Drives and Controls Magazine
Dual-role instrument can test motors and drives
Published:  24 January, 2014

New ways of testing motors and drives could emerge following the launch of an instrument that combines power analysis with oscilloscope-style time-based measurement. Its developer, Yokogawa, describes the PX8000 as “the world’s first precision power scope”.

According to Terry Marrinan, vice-president of Yokogawa Test & Measurement for Europe and Africa, the new instrument means that users “need no longer compromise on high-accuracy time-based power measurement: a need that conventional power analysers and oscilloscopes were never designed to meet”.

The instrument’s 12-bit resolution, 100 MS/s sampling and 20MHz bandwidth mean that it can be used to measure inverter pulse shapes accurately, and thus to fine-tune inverter efficiencies. Its X/Y display capabilities can be used to show the speed/torque characteristics of motors.

The device can also be use to measure and analyse transient power profiles. It allows simultaneous voltage and current multiplication to give real-time power sampling, supporting both transient measurements and averages across a sample period. Up to 16 different waveforms – including voltage, current and power – can be displayed side-by-side.

The PX8000 can measure the harmonic components of voltage and current waveforms, as well as harmonic distortion factors, simultaneously. Harmonic measurements – up to the 500th – can take place in parallel with conventional voltage and current measurements.

To evaluate three-phase electrical systems, at least three power measurement inputs are required. The PX8000 has four and can capture and display voltage and current simultaneously across all three phases.

There is a choice of plug-in input modules covering voltage, current and sensor measurements up to 1kV rms and 5A rms (or higher with external current sensors), with a basic accuracy down to ±0.1%.

Yokogawa's PX8000 instrument combines power measurement and oscilloscope functions

The instrument also supports the capture of power waveforms over specific periods through the definition of start and stop “cursors”. This is useful for examining transient phenomena.

A memory function automatically records up to 1000 historical waveforms, which can be recalled and redisplayed at any time. An automatic de-skewing function eliminates offsets between current and voltage signals that may be caused by sensor or input characteristics.

Yokogawa says that typical applications for the PX8000 will include inverter and motor testing, reactor loss measurements for inverter boost circuits, and assessing transient responses of industrial robots.

Prices in Europe start at around €12,000.