With ever increasing demands for electrical power the power generating companies 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.
KB Category Archives: Aggregates/Cement
Installing an NK Technologies’ Current Transducer over the conductors on the secondary 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.
The need for back-up power for critical loads is becoming more and more apparent 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.
C.T.s (Current Transformers) have been used for many years to measure AC amperage. 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.
The detection of a single phase heater failure by measuring the temperature is like measuring the effect rather than the cause. By installing an NK Technologies’ Current Operated Switch heater failure can be detected before cooling has had time to occur. The signal from the current sensor can be used to switch on a back-up heater, stop the equipment, alarm the equipment operator or trigger the appropriate action.
For 3-phase heaters installing an NK Technologies’ Current Transducer on each leg of a delta connected heating array is the best way to detect loss of one element. Unlike a typical induction motor, there will not be a substantial change in the current draw of the two adjacent phases when a heating element open circuits. The load has disappeared, and the work of heating will not be shared by the other elements. There will be a reduction in thermal output, which can take quite some time to detect with temperature sensors like thermocouples. A current transducer will identify the problem in milliseconds! Poor product quality can be prevented and large quantities of raw material can be saved by quick action.
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.
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.
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
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 overload (pump jam), underload (suction loss) or underload & overload can be detected quickly before damage occurs.
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.