Motor Monitoring 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 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 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 system, 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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The performance of size reduction equipment like crushers or grinders can be optimized by controlling the in-feed in order to Help prevent jamming Improve the uniformity of the resultant product Enhance overall production efficiency

By installing an NK Technologies' Current Transducer or Power Transducer to monitor the infeed to a crushing process, the speed of the in feed drive can be slowed when the crushing motor is working too hard, or the speed can be increased when the crusher is under worked. The analog 4-20 mA proportional signal is fed directly into a VFD, and the drive does the rest of the control.

Additionally, NK Technologies' Current Operated Switches installed on other conveying motors can be used to signal malfunction (for example over-load or motor failure) to help prevent cost equipment damage.

NK technologies current sensors come in a variety of configurations for quick and simple installation either for the OEM or End-User.

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Often a band saw is used to cut logs into rough planks, before the planks are processed into finished lumber. Due to inconsistencies in the log (knots, burls and checks), the speed that the log is pulled through the saw must be varied. The operator will often reduce the speed of the cut when smoking occurs, or the blade breaks. By installing an NK Technologies' Current Transducer the operator's job is made easier. By watching the log and a display representing the current draw of the band saw, the operator can achieve a higher rate of output with less down-time. A similar arrangement can be used with circular saws. The blades become brittle after excessive heating if they are worked too hard. Many automatic systems are in use whereby the currert draw is used to reduce the motor load typicalIy by reducing the feed-rate.

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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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Spin Pumps are used in the manufacture of synthetic fibers and yarns. Very precise control is required to insure that the product feed rate and the fiber draw rate are matched. It is critical to monitor and protect these spin pumps because they are the heart of the system and are required to run continously. By installing an NK Technologies' Current Transducers, the motor current may be monitored providing the control system with key information regarding load. Various in load may be attributable to a number of factors such as bearing failure, seal failure, suction loss etc. The measurement of load together with other process variables like pressure and flow can provide invaluable information regarding the operation of the vital spin 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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