Water / Wastewater Applications

Pumps can become jammed due to foreign matter and cause damage to both the pump and the motor before thermal overloads are tripped. Additionally a blockage in the suction line of the pump can cause the pump to run dry, overheat and break a seal.

By simply installing an NK Technologies' self-powered Current Operated Switch in one leg of the motor overloads (pump jam), underload (suction loss) or overload can be detected quickly before damage occurs.

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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 legs 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 switches and their costly installation.

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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 can be used to monitor conveyor motor amp draw and output this data to the conveyor control systems, commonly a PLC. The PLC may be programmed to accomodate 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

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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.

See also: Pump Jam & Suction Loss Protection & Moisture Ingress on a Sumersible Pump Motor

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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 catastrophe failure. Either the pump can be replaced at the next convenient time or switched off and a back-up pump started.

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Many applications requiring high torque at low speeds, like bridge cranes and log carriages, use DC shunt would 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.

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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.

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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.

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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 (ATR Series) 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 (ATR Series) 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 (APS Series) 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 (AS1/AS3 Series) are used to coordinate operations between conveyor, washing and drying systems.

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High technology lamps have been developed for a variety of specialized industrial and commercial applications. These lamps are expensive and their useful life should be maximized. Installing an NK Technologies' Current Transducer to measure the current draw of a lamp provides the information to determine the lamp's condition by comparison to known characteristics. Intelligent control devices, like PLCs, are programmed to adjust the applied voltage or current to optimize the life of the lamp.

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Ultraviolet (UV) lamps are used commonly to disinfect water by killing bacteria. High Intensity Infra Red (IR) lamps are used in a variety of industrial processes to provide heat both for drying and curing processes. Correct operation is very important and can be determined by measuring current draw. Using an NK Technologies' Current Operated Switch (AS1/3 series) provides simple and quick verification. The on/off contacts of the switch may be used to simply indicate status to an operator using a lamp or wired to the input of a PLC preprogrammed with the necessary corrective action. Alternatively, N K's Current Transducers (AT Series) may be used to provide an accurate measurement of the current draw by a UV, IR or other light source.

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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.

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Industrial re-chargeable battery systems are used to provide primary power for vehicles and back-up systems for critical equipment, like cell phone base stations and other communication 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 Transducers. 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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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.

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