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The Basics of Power Analysis in OXYGEN


Power analysis is a very extensive topic. You have to be familiar with different parameters and calculation algorithms before setting up a power analysis on your own. Our measurement software OXYGEN offers you a comprehensive power analysis feature that is worth to explore. But before you start, it is helpful to know some power analysis basics and how they work in OXYGEN.

This blogpost gives you an introduction in using the OXYGEN power analysis feature.

Connection of three-phase power system

Three-phase power systems are the most used method for generating, transmitting and distributing power. For more details about three-phase power engines, we also prepared a blogpost with in-depth explanations of this topic.

To start with power analysis in OXYGEN, you need to physically connect those three phases to a DEWETRON Power Analyzer.

DELTA or STAR configuration

To connect the three phases to your Power Analyzer in OXYGEN, you can use a DELTA or STAR configuration. When you use a DELTA configuration, you measure the line-line voltages. This means to measure between phases. With our Power Analyzer, you have the possibility to measure current directly by using current inputs. Most applications need a current transducer because of high currents. You can also use shunts or transducers to measure current indirectly. You also have to measure voltage and current for the inverter.
The left picture in Figure 1 shows how the DELTA configuration works with the TRION-1820 power modules.

Another way of setting up your power analysis is the STAR configuration. Compared to the DELTA configuration, it has an additional wire – the neutral line. Within the STAR configuration, you measure the phase-line voltages. It contains a virtual star point that should also be connected with the neutral line of the motor. If the neutral line is not accessible within the STAR configuration, the virtual star point could float. In this case, we recommend to use the DELTA configuration because it only contains three wires and three phases.
The right picture in Figure 1 shows how the STAR configuration is connected.


Figure 1

As it is not possible to use the STAR configuration in our case, we proceed with the DELTA configuration. The type of configuration you choose should not influence the measurement results. When you use the DELTA configuration, our measurement software will recalculate the phase-to-phase voltages and you can see the STAR voltages as well.

How to use a current transducer

Although it is possible to measure current directly with our Power Analyzer, in most cases it is necessary to use current transducers to measure multiple hundreds of amps.

To measure high current values, you have to scale the current transducer in OXYGEN. Depending if the current transducer has a voltage or current output, different measurement modules can be used. For a current transducer (e.g. LEM IN 500) you need to know the number of secondary turns to configure it in OXYGEN. You can find the value in the datasheet. Open the setup of the module the current transducer is connected to. Then enter the number of secondary turns in the field Scaling. That’s the whole configuration work you have to do prior to using a current transducer in OXYGEN.

If you have different current transducers or use your current transducer for every measurement task, you can also set it up as a sensor in the sensor database. There you can store sensors and their configuration for use whenever needed. This saves valuable time during the system configuration.

The sensor database is saved as XML file and can also be used on another DEWETRON measurement device or PC. Read our blogpost “10 questions about OXYGEN” to learn more about the sensor database and how it works!

Power groups in OXYGEN

A power group in OXYGEN is like a calculation group where the power parameters are calculated for the selected voltage and current channels. You can freely define the channels you would like to use for calculation. For example, a motor could be a power group. Learn more about power groups in OXYGEN and how they work.

In our past webinar, Verena and Ivica demonstrated different methods to create a power group in OXYGEN. Watch the webinar video and learn how it works!

Do you also want to learn how to calculate the efficiency of an inverter, how long-time measurements work and how the calculation intervals are defined in OXYGEN? Then you should also watch the video of our past webinar and you will learn how those, and more measurement tasks can easily be set up in OXYGEN!

If you already have some experience with the topic of power analysis, then we recommend to participate in the webinar “The Capabilities of OXYGEN’s Power Advanced Feature”. Check out the upcoming dates and register now!
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