Yokogawa WT332E 2-Element Digital Power Meter | 3-Phase AU

Two elements, one instrument, an efficiency number you can defend

Here’s a situation every drive and motor engineer recognises. You need the efficiency of a variable-speed drive: power in versus power out. So you set up two power meters, sync them as best you can, log both, export both, align the timestamps, and hope neither instrument drifted relative to the other during the run.

The Yokogawa WT332E digital power meter removes that whole exercise. Two independent input elements in one chassis, sharing one timebase, one A/D architecture and one calibration. Efficiency is computed inside the instrument. There is no timestamp alignment problem because there are no two timestamps.

That’s the practical case for a two-element meter, and it’s the reason the WT332E sits in so many drive-development and UPS-conformance benches.

What two elements actually buy you

The WT332E gives you two voltage inputs and two current inputs, and it supports two wiring configurations:

Three-phase three-wire (3P3W). This is the two-wattmeter method — the standard technique for measuring total three-phase power in a delta or three-wire star system without a neutral connection. Two elements are mathematically sufficient, and the WT332E does the summation for you: P∑ = P1 + P3, with apparent power derived as (2/√3)(S1 + S3) and reactive power as Q1 + Q3.

If your load is a three-phase motor, a delta-connected heater bank, an inverter output stage, or any three-wire distribution circuit, the WT332E measures it correctly with two elements. Adding a third element buys you nothing on a three-wire system.

Single-phase three-wire (1P3W). Two live conductors and a neutral. Common in split-phase supplies and in some industrial and transport applications.

Efficiency computation. This is the function that separates the WT332E and WT333E from the single-element WT310E — the two- and three-element models compute efficiency internally. Measure the input on element 1 and the output on element 3 and read the result directly.

Accuracy that holds up under scrutiny

Basic power accuracy is ±(0.1% of reading + 0.05% of range) at 45–66 Hz, and it holds across every measurement range rather than just a favoured one. That last point sounds like a footnote and isn’t — plenty of instruments quote a best-case range and quietly degrade elsewhere.

More importantly for motor and drive work: the influence at power factor zero is ±0.1% of apparent power between 45 and 66 Hz, half the figure of the previous generation.

Why that matters practically. A lightly loaded induction motor might run at power factor 0.3. At low PF, your total error is dominated by the low-power-factor influence term, not the reading error. Halve the influence term and you materially tighten the uncertainty on exactly the measurements that are hardest to make — no-load losses, standby losses, and the low-load end of an efficiency curve where the interesting differences live.

Voltage and current accuracy in the same 45–66 Hz band is ±(0.1% of reading + 0.05% of range). Yokogawa notes that the performance of the WT332E and WT333E matches that of the WT310E.

Bandwidth for inverter-driven loads

Modern three-phase loads are rarely fed a clean sine wave. A VSD output is a PWM waveform with high-frequency switching content riding on a variable fundamental. Measuring it with a meter designed around 50 Hz sinusoids produces confident, wrong numbers.

The WT332E covers DC and 0.1 Hz to 100 kHz, sampling voltage and current simultaneously at approximately 100 kS/s through a 16-bit A/D converter. Simultaneous conversion matters here: multiplexed instruments introduce a phase error between voltage and current channels, and phase error is precisely what corrupts a power measurement on a distorted waveform.

The auto data update rate function handles the other half of the problem. When a motor is spinning up or a drive is ramping, the input frequency is moving. Fixed update intervals either miss detail or fail to synchronise. Set the WT332E to AUTO and it detects the input cycle automatically, covering fundamentals down to 0.1 Hz.

Applications where the WT332E is the right call

Three-phase motor testing. Duration testing and efficiency measurement for industrial motors and rotating machinery. Integration runs to 10,000 hours — roughly a year of continuous logging. With the /C7 Ethernet option, Modbus/TCP lets Yokogawa’s GA10 data-gathering software combine your electrical data with temperature, torque and rotation speed from other instruments, up to 200 channels.

Variable-speed drive development. Input power, output power, efficiency, harmonic content and THD from one instrument. The /G5 harmonics option adds PLL-synchronised analysis to the 50th order with a settable maximum THD order.

UPS conformance and evaluation testing. The WT332E measures input and output levels, efficiency, frequency and THD for UPS performance testing — and the average active power function under integration mode gives a genuine consumption figure for loads that fluctuate rather than draw steadily. One instrument covers what would otherwise be a two-meter setup.

HVAC and refrigeration plant evaluation. Three-phase air conditioning, chillers and compressor packages evaluated for power draw and efficiency across duty cycles.

Distorted and special-waveform devices. Square waves, intermittent waveforms, chopped drives. The wide bandwidth and average active power measurement mean you don’t need special modes or workarounds to get an honest RMS and power figure.

