Sine Wave Output Filter Architecture
Installed directly between the VFD PWM output stage and the motor leads. Cleans line-to-line pulse reflections and common-mode spikes before feeding long industrial cable runs or step-up transformers.
VFD Output Protection
Sine Wave Filters (Clean PWM Output)
Modern Variable Frequency Drives (VFDs) utilize Pulse Width Modulation (PWM) with high carrier frequencies that generate steep voltage rise times (dV/dt), high-frequency harmonics, and excessive peak voltage reflections. These phenomena cause winding breakdown, severe bearing fluting, acoustic noise, and premature failure of electric motors.
Prima Sine Wave Filters are engineered LC low-pass magnetic networks designed to convert harsh PWM square waves into a pure sinusoidal voltage with less than 5% total voltage distortion. By smoothing the output voltage, our filters eliminate cable reflection stresses, allowing conventional induction motors to run reliably even across long cable runs up to 15,000 feet.
- Eliminates motor insulation voltage stress
- Allows cable runs up to 15,000 ft (4,500 m)
- Dramatically reduces audible motor whine
- Eliminates the need for expensive shielded cables
- Efficiency rated greater than 98%
- Operates in ambients up to 60°C
Ratings & Parameters
Sine Wave Filter Performance Data
Service Load Conditions Conventional 3-Phase Motors & Submersible Pumps
Input Operating Voltage 380V to 600V (±10%), 3-Phase
Rated Current Range 2A to 500A Continuous Rating
Harmonic Voltage Distortion (THDv) <5% Maximum @ 2 kHz Switching
Inverter Switching Frequency 2 kHz to 12 kHz PWM carrier
Fundamental Frequency Range 6 Hz to 75 Hz (Up to 120 Hz derated)
Overload Capability 150% intermittent for 1 minute
Voltage Drop / Insertion Loss ≤6% Maximum at rated 50Hz / 60Hz
Maximum Motor Lead Length Up to 15,000 feet (4,500 meters)
Operating Ambient Temperature -40°C to +60°C (Modular open chassis)
Operating Altitude Up to 3,300 ft (1,000 m) without derating
Relative Humidity Tolerance 0% to 95% Non-condensing
System Integration
Application & Connection Topology
Engineered topologies for critical installations in oil & gas, chemical plants, wastewater facilities, and manufacturing automation.
Passive Harmonic Filter Input Architecture
Positioned on the utility line input of 6-pulse diode/SCR bridge rectifiers. Eliminates 5th, 7th, 11th, and 13th harmonic currents without excessive capacitive excitation at low-load levels.
Grid & Feeder Compliance
Passive Harmonic Filters (Adaptive Mitigation)
Non-linear loads such as variable frequency drives and rectifiers generate severe current harmonics that distort factory grids, overheat distribution transformers, cause false breaker tripping, and violate IEEE-519 regulatory standards. While conventional LC trap filters work adequately at full load, they frequently suffer severe degradation or cause leading power factor issues at partial loads.
Prima’s Passive Harmonic Filters utilize advanced Adaptive Passive Technology that continuously mitigates harmonics across broad load spectrums (from 20% to 100% capacity). The design ensures Total Harmonic Current Distortion (THID) remains below 6% at full rated power while preventing generator tripping during lightly loaded conditions.
- Meets IEEE-519 standards for harmonic current & TDD
- Guaranteed THID < 6% at rated operating power
- Safe for standby generator sets (controlled capacitive current)
- High short-circuit current rating (SCCR 100kA)
- Extended MTBF > 200,000 hours (Mil-HB-217F)
- Integrated thermal sensor switch (NO Contact)
Engineering Specifications
Harmonic Filter General Technical Parameters
Built strictly in compliance with IS 2026 / IS 11171, IEC 60076, and IEEE 519 standards.
