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VFD Monitoring

Summary

Verivolt provides reliable sensing solutions for Variable Frequency Drive (VFD) monitoring and testing by offering high-bandwidth, low-noise, and fully isolated voltage and current sensors. Our sensors are engineered to meet the demanding requirements of VFD applications, ensuring accurate, safe, and stable performance in high-frequency and high-voltage environments.

VFD Monitoring

The Challenge: 

Voltage and Current Monitoring in VFD Systems

Variable Frequency Drives (VFDs) are widely used across various industries to optimize motor performance, enhance energy efficiency, and improve process control. VFDs are commonly found in manufacturing, HVAC systems, water and wastewater treatment, oil and gas, among many others. These applications often involve demanding electrical and environmental conditions, including high currents and voltages required to power motors. Additionally, such environments may expose equipment to high ambient temperatures, electrical noise from switching elements, and mechanical vibrations. Monitoring voltage and current in VFD applications is critical for performance verification, troubleshooting, and preventive maintenance.

Most modern VFDs have embedded sensors that measure current and voltage internally. These internal measurements are primarily used for control logic, protection mechanisms, and sometimes diagnostics. However, there are several good reasons to use independent current and voltage sensors to monitor the motor or load, even if the VFD already has built-in sensing, such as:

Accuracy and Signal Quality

VFD sensors are often optimized for control, not high-resolution or high-accuracy monitoring. External sensors can: 

• Offer higher accuracy
• Be calibrated independently
• Provide better linearity and frequency response
• Output analog signals suitable for external data acquisition systems (DAQ, SCADA, etc.)


Accurate Power Measurement 



Advanced Analysis & Logging



Third-Party Compliance & Certification 



Retrofit & Test Bench Applications



How do Verivolt’s Sensors Address these Challenges?















Conclusion 













To calculate true power (P = V × I × cosφ), you need both current and voltage measurements. Independent sensors allow real-time power and energy monitoring, including active power (Watts), reactive power (VARs), apparent power (VA) and power factor (cosφ) which are essential for: 

• Energy efficiency audits
• Load profiling
• Cost allocation
• Diagnosing power quality issues



VFDs may not provide raw waveform access (especially with high sampling rate), long-term logging and custom data formats or protocols for integration. Independent sensors allow for:

• Real-time waveform capture
• FFT-based harmonic analysis
• Custom integration with other automation or monitoring systems




Power quality standards or ISO audits may require certified external measurement tools. Independent sensors ensure traceable calibration and compliance with standards like:

• IEC 61000 (power quality)
• IEEE 519 (harmonics)
• ISO 50001 (energy management)





For testing motors with different VFDs or changing loads, independent sensors:
• Avoid dependency on each VFD’s interface
• Enable standardized data acquisition across brands/models
• Provide portable, reusable instrumentation


 



Verivolt sensors used in this application field present the following characteristics.

Characteristics 
Importance in VFD Application
High accuracy (0.1%)
Precise voltage and current measurement (<±0.1%) is critical for performance validation, efficiency analysis, and detecting unbalance or faults in motor control.
High bandwidth (100 kHz to several MHz)
Required to accurately capture high-frequency PWM output waveforms from the VFD and detect fast transients or voltage overshoot.
Galvanic isolation
Protects measurement systems and operators by electrically isolating the sensing system from high-power circuits; critical in industrial VFD environments.
High CMRR (Common Mode Rejection Ratio)
Needed for accurate differential voltage measurements in noisy environments like motor drives.
Low delay
Fast-reacting sensors are necessary for capturing real-time PWM signals used by VFDs. Low latency ensures accurate phase alignment between signals and responsiveness for control loops and dynamic testing.
Wide temperature range
Allows reliable measurements in harsh industrial environments with high ambient temperatures, often near motors or inside enclosures.
Compact Form Factor
Important for integration inside control cabinets or motor housings, where space is limited.
Certification traceability 
(e.g., ISO 17025-calibrated)
Needed for test traceability and compliance in certification programs.



Verivolt delivers precision voltage and current sensing solutions tailored for the dynamic requirements of VFD systems. Our sensors provide the performance, accuracy, and isolation needed to ensure optimal motor monitoring. Visit our website to explore products designed to meet the evolving challenges of this industry.



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