LeCroy announces software to analyze control and drive of three-phase motor with oscilloscope

Teledyne LeCroy Japan announced on October 1st the software “Motor Drive Power Analysis Software” for analyzing the control and drive of three-phase motors with an oscilloscope. It will be sold as an option for the 8-channel input oscilloscope “HDO8000 series” announced by the company on June 18. The beta version will be available in October and the official version will be available in January 2015. The planned sales price is 700,000 yen (excluding tax).

Oscilloscopes (digital oscilloscopes) typically have a vertical resolution of 8 bits and an analog input channel of up to 4 channels. Since most oscilloscope applications are small signal measurements, it is basically unthinkable that this specification will be insufficient. However, 8-bit resolution may not be sufficient for power measurement that handles high voltage and high current. For example, when dealing with a high voltage such as 600V, it is difficult to accurately observe the difference of 5V with a resolution of 8 bits (256 divisions). In addition, recent motors for home appliances and motors for electric vehicles (including hybrid vehicles) are often controlled by three-phase AC signals. The measurement of motor control signals requires two channels of analog input with current and voltage per phase. A motor driven by three-phase alternating current (three-phase motor) requires at least six analog input channels. With a normal 4-channel input oscilloscope, one is not enough. You must have at least two 4-channel input oscilloscopes.

The “HDO8000 series” is an oscilloscope developed for such applications. Since the vertical resolution is 12 bits (4096 divisions), the signal can be observed with a resolution of less than 1V even at full scale 600V. And since it has as many analog input channels as 8 channels, even if 6 channels are assigned to the measurement of 3-phase motor control, there is still room for 2 channels.

Overview of oscilloscope “HDO8000 series”

Debug the control software of the microcomputer

Inverter-based motor drive circuit and its measurement

Measure the behavior of the motor (torque, rotation speed, etc.)

Motor drive circuit by inverter control using a microcomputer and its analysis (overall image)

However, the analysis of the three-phase motor control circuit is not so easy. Three types of measurement: debugging control software by observing the PWM (Pulse Width Modulation) output and serial data output of the microcomputer, measuring the inverter type motor drive circuit, and measuring the behavior of the motor (torque, rotation speed, etc.) An analysis needs to be performed. In order for an engineer to build such a measurement environment with only simple hardware such as an oscilloscope, it requires extremely advanced technology and a large workload. By incorporating the optional “motor drive power analysis software”, the burden of such analysis work is greatly reduced.

Analysis using a combination of the oscilloscope “HDO8000 series” and “motor drive power analysis software”.Since the maximum clock frequency of the microcomputer was assumed to be 400MHz, the maximum input frequency of the HDO8000 series was decided to be 1GHz.

In the past, measurement of motor control circuits was often performed by adding a motor evaluation option to the power analyzer. However, Teledyne LeCroy Japan argues that the power analyzer has a limited waveform observation function compared to the oscilloscope and is not suitable for debugging microcomputer control software. On the other hand, the power analyzer is superior in the measurement accuracy of motor control signals (voltage and current), and if you want high-precision measurement results, you should use the power analyzer.