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Additionally, VFDs have the capability to also expand their data capture through external sensors via analog and discrete programmable inputs akin to traditional techniques but integrated [13]. For example, the ABB ACS880 drive includes three expansion slots, one of which is typically allocated for communication, while the remaining two can support analog option cards, enabling up to four additional 4–20 mA input signals [14]. In practical terms, these inputs can be utilized for vibration, temperature, flow, or other sensor types required by the application, eliminating the need for additional remote input capture devices and simplifying system integration. For the implementation presented below, using Modbus TCP/IP (noting that the drive manufacturer dictates the version) via Python to communicate with an ABB ACS880 VFD, it was essential first to select critical parameters, define their mapping structure, and establish their relevance to NDT [15–17]. Variable frequency drives continuously measure and log key performance indicators that correlate directly with potential failure modes [8,18]. Table 1 provides an overview of commonly available VFD parameters that offer insights into motor health and operating conditions. Table 2 illustrates how these parameters align with NDT methodologies.
Table1. Critical VFD diagnostic parameters.
Parameter
Modbus Register Address
Unit RPM VAC
Motor speed Motor voltage Motor current Motor power
400005 400007 400008 400009 400010 400011 400012 400013
Amps
kW Hz
Motor frequency Motor temperature DC link voltage Run time counter
C
VDC
Hours Note. This table presents the parameters for an ABB (2020) ACS880 and the corresponding Modbus TCP/IP addresses, emphasizing function codes three and 16-bit words. If the drive is not an ABB model or utilizes a different industrial protocol (as discussed in more detail later), the addressing scheme for the parameters will vary.
Table2. VFD failure mode comparisons.
VFD Parameter
Related Failure Mode Rotor eccentricity, load imbalance, overload, and underload Overheating and excessive torque Power quality issues, phasing, overvoltage, and undervoltage
NDT Relevance
Identifies excess electrical load, mechanical load, and application design quality
Motor current
Motor power
Detects energy losses
Identifies voltage transients, load motoring, and load regeneration
DC link (bus) voltage
Bearing wear, misalignment, load changes, stall, and overhaul
Detects irregular speed patterns
Motor speed
Note. The table introduces related failure modes and the relevance of NDT; however, the list and interpretation are subject to the application.
3. Data Transformation and Learning The integration of calculated metrics such as apparent power, efficiency, torque, and energy consumption expands the versatility of VFD data beyond basic motor control [11].
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