Production line and QA on three-phase product. USB is standard; GP-IB (–C1) or RS-232 (–C2) is chosen at order; the /C7 Ethernet option adds Modbus/TCP and VXI-11 connectivity to Yokogawa recorders and FA-M3V PLCs. The /DA12 option provides twelve channels of ±5 V analogue output — three times the channel count of the single-element model, which is what you need when you’re logging two elements’ worth of parameters.

Australian context worth knowing

Australia’s standard three-phase supply is 400 V (nominally 415 V) between phases at 50 Hz. The WT332E’s 300 V and 600 V voltage ranges cover phase-to-phase measurement on that system directly.

Be clear on where it belongs, though. The WT332E is a measurement category CAT II, 600 Vrms instrument. CAT II covers equipment powered through a fixed installation and measurements made on that wiring. Yokogawa explicitly states it must not be used for CAT III or CAT IV measurements — that rules out distribution boards, circuit breakers, sub-mains and service entrance work. This is a bench, test-rig and machine-terminal instrument, not a switchboard instrument. If your work is on the switchboard side, you need a differently rated tool.

Order the –R power cord suffix for the AS-standard plug. Supply is 100–240 VAC at 48–63 Hz, 70 VA maximum, so it runs on Australian mains without an adapter.

One more note that matters on site: this is a Class A industrial instrument under EN 55011. Operating it in a residential environment may cause radio interference, and correcting that interference is the user’s responsibility.

Why buy the WT332E from us

Two-element versus three-element is the single most common ordering mistake on this product family, and it isn’t always obvious which one you need. The short version: if your system has no neutral connection carrying current, two elements is the correct and complete answer. If it does, you need three.

We’ll work through your wiring configuration with you before you order — along with the option codes, because /G5, /C7, /EX1, /EX2 and /DA12 are all factory-fitted selections that can’t be retrofitted casually.

We supply, we support, and we handle calibration. Get in touch with your application and we’ll help you spec it properly the first time.

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TECHNICAL SPECIFICATIONS

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What is the Yokogawa WT332E used for? The Yokogawa WT332E is a two-element digital power meter used to measure three-phase three-wire (3P3W) and single-phase three-wire (1P3W) power. Its two input elements allow input and output power to be measured simultaneously on one instrument, so efficiency is computed internally — making it well suited to variable-speed drive development, three-phase motor testing, UPS conformance work and HVAC plant evaluation.

How many elements do I need for three-phase measurement? It depends on the wiring, not the phase count. A three-phase three-wire system (delta, or star without a current-carrying neutral) requires two elements — the two-wattmeter method is mathematically complete, so the WT332E is the correct choice. A three-phase four-wire system with a neutral requires three elements, which means the WT333E. Choosing two elements for a four-wire system will produce incorrect total power on any unbalanced load.

Can the WT332E calculate efficiency? Yes. Efficiency computation is built into the WT332E and WT333E (it is not available on the single-element WT310E). Measure input power on one element and output power on the other, and the instrument computes efficiency directly — with both measurements sharing the same timebase and the same calibration, which eliminates the drift and synchronisation errors inherent in a two-meter setup.

What is the difference between the WT332E and the WT333E? The WT332E has two input elements and supports 1P3W and 3P3W wiring. The WT333E has three input elements and adds three-phase four-wire (3P4W) and three-voltage three-current (3V3A) configurations. Electrical specifications, accuracy, bandwidth and current ranges are otherwise identical. Choose the WT332E for three-wire systems and efficiency measurement between two circuits; choose the WT333E if you need four-wire measurement or phase-by-phase data on all three phases.

Can the WT332E measure the output of a variable-speed drive? Yes. Bandwidth of DC and 0.1 Hz to 100 kHz covers PWM switching content, and voltage and current are converted simultaneously at approximately 100 kS/s so no phase error is introduced between channels — which is what preserves power accuracy on a distorted waveform. The auto data update rate function tracks a changing fundamental frequency during ramps down to 0.1 Hz.

Is the WT332E suitable for measuring 415 V three-phase in Australia? The 600 V voltage range covers 400/415 V phase-to-phase measurement directly, and the instrument runs on Australian 230 V, 50 Hz mains. However, it is a measurement category CAT II, 600 Vrms instrument, which Yokogawa states must not be used for CAT III or CAT IV measurements. That means it is appropriate at machine terminals and on test rigs fed from a fixed installation, but not for distribution board, sub-main or service entrance measurement.

How long can the WT332E log for? Integration runs for up to 10,000 hours — approximately one year. Auto ranging remains available during integration for ±Wh, Ah and DC current, so a load step partway through a long run doesn’t invalidate the result. With the /C7 Ethernet option, Modbus/TCP allows continuous data capture into Yokogawa GA10 software alongside temperature, torque and speed data on up to 200 channels.