Precisely measure power in three-phase and multi-phase systems

Modern power electronics rely more and more on multi-phase systems. While such configurations improve performance, the higher number of phases complicates measurement and evaluation and can cause production and testing bottlenecks.

LMG600 Series Power analyzer
LMG600 Series Power analyzer

Your task

DUT connections to measuring devices are complicated and varied. One specific challenge is characterizing systems without neutral connections (common in motor testing) or where neutral measurement points are unavailable. Reliable multi-phase power analysis is very difficult without a neutral point.

Rohde & Schwarz solution

ZES ZIMMER LMG600 power analyzers can accurately and quickly analyze complex multi-phase systems. The L6-OPT-SDC star-delta conversion option can help characterize systems without a neutral connection and built-in standard wiring settings (two-wattmeter, star and direct connection) eliminate manual configuration to reduce development times.

In addition to versatile wiring, ZES ZIMMER LMG600 power analyzers eliminate measurement errors with advanced synchronization. By minimizing circuit time delays to less than 4 ns and compensating for physical channel positioning, the system has absolute timing precision across all phases.

To further simplify complex workflows, ZES ZIMMER LMG600 power analyzers have flexible channel groupings. Users can dynamically group channels for uniform settings and customized naming that adapts the hardware seamlessly to the application and reduces validation times.

Regardless of setup complexity or hardware constraints, ZES ZIMMER LMG600 power analyzers offer a customized, high-precision measurement solution tailored to your specific accuracy needs.

Fig. 1: Different connection diagrams
Fig. 1: Different connection diagrams
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Many measurement setups for three-phase systems

The delta connection is designed for systems with three wires and no neutral measurement point (three-phase motors, traction inverters, industrial ovens and HVAC transmission lines). The method enables total three-phase power coverage. Star-delta conversion is vital for calculating power per phase. The ZES ZIMMER LMG600 series has a high common mode rejection ratio (CMRR) at the input to ensure precise measurements at balanced highpower loads.

A direct connection or a star configuration measures phase voltage relative to neutral or ground in a four-wire system. Unlike a direct connection, star configurations

include a mathematical conversion of the system. Both methods are important when characterizing power distribution infrastructure and transformers. The direct connection is scalable and variants of it can be applied to six, nine and twelve phase systems for consistent monitoring across high-power applications.

The two-wattmeter method (Aron circuit) can also optimize active power measurement for symmetrical three-phase systems with a 120° phase shift. Transforming two measurements into three-phase voltage provides an efficient solution when power channels are limited or high-precision analysis is not required (see Fig. 1):

Advanced software for multi-phase analysis

The LMG600 series software is engineered to eliminate timing errors in complex multi-phase measurements. By synchronizing measurement paths and channels, the system ensures all collected data corresponds to the exact same moment in time, preventing physical delays from compromising measurement precision.

To ensure accuracy, the system specifically targets phase angle and power factor errors. Since voltage and current paths often have different circuit time delays, the LMG600

series reduces this difference to less than 4 ns. The synchronization eliminates the risk of skewed results from varying internal path lengths.

The software also automatically compensates for delays caused by the physical positioning of the power channels. Accounting for such hardware-level timing differences improves system precision across all active channels.

The software also simplifies the three-wire measurement method. Integrated mathematical transformations, such as the star-delta conversion, transforms different wiring configurations into equivalent circuits and maintains consistent results for power quality analysis.

Flexible channel grouping for multi-phase applications

The LMG600 series allows dynamic grouping of consecutive channels of the same type for consistent configuration across the system. Grouping channels helps uniformly apply specifications such as filters, harmonics computation settings and synchronization sources and eliminates the need for repetitive manual setups.

Each group can be configured in detail to meet specific project requirements and optimize workflows. Rapid adjustments can be flexibly made to channel arrangements, letting the hardware adapt to an application rather than constraining it.

Groups can also be given customized names to improve organizational clarity, reduce configuration errors and makes it easier to manage complex multi-phase setups.

Applications

Accurate results depend on the alignment of software settings and physical wiring. Follow the LMG600 setup examples for guidance.

Three-channel measurements

Star wiring

When the system neutral wire is accessible, star wiring is recommended.

1. Wire your system as shown in Fig. 3
2. Go to Group Setup
3. Choose Grouping
4. Click on the Grouping button to enter Grouping Editor
5. Merge the three channels corresponding to the physically connected channels by clicking on one horizontal arrow twice
6. Name the group after your power conversion step by clicking over the default name
7. Go to the respective group tab
8. Choose “U⅄I⅄“ by long pressing over wiring

Three-channel measurements
Fig. 2: Group settings configuration when using star wiring | Fig. 3: Practical star wiring of three channels at LMG600
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Direct wiring

If no conversion is required, choose direct wiring.

1. Wire your system as shown in Fig. 5
2. Go to Group Setup
3. Choose Grouping
4. Click on the Grouping button to enter Grouping Editor
5. Merge the three channels corresponding to the physically connected channels by clicking on one horizontal arrow twice
6. Name the group after your power conversion step by clicking over the default name
7. Go to the respective group tab
8. Choose “Direct” by long pressing over the wiring

Three-channel measurements
Fig. 4: Group settings configuration when using direct wiring | Fig. 5: Practical direct wiring of three channels at LMG600
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Delta wiring

If no neutral connection is available, delta wiring is often the best option.

1. Wire your system as shown in Fig. 7
2. Go to Group Setup
3. Choose Grouping
4. Click on the Grouping button to enter Grouping Editor
5. Merge the three channels corresponding to the physically connected channels by clicking on one horizontal arrow twice
6. Name the group after your power conversion step by clicking over the default name

Three-channel measurements
Fig. 6: Group settings configuration when using delta wiring | Fig 7: Practical delta wiring of three channels at LMG600
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Two-channel measurements

Two-wattmeter method

If minimizing channel usage is more important than high precision, the two-wattmeter (Aron) method is advantageous.

1. Wire your system as shown in Fig. 9
2. Go to Group Setup
3. Choose Grouping
4. Click on the Grouping button to enter Grouping Editor
5. Merge the two channels corresponding to the physically connected channels by clicking on one horizontal arrow once
6. Name the group after your power conversion step by clicking over the default name
7. Go to the respective group tab
8. Choose “Aron” by long pressing over wiring

Two-channel measurements
Fig. 8: Group settings configuration when using two-wattmeter (Aron) wiring | Fig. 9: Practical Aron wiring of two channels at LMG600
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Overview of wiring examples

Grouping set Wiring available Conversion required?
1-channel direct connection no
2-channel direct connection,
Aron circuit
no, for direct or pure total
power
3-channel direct connection,
U⅄I⅄, UΔI⅄
yes, for transformation and
individual phase readings

Summary

Testing complex multi-phase systems requires absolute timing precision and flexible hardware configurations for measurement validity. The LMG600 series provides advanced and high-precision solutions that accelerate the analysis of multi-phase architecture with integrated wiring methods and advanced synchronization software, reducing development time and ensuring valid, skew free results.

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