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Electric motors are found extensively in both the manufacturing and processing industries. Both AC and DC powered motors are used to drive pumps, fans, conveyors and a broad range of specialized equipment. There are many types of motors designed for many different applications, however all require electrical current in order to generate the magnetic fields that are necessary to create rotation. By measuring this current useful information can be made available regarding the status of the motor and the equipment that is connected to it. This may be as basic as independently verifying the run status of the motor or in conjunction with a PLC, for example, to protect a pump against dry run. Thus current may be used to both monitor and protect motors and motor-driven equipment.
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Pumps are similar to fans but they push or pull liquids or gases through a tightly confined space. Most are driven with electric motors, and monitoring the current or power used by the pump, a great deal of information about the system can be obtained. Bearings wear and cause the pump to consume more energy to operate. An open discharge line will create a condition where the drive motor uses less current than during normal operation, and if the pump is used to move waste water or sewage, the operator needs to know immediately that there is a problem. An impeller can become pitted from water bubbles or corrosion, and this can cause an over current condition. A power monitor measuring all three phases will detect a loss of phase before it can destroy the drive motor windings. All conditions will be detected well before a fuse opens, a circuit breaker trips, or the overload elements trip. |
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Electric heaters are used in a broad variety of industrial applications. Many chemical reactions require the addition of heat. Trace heating may be used to prevent process pipes from freezing or melt snow on roofs or car parks. Many plastic parts are manufactured using the addition of heat to mold them to the required form. The heat output of an electric heater is directly proportional to the square of the current flowing through it. Therefore measurement of current is useful for both process monitoring and heater status. If a heater fails, poor quality products or scrap material may be produced.
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NK Technologies manufactures current and power sensing products with ranges to 2000 amps directly, however, by adding a current transformer over the primary circuit, there is no limit to the range of alternating current that can be monitored. NK also manufactures current sensors which can be used to measure 1200 amps of direct current. Since the sensors are not in physical contact with the measured circuit, the primary voltage is limited only by the need for safety. |
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