Isolated Alarm System Interfacing
If an alarm or monitoring system is to be installed adjacent to another, (for example: 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.
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.
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.
Moisture Ingress on a Submersible Pump Motor
An NK Technologies’ Ground Fault Sensor installed on a submersible pump motor provides an easy to install replacement or addition to moisture sensors housed in the motor casing. Unlike moisture sensors that have to be wired back to the motor control center, the GF sensor is installed in the motor control center. By detecting the ground fault current resulting from moisture ingress or other potentially dangerous condition remedial action can be taken prior to catastrophic failure. Either the pump can be replaced at the next convenient time or switched off and a back-up pump started.
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
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.
DC Motor Installations
Many applications requiring high torque at low speeds, like bridge cranes and log carriages, use DC shunt wound motors. Since it is relatively easy to control the speed of a DC motor by adjusting the voltage to the field windings, precise regulation is afforded to applications like printing press paper feeds or web control of multiple motors in the paper making process. Using an NK Technologies’ DC Current Transducer will provide an analog signal that can be used to keep the motor from over-current situations. Using an NK Technologies’ DC Current Operated Switch will insure that if the motor field supply is lost, the motor will not over-speed to the point of self-destruction.