| Parameter | Engineering Specification | Standard / Operating Condition |
|---|---|---|
| Nominal Line Voltage | 3× 380VAC to 500VAC (3-Phase) | Tolerance: 3× 342V to 550VAC |
| Operating Frequency | 50 / 60 Hz ± 1 Hz | Compatible with TN, TT, and IT systems |
| Motor Drive Power Range | 4 kW to 200 kW (Nominal Drive Input) | Custom configurations up to 500 kW |
| Drive Input Current Rating | 10A to 320A @ 50°C continuous | Filter input current: 7A to 360A |
| Total Harmonic Current Distortion (THID) | < 6% at full rated power | According to IEEE 519-2014 & 2022 |
| Partially Weighted Distortion (PWHID) | < 22% at rated power | Suppression of high-order inter-harmonics |
| Electrical Efficiency | > 98% at nominal voltage & power | Minimal thermal dissipation |
| DC-Link Voltage Stability | No load: +10% max | Full load: -5% max | Prevents over-voltage drive trip |
| High Potential Dielectric Test | 3000 VAC for 1 Minute | Insulation Class F (150°C) or Class H (180°C) |
| Short Circuit Current Rating (SCCR) | 100 kA prospective fault rating | Heavy industrial protection |
| Protection Degree & Enclosure | IP00 (Chassis) up to IP23 / IP54 (Enclosed) | Ventilated sheet steel, indoor / outdoor |
| Overload Capability | 1.6× rated current for 60s / hour 2.0× rated current for 10s / hour 5.0× rated current for 1s / hour | Engineered for severe inrush & start-up loads |
| Capacitive Current at Low Load | < 30% of rated current @ 400VAC < 37% of rated current @ 500VAC | Safe parallel operation with diesel generators |
| Environmental Temperature | -25°C to +50°C operational (100% load) +50°C to +70°C (with derating) | Storage: -25°C to +85°C |
| Calculated Operating Lifetime | Minimum 15 years continuous duty | MTBF > 200,000 hrs (Mil-HB-217F) |
| Safety Thermal Monitoring | Embedded over-temperature switch (NO contact) | Direct hookup to PLC or drive safety loop |
Selection Guidance
Engineering Comparison: Filters vs. Standard Reactors
Ensure your drive systems are fitted with the exact magnetic topology suited to your project scope.
| Criteria | Standard Line Reactor | Passive Harmonic Filter | Sine Wave Output Filter |
|---|---|---|---|
| Primary Function | Basic transient buffering & peak reduction | Total harmonic mitigation (IEEE 519) | Converts PWM pulses to clean sine wave |
| System Position | Input side of VFD | Input side of VFD (Line side) | Output side of VFD (Motor side) |
| THID Mitigation | Reduces THID to ~35% - 40% | Suppresses THID to <6% | Focuses on output THDv (<5%) |
| Max Cable Length | Not applicable (Input side) | Not applicable (Input side) | Extended up to 15,000 ft (4,500 m) |
| Motor Noise & dV/dt | No effect on motor stress | No effect on motor stress | Eliminates high dV/dt & audible noise |
| Typical Industries | Standard factory automation | Water treatment, HVAC, data centers | Submersible pumps, deep mining, oil fields |
Technical Queries
Frequently Asked Questions
Key technical and procurement questions answered by our power quality engineers.
What is the difference between a Sine Wave Filter and a dV/dt reactor?
A standard dV/dt reactor slows down the rate of voltage rise (reducing dV/dt to ~500-1000 V/μs) to protect motor stator insulation across moderate cable lengths, typically up to 300 to 500 feet. In contrast, a Sine Wave Filter is a full LC low-pass filter designed to clean the PWM output into a true sinusoidal waveform with less than 5% total voltage distortion. This allows motor leads to extend up to 15,000 feet without reflections, protects motor bearings from capacitive fluting, and virtually eliminates high-frequency motor whining.
How do Prima Harmonic Filters prevent issues with diesel generators?
Standard fixed-capacitor filters can cause a leading power factor under light-load conditions, which can lead to voltage instability or trip the automatic voltage regulator (AVR) of a standby diesel generator. Prima's Adaptive Passive design restricts capacitive current to less than 30% of rated current at light load (at 400VAC), allowing seamless, stable operation on utility lines and backup generator sets alike.
What data is required to size a filter for an existing or new VFD installation?
For Sine Wave Filters: operating line voltage, drive full load current (FLA), motor carrier/switching frequency (kHz), fundamental operating frequency range (Hz), and motor cable length. For Harmonic Filters: line supply voltage, drive kW/HP rating, nominal input current, and target THID/IEEE-519 standards.
Are custom enclosures and international certifications available for export?
Yes. Prima Transformers supplies both open-frame IP00 chassis units for panel builders and rugged IP20/IP23/IP54 powder-coated enclosures with built-in forced air cooling. All units comply with CE directives and relevant IEC/IS standards with complete routine and type test certificates provided upon dispatch.
Upgrade Your Power Quality & Protect Critical Motors
Whether you require custom-engineered Sine Wave Filters for deep submersible pumps or IEEE-519 Harmonic Filters for high-capacity industrial plants, our application engineering team is ready to assist with sizing and rapid technical quotes.
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