通电电机测试发现不正确的 VFD 设置

company

Easy Tool is an Italian supplier of condition monitoring solutions with a service and support office in Italy. Located in Fabriano, Ancona province, Easy Tool distributes ALL-TEST Pro condition monitoring instruments and provides regular condition monitoring services to a local gravure printing company specializing in food packaging materials. Gravure printing is a process where patterns are engraved onto plastic food packaging materials using specialized printing presses.

This food packaging and printing company hires professional condition monitoring personnel from the Italian company SPM Instrument to conduct on-site testing three times a year, analyze data trends, and provide support for its reliability program. In November 2015, field engineer Ettore Di Pasquale discovered an abnormal current waveform while performing dynamic testing on a 55 kW, 400 volt motor at the food packaging and printing plant.

 

application

This 55 kW, 400 volt motor is controlled by a variable frequency drive (VFD). The motor drives a centrifugal fan to deliver air to the natural gas burner. The gas burner requires a fan to provide the appropriate combustion air, while the steam generator requires a fan to provide heat to the drying section.

 

Discover

Di Pasquale connected the ALL-TEST PRO On-Line II™ motor tester to the switchboard to perform condition monitoring tests while maintaining a safe distance from the running motor. He quickly discovered an anomaly in the current waveform (see Figure 1).

Figure 1. Initial test results show the current waveform. Evidence indicates significant load fluctuations (peak at 6 amps, representing 20% ​​of the total load). These fluctuations were determined to be caused by improper configuration of the VFD controller and its PID controller.

“Di Pasquale explained, “Although there was no obvious cause for the alarm, the motor tests showed strong load fluctuations. “Load fluctuations occur when the variable frequency drive requires the motor to continuously change speed, even if the motor does not actually need to change speed while performing its intended function.”

Di Pasquale discussed this issue with managers at food packaging printing plants. He explained that when a frequency converter requires the motor to continuously change speeds, this activity puts significant stress on the motor mechanics and windings. If the VFD continues to change the motor speed in this way, over time, the motor may eventually experience rotor problems or winding failures.

 

Solution

To prevent motor failure, Di Pasquale recommended inspecting the VFD. The maintenance manager of the food packaging printing plant trusted Di Pasquale’s advice and contacted the VFD supplier. The VFD supplier came to the site and reprogrammed the VFD, adjusting it to correctly drive the motor.

 

Second round of motor testing

After the VFD supplier reprogrammed the VFD, Di Pasquale returned to the food packaging printing plant to conduct follow-up tests on the powered motor. He wanted to ensure that load fluctuations or abnormal waveforms no longer occurred. He then brought in the ATPOL II™ to confirm that the problem had been corrected.

The second round of energized motor tests using ATPOL II™ showed a significant improvement in load performance after VFD reconfiguration/PID correction (see Figure 2). The tests demonstrate that the VFD supplier correctly reprogrammed the VFD to drive the motor.

Figure 2. The energized motor test using ATPOL II™ shows that load performance is greatly improved after VFD reconfiguration/PID correction.

 

Lessons learned

1. The variable frequency drive (VFD) needs to be configured correctly. Improper programming of the VFD can shorten the motor’s lifespan over time due to incorrect operation.

2. Continuous condition monitoring is crucial for preventing equipment failures. This food packaging printing plant fundamentally prevents motor failures by having skilled condition monitoring technicians conduct regular tests and look for “red signals” indicating problems.

3. Several easy-to-use portable instruments, such as the ALL-TEST PRO On-Line II™ motor tester, can help you check the health of your motors. ALL-TEST II™ is a valuable monitoring and diagnostic tool that can help you see exactly what’s happening with your equipment. Ensure you have the appropriate tools to support your condition monitoring program.

Watch this video to learn how motor testing can save you time, money, and hassle, or visit www.alltestpro.com for more information.

 

About ALL-TEST Pro, LLC.

ALL-TEST Pro delivers on its promise of true motor maintenance and troubleshooting, featuring innovative diagnostic tools, software, and support to keep your business running. We support every ALL-TEST Pro product with unparalleled motor testing expertise, ensuring motor reliability in the field and helping maintenance teams everywhere maximize their productivity.

 

About Easy Tool

Easy Tool distributors of ALL-TEST Pro, LLC in Italy provide technical services, support, and training on condition monitoring practices, and offer a wide range of products, from high-tech portable instruments to online systems and comprehensive condition monitoring software. For more information, please contact [email protected].