting can be adjusted so it is not affected by normal changes in conveyor load. Current operated switches are the modern day equivalent of less reliable electromechanical jam relays that have been in use for many decades.
In situations where there may be large variations in load an NK Technologies’ Current Transducer may be used to feed motor amps to the conveyor control system, commonly a PLC. The PLC may be programmed to accommodate different setpoints for different mechanical loads so that jam protection is provided from light to heavy loads. In situations where the conveyor is not able to accept analog signals NK Technologies has developed a patented transducer with a frequency output suitable for the Digital Inputs of most PLCs.
Fan Status: Independent Verification of Operation
Good engineering practice suggests that every control output should have a corresponding status input for verification. On fans and pumps a current operated switch can be snapped over one motor leg and the output fed to the automation system. NK Technologies’ self-powered Current Operated Switches will close when the motor turns on and open when the motor is off.
By adjusting the setpoint pump coupling or fan belt failure can be detected. This reliable solid-state solution eliminates the need for unreliable pressure current switches and their costly installation.