3-Phase Output Chokes

Pulse Width Modulation (PWM) signals from IGBT-based drives generate a wide spectrum of high-frequency harmonic content at the motor terminal. These harmonics lead to increased core losses, elevated copper heating, and acoustic noise in motors and transformers. An appropriately rated 3-phase output chokes introduces a controlled series inductance between the inverter and load, forming an RL low-pass filter that suppresses higher-order harmonics. This results in improved waveform integrity and reduced electromagnetic interference propagated through the system. 

Rated System Voltage

400 V / 415 V / 480 V / 690 V AC

Rated Current Range

10 A to 1000 A

Operating Frequency

0 to 150 Hz (suitable for full VFD output spectrum)

Typical Inductance Value

0.1 mH to 5 mH (based on motor rating and dV/dt limitation requirement)

Inductance Tolerance

±5% (measured at rated frequency and current)

Product Description

Voltage slopes at the motor terminals frequently exceed 5000 V/µs in modern high-speed switching drives. Such steep transitions accelerate partial discharge phenomena, particularly in motors with standard insulation not designed for inverter duty. An output choke imposes a finite inductive impedance, which moderates the voltage rise time without altering the inverter’s fundamental frequency output. This ensures compatibility with legacy motors or installations with insufficient insulation margins. 

Core Material

Low-loss CRGO / Fe-based Amorphous Alloy

Switching Frequency Capability

Up to 20 kHz

Maximum Temperature Rise

≤ 80°C over ambient at full load (as per IEC 60076-6)

Insulation Class

Class H (180°C rated thermal insulation)

Dielectric Strength

3 kV AC for 60 sec between winding and core

Magnetic Flux Density (Bmax)

≤ 1.5 Tesla at rated load, below non-linear saturation region

Harmonic Current Handling

Up to 200% of fundamental current

Common Mode Attenuation

Reduces shaft voltage and bearing current effects by filtering common-mode voltage

Short Circuit Withstand Time

Reduces shaft voltage and bearing current effects by filtering common-mode voltage

Cooling Type

Natural air-cooled; forced cooling available for high-current applications

Acoustic Noise Level

≤ 60 dB at 1 meter under rated PWM loading conditions

Technical Advantages

Cable lengths exceeding 15 meters often result in voltage reflection and constructive interference, leading to terminal overvoltages that surpass rated winding limits. This effect is especially pronounced when motor impedance differs significantly from the cable characteristic impedance. Output chokes reduce the rate of current change (di/dt) and shift the resonance point of the cable-load system, thereby attenuating the amplitude of reflected wave voltages. The result is a controlled voltage profile that complies with IEC insulation coordination levels. 

Conducted emissions from inverter outputs can couple into control systems or communication lines, especially in installations with inadequate shielding or bonding. Output chokes provide distributed reactance that diminishes common-mode and differential-mode EMI without reliance on ferrite-based suppression. The construction of the choke, including winding technique and magnetic core design, directly influences its effectiveness in mitigating emissions within CISPR-11 Class A and B limits. 

 

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Industry Applications

Elevator and Hoist Control Panels

Dampens reflected wave voltages in long cable runs, preventing overshoot conditions and shaft bearing damage. 

Textile Machinery with High-Speed Drives

Provides stable inductive filtering to manage rapid switching transients and mitigate torque pulsation effects on delicate equipment. 

HVAC Systems with Long Cable Runs

Controls transient voltages and reduces harmonic content to maintain power quality at fan or compressor motor inputs. 

CNC Machine Tools with Precision Spindles

Attenuates PWM noise and limits common-mode currents to protect encoder systems and spindle motor windings. 

Pumps and Compressors in Process Plants

Ensures controlled motor startup and sustained harmonic suppression under continuous and cyclic loading conditions. 

Cranes and Material Handling Drives

Handles frequent torque reversals and regenerative braking energy without saturation or thermal imbalance across windings. 

 

3-Phase Output Chokes

Thermal Stability Under Nonlinear Load Profiles

Drives feeding variable-torque or cyclic-load motors introduce irregular current waveforms, causing localized heating in conventional inductors. 3-phase output chokes built with low-loss, high-saturation flux density magnetic materials maintain thermal uniformity even under conditions of unbalanced loading or intermittent overload. Advanced thermal modeling and forced cooling designs ensure that hotspot formation is minimized, allowing operation within Class H temperature rise limits without thermal derating. 

Switching frequencies above 10 kHz significantly increase switching losses and electromagnetic noise when using standard chokes with insufficient frequency response. 3-phase output chokes designed with reduced core losses at higher frequencies and precision-wound interleaved coils maintain effective inductance across a wide spectrum. This ensures that inverter performance, including modulation index and voltage control, remains stable while preserving output signal fidelity. 

 

3-Phase Output Chokes

Having Doubts? Our FAQ

Check all our Frequently Asked Question

How does Frigate ensure inductance stability across load variations in 3-phase output chokes?

Frigate uses high-grade magnetic cores with low hysteresis and minimal temperature drift. The chokes maintain consistent inductive impedance under both linear and non-linear loads. Advanced coil geometry prevents saturation even during high peak current events. This ensures waveform integrity and reduced harmonic distortion across all load conditions. 

What core materials does Frigate use to prevent thermal runaway in high-frequency switching environments?

Frigate selects low-loss silicon steel or nanocrystalline materials based on application voltage and switching frequency. These materials exhibit low eddy current loss and excellent thermal conductivity. Core saturation and localized heating are minimized even above 10 kHz switching rates. This enables reliable choke performance in modern IGBT-based drives. 

How are Frigate's 3-phase output chokes optimized for inverter systems with long cable lengths?

Frigate designs chokes with tuned inductance values that reduce reflected wave overshoots at the motor terminals. This minimizes voltage doubling caused by impedance mismatches in long cable runs. Chokes are tested using time-domain reