Equipment such as turbines, high speed compressors with associated gearboxes and large generators are susceptible, over time, to producing shaft voltages which result in stray currents. These currents can increase to become highly destructive and may do so without forewarning. The only effective protection for critical applications is afforded by continuous monitoring. Less critical installations may benefit from periodic measurements. Several versions of shaft voltage and current measuring and monitoring devices are available to suit requirements. Many different types of faults may be detected by shaft condition monitoring.
The most basic is the SCMeter which is intended for periodic inspection and measurement of either grounding current or shaft voltage. The SCMeter measures Peaks and Averages of either the Current or the Voltage and it provides an easy-to-access interface for periodically measuring the electrical grounding current and shaft voltage profiles in rotating machinery.
The VCM-C Voltage Current Monitor is an on-line monitor which is used in conjunction with any insulated shaft grounding brush and voltage measuring brush. It measures peak and average currents, and peak voltage. The model VCM-C is battery operated and push button to read. It has no alarm or analogue outputs.
The VCM-E Voltage Current Monitor is a continuous on-line monitor which is used in conjunction with any types of insulated shaft grounding and voltage measuring brushes. It measures peak and average currents, and peak voltage. The model VCM-E is designed to be powered from a permanent AC supply and is provided with continuous 4-20 mA outputs and alarms for brush performance failure or high voltage. It is intended for connection into a plant SCADA system so that shaft electrical condition signals can be trended. See specification for details.
The VCM-E is available in Non-explosion-proof and Explosion-proof enclosures.
A dual VCM-E option is also available for large, redundant or custom applications.