Feeling like your electrical efficiency is sub-par? Submetering might be exactly what you need to optimize your building – and your business.
Practical tips for monitoring and regulating power consumption
Large, 3-Phase motors, compressors, pumps, and equipment used in an industrial setting benefit from operating at certain voltages (and amperages). While managers and machine operators may be aware of the OEM specs and operational guidelines, few practice practical condition and energy monitoring over the lifetime of their equipment. By tracking equipment performance and detecting fluctuations early on, you can easily – and significantly – extend the lifetime value of your most expensive equipment.
From electricians to homeowners, city planners to CEOs, energy monitoring is a buzzword that means more than environmental friendliness, it means big savings.
Topics: Energy Savings
When it comes to measuring alternating current (AC), few devices offer the user-friendliness and accuracy of Rogowski coils. These rope-style current transformers (CTs) are able to encircle a live conductor, such as a current-carrying cable, without disturbing it and determine the output current. Also known as flexible core coils, Rogowski coils offer a number of unique benefits and possible applications.
This paper describes how to transform interval data to actionable information to identify low cost control changes, demand control opportunities, and rate analysis. The primary means of collecting interval data is the low cost pairing of Magnelab current transformers (CTs) with a subscription-free eGauge monitor. Case study examples are provided from projects in Colorado.
Why do you care about burden when ordering current transformers?
Many of our customers regularly request quotes for standard and custom 5A ratio type current transformers but only ask for the window size and the input current with no knowledge of the "burden". The burden is specified as VA or resistance (or impedance). We can not guarantee the accuracy without the burden.
The burden is the termination impedance of the measuring instrument. The measuring instrument can be an analog or digital energy meter, a data logger or a recorder. All instruments that use a current transformer to measure line current must terminate the CT with a resistance (impedance in same case which means there is some inductance involved).
Many meter manufacturers and others ask why use a Magnelab standard, pre-burdened voltage output current transformer (CT) for monitoring power instead of the traditional 5 amp output current transformer (CT) that’s been used for decades. There are several similarities and differences between the two CT types--the similarities are that both CT’s operate under the same principles of magnetic theory, they both provide isolation between the primary and secondary conductors, and both generally use a single turn primary winding. Because the differences are more complex, I’ll expand on the characteristics of each.
A question is often asked about what the difference is between the tolerances specified by Magnelab and other companies. Don’t be deceived by the numbers or catch phases, know what you are getting when ordering current transformers (CT’s). When looking at the specifications for a CT, the accuracy rating or class can be depicted in many ways. In order to insure the correct CT is chosen for a given application it’s important to know what the specifications are stating, or not stating. Below are examples of tolerances and ratings you may see where “X” represents the accuracy:
Magnelab has recognized that in most applications requiring an accurate measurement of the amount of current passing through a conductor, current to current transformer outputs must be converted, or burdened, into a usable and measurable voltage output. It has also been determined that if this is not done correctly, the phase angle shift and output voltage amplitude and linearity cannot be accurately controlled.
Magnelab has developed two U.L. listed current transformer styles that are designed to eliminate this problem. The SCT series are split core (opening) style current transformers, and the UCT series are solid core style current transformers. Both are manufactured and pre-burdened to a specified output voltage in a controlled environment in order to ensure the minimum phase angle shift, primary to secondary, and maximum voltage output accuracy and linearity over the specified primary current range.
The basic theory of a flexible Rogowski coil was first postulated in 1912 by the German physicist Walter Rogowski. A flexible Rogowski coil is an air core toroidal transformer which has been a very useful and innovative tool in the transformer industry due to its ease of use and primarily due to its lack of saturation at high currents.
Major advantages of the Rogowski coil:
- Measurement of a wide range of amperages without saturation
- Detection of small AC changes in the presence of large DC loads
- Wide range of frequencies from Hz to MHz
- Flexible installation without power interrupt
- No additional power burden to the primary conductor being measured