Instrumentation for Resolver Design in Electric Personal Mobility Devices (PMD)s

Introduction

It is estimated that approximately half of the world’s electric energy is consumed by motors. With the increasing adoption of electric vehicles (EVs) and robots, demand for motors is expected to grow, making energy efficiency more critical than ever. As operating conditions for motors in EVs and robots can vary, there is a rising need for precise measurement not only of steady-state power consumption but also of instantaneous power during transient events, such as rise times.
Inverters, widely used in motor control systems, contribute to energy savings by rapidly switching multiple devices on and off through advanced control schemes. During the design phase, it is essential to perform detailed waveform measurements to verify key parameters such as voltage levels (including surge voltages) and signal timing margins.
Inverter evaluation often requires repeated testing across multiple measurement points. Instruments with only a few channels can limit visibility into the operation of other components during critical events, making comprehensive analysis challenging. To fully assess inverter performance and ensure optimal operation, measurement tools must capture the interactions between various devices under different conditions.

Challenges

A typical inverter consists of six switching devices, meaning that four-channel oscilloscopes are insufficient for simultaneous observation and analysis of all device operations.
Additionally, inverter evaluation requires an oscilloscope with long memory to capture entire waveforms while still allowing for detailed analysis of specific segments.
To optimize inverter performance, it is essential to monitor various signals—such as gate drive signals—from multiple perspectives. During the design and troubleshooting phases, precise measurement of voltage and current at key points, including rectifiers, power factor correction (PFC) circuits, and switching stages, is crucial for ensuring proper functionality and improving efficiency.

Solutions by the DLM5000

• Eight analog channels, expandable to 16 channels by linking two units.
• 12-bit High Resolution
• Deep Memory Supporting Up to 1 GPoints of Data Capture
  *1 Gpts is an optional feature for the DLM5000HD
• History Function
• Dual zoom windows enabling simultaneous viewing of different waveform sections.
• Switching Loss Analysis
• Power Analysis

Figure 1. Example of inverter measurement

Explanations of Solutions with the DLM5000

Eight analog channels, expandable to 16 channels by linking two units

Using two DLM5000HD or two DLM5000 units (with the synchronization option) connected via the dedicated cable allows synchronized measurement of up to 16 analog channels and 64-bit logic inputs. A built-in interface supports this functionality, with the option to activate it later using an additional feature license.
Waveforms are displayed on their respective units, with synchronized triggers, record length, sample rate, acquisition settings, and horizontal scale, enabling the system to operate as a unified 16-channel oscilloscope.
* The DLM5000 and the DLM5000HD cannot be connected through the DLMsync function.

Figure 2. Connecting two units using a dedicated cable

The two synchronized instruments are linked, with operations shared between the main and subunits. For example, when one unit displays a zoomed-in waveform, the other automatically zooms to the same section. Measurement data can be output collectively, and when used with the IS8000 Integrated Software Platform, all 16 channels can be monitored simultaneously.

Figure 3. IS8000 Integrated Software Platform

12-bit High Resolution

The 12-bit measurement capability of the DLM5000HD is especially effective for accurately capturing details like ringing after overshoot. With optimal range settings, it can detect subtle waveform changes while maintaining a comprehensive view of the entire signal.

Deep Memory Supporting Up to 1 GPoints of Data Capture

The DLM3000 and DLM5000 can capture waveforms of up to 0.2 seconds at a 2.5 GS/s sample rate and up to 10 seconds at 50 MS/s. The DLM3000HD and DLM5000HD extends this capability, capturing waveforms up to 20 seconds at 50 MS/s.

History Function

The DLM5000 automatically stores up to 100,000 captured waveforms in acquisition memory (up to 200,000 with the DLM5000HD), all of which can be easily retrieved for later analysis. Users can choose to display a single waveform or view all captured waveforms collectively on-screen.

Additionally, a robust history search function enables easy retrieval of waveforms that meet specific criteria from a large set of stored waveforms. Intuitive on-screen search tools allow users to define rectangular, full-waveform, or polygonal zones to isolate key parts of a waveform. If specific values, such as abnormal voltage levels or pulse widths, have been identified, users can also search directly by waveform parameters for quick access to relevant data.

Figure 4. History search function

Dual zoom windows enabling simultaneous viewing of different waveform sections

Multi-channel waveforms captured in long memory can be expanded both horizontally and vertically for detailed observation. The DLM series includes dedicated zoom keys and a knob for quick zoom-in on specific areas, with the option to use the touch screen for direct zoom control. Two zoomed waveforms with different time axis scales can be displayed simultaneously, offering versatile views for analysis.
The Auto Scroll function enables automatic scrolling of the zoomed area, allowing simultaneous viewing of different sections—such as the “cause” and “result” of an event—at varying magnification levels. This feature is invaluable for software debugging, as it allows precise examination of interconnected events.

Figure 5. Simultaneous zooming of two locations

Switching Loss Analysis

Calculate switching losses [ V ( t ) × i ( t ) ] based on voltage and current waveforms, with support for various analysis methods, including individual turn-on/off loss calculations, conduction losses, and long-duration losses over 50 Hz/60 Hz cycles. Additionally, using cyclic mode enables more precise analysis by allowing the integration range for loss calculations to be defined by each switching cycle.

Figure 6. Switching loss analysis screen

Power Analysis

Power parameters including active power, apparent power, reactive power, and power factor, can be automatically measured for up to four sets of voltage and current waveforms.
Performing Σ calculation of three-phase power using the twowattmeter method and statistical processing of the measurement results are available.

Figure 7. Measurement screen of power parameters

Other Multi-Channel Measurement Products

Features of the DL950 ScopeCorder

• Insulation input up to 1000 V
• 200 MS/s high-speed sampling
• Various plug-in modules and integrated measurement
• Real-time computation
• High noise resistance
• Trend display of the in-vehicle serial bus
• Simultaneous measurement up to 32 channels per unit
  *When four-channel modules are installed in 8 slots
• Multiple connections up to five units

Figure 8 The DL950 ScopeCorder and modules