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Monitoring the Electric Motor in Pumps Can Help Prevent Pump Failure

With one of the broadest product portfolios in the industry, NK Technologies provides reliable, innovative current sensing products designed to add value and exceed our customers' expectations. From motor monitoring to heater status, semiconductor tools to water/wastewater plants, NK Technologies has a family of current sensors to meet your application needs.

The majority of pumps use electric motors as the prime driving force. Monitoring the properties of the electrical power supply provides valuable data that can be used to prevent failure of the pump as the equipment wears from use or environmental exposure. It is important to monitor the following:

Pump & Motor

  • Monitor Current Draw:

    Place a a current sensing relay or switch over a lead powering the pump driver and set it so a contact closes or opens when the current draw of the pump exceeds a limit. The contact can trigger an alarm, or open the contactor operating coil in an over-current condition caused by a jammed impeller, failing bearings, or corrosion of any rotating component. Conversely, a current sensing relay or switch can sense an abnormal reduction in current caused by an open discharge, broken coupling between motor and pump, or a blocked intake line.

  • Monitor Change in Current Over Time:

    Use an analog output sensor with a constant signal proportional to the primary current to monitor the change in current over time. As the pump system wears, current use will increase indicating a problem. Maintenance can be performed before the problem becomes catastrophic.

Motor Drive Sensor

  • Monitor Phase Loss:

    Use a voltage monitor to detect phase loss, whether it is at the motor terminals or at the source. Starting a three-phase motor in a single-phase condition will likely damage the motor windings quickly, resulting in a rewind or replacement.

  • Monitor Power or Wattage:

    Most motors draw at least 50% of the nameplate full load current in an "open-shaft" or free spinning condition. Add the torque required to turn the pump mechanically and the pump will be draw over 50% of nameplate current, increasing in a very linear manner proportional to the load. If it is a critical load, or uses an over-sized motor for the load, use a power monitoring device to monitor power or wattage. Since watts are calculated by measuring the voltage, current and power factor, the transducer output will always be directly proportional to the load.

  • Monitor for Earth Leakage:

    Monitor earth leakage with a ground fault sensor to prevent damage to equipment or injury to personnel from phase to earth faults. The output contact can be selected to close, operating a shunt trip circuit breaker, or a contact can open the circuit to a contactor coil. Both would shut down the monitored load so maintenance can be performed.

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NK Technologies Transducers

The Large, Easy-to-Install Solid-Core Design allows for quick installation even in applications where there are multiple conductors per phase. Just thread the conductor through the extra large aperture and reconnect on the other side. The transducer output is powered from excitation voltage of around 24 VDC, using just two wires. The sensor mounts on a back panel or a DIN rail, and is designed to accommodate wire sizes for loads up to 400 A.

Vacon Drives

Compared to Conventional Control Schemes, VACON AC Drives are typically able to reduce energy costs by as much as 30% in pump and fan applications, usually offering a return on investment of less than a year. Pumps and fans control the flow of water and air through the pipes, vents and waterways that are often out of sight, and yet remain central to our lives. Like in so many industrial processes, AC drives optimize these systems and make sure that