MDA-550 test meter tool


Motor systems are critical to the function of many types of industrial facilities, often comprising a majority of a plant’s energy expenditure. As such, motor drive malfunctions can be catastrophic. Preventative maintenance is the key to keeping motor drives operating at their best for the duration of their working life. In doing so, you protect your facility against unnecessary energy expenditures and premature equipment failure.

The MDA550 test meter is designed to facilitate easy testing to keep motor drives running smoothly. As a preventative maintenance tool, the MDA550 analyzes voltage and current signatures so that you can respond to elevated signals before they become a serious problem.

The MDA550 Test Meter Tool

When more in-depth troubleshooting is necessary, the tool will guide users through a set of five comprehensive performance tests that assess functions from input to output. There’s no need for guesswork or multiple test devices—the MDA550 uses descriptive on-screen prompts to show you exactly what’s going on within your motor drive so that you can rapidly identify areas of concern.

At Renown Electric, we understand the importance of maintaining fully operational electrical systems, but we also understand how challenging that task can be. As experts in motor repair and servicing, we can help you identify products like the MD550 that can simplify preventative maintenance and keep your facility’s equipment running at full capacity. We also specialize in rapid, skilled repair of motor systems in the event you do experience a malfunction.


Industry-Leading Expertise from Renown

As a leader in predictive and preventative maintenance surrounding VFD performance and repair, our team of professionals first would first provide an initial signature of the drive. This includes measurement and analysis of key motor-drive parameters including, but not limited to

  • Voltage
  • Current
  • DC Bus voltage level
  • AC ripple,
  • Unbalance & Harmonics,
  • Voltage modulation,
  • Motor shaft voltage discharges + common mode current

Once this analysis is concluded by one of our professionals, we would provide a comprehensive report, accompanied by frequent follow-ups depending on various factors, such as how critical the drive is and compare the data during each inspection to that of previous inspections to review the systems health and provide a consultation or service of any further preventative maintenance deemed necessary for safe and optimal performance.

MDA550 Key Features

The MDA550 Test Meter Tool

Traditional testing protocols are time-intensive and often require a specialist’s guidance. Technicians typically use multiple testing devices in their assessments, so results are rarely consolidated into an organized historical record that can be used for future troubleshooting. These limitations can make it difficult to justify regular testing as a component of preventative maintenance.

The MDA550 was engineered specifically to address these problems, making regular testing more accessible for facility managers. Each key feature resolves one or more limitations of traditional motor drive testing. These features include:

  • The main functionalities of a meter, handheld oscilloscope, and recorder, all contained within the same device.
  • Clearly guided testing protocols, including step-by-step voltage and current connection diagrams to facilitate setup.
  • Pre-defined measurement profiles for each procedure, minimizing the complexity involved in configuring test devices.
  • Onboard report-writing capabilities that generate as-found and as-left troubleshooting reports.

This suite of tools makes the MDA550 one of the most comprehensive testing tools on the market.

Five Tests for the MDA550

There are certain tests that are critically important to both preventative maintenance and troubleshooting. The MDA550 is designed to perform all five of the following important analyses:


  • Drive input. The first potential source of disturbances is the feeder circuit into the motor drive. This test assesses the power entering the motor drive to determine if there are any distortions, or if there is noise that could affect the power ground.
VFD Input diagram
  • DC bus. The next test assesses the motor drive’s AC/DC conversion functionality. For ideal performance, the drive must operate within specific voltage parameters and with adequate smoothing. High ripple voltage can be a warning sign of component failure or other building problems within a drive. Testing AC/DC conversion can help identify these sorts of problems in the capacitors and can indicate if the connected motor is sized correctly.
DC bus diagram
  • Drive output. The drive’s output is obviously another critical parameter, and its functioning can give clues to the overall health of the motor drive. If there is a problem with output, there is likely a problem with the drive’s circuitry.
VFD output
  • Motor input. Moving into the motor itself, the next test analyzes voltage at the motor input terminals. Inconsistent voltage or incorrect cable selection can result in voltage spikes that damage both the motor drive and the motor. These input tests are largely the same as those performed on the motor drive, but it’s still essential to test both sites, especially when attempting to localize a problem.
  • Motor shaft voltage. The final test is designed to detect voltage pulses in the rotor shaft. These harmful spikes occur when voltage from the motor drive couples with voltage from the motor’s stator or rotor, causing flashover currents or sparking. Physical damage can also occur from these flashes, including pitting and fluting of the motor bearing race, which is known to cause premature motor failure. Regular assessments of motor shaft voltage make it easier to detect these sorts of problems before they cause motor defects.

While all of these tests are useful on their own as troubleshooting tools, they are most useful when included in a comprehensive preventative maintenance program. When performed consistently, these tests offer benchmarks for a system’s typical function, providing a voltage/current signature analysis for a given motor system. Then, if a variation is detected, there is time to correct the malfunction before it compounds into a more significant problem.

Advanced users can also take advantage of the MDA550’s additional testing features, including harmonic measurements and voltage modulation, to gain additional insight into a motor’s performance.

Using the MDA550

One of the key design concerns in developing the MDA550 was ease-of-use. With its fully-guided troubleshooting processes and detailed diagrams, the device is completely intuitive and far easier to operate than standard electrical tools. As a result, not only can more employees confidently perform routine tests, but decision-makers can act more quickly on aberrant measurements.

MDA550 users can take advantage of the following measurement and assessment capabilities:

Motor Drive Health Indicators

The MDA550 provides quick and accurate reads of:

  • Voltage
  • Current
  • DC Bus voltage level and AC ripple
  • Voltage and current balance
  • Harmonics
  • Voltage modulation
  • Motor shaft voltage discharges

Extended Harmonics Measurements

The MDA550 identifies the impact of harmonics and harmonic pollution on a motor system, with the capability to perform extended measurement of:

  • 1st to 51st harmonics
  • 1 to 9 kHz
  • 9 to 150 kHz

Guided Measurements

Receive detailed, illustrated instructions to guide you through measurements of:

  • Motor-drive input DB bus
  • Drive output
  • Motor input
  • Motor shaft voltage

Additional Capabilities

Other time-saving features included in the MDA550 include:

  • Simplified measurement setup with profiles to regulate automate data collection.
  • Quick and easy creation of troubleshooting reports for historical records and collaborative purposes.
  • A full range of meter, recording, and oscilloscope capabilities for use on industrial systems.

To learn more about our offerings and how they can benefit your operation, get in touch with our expert team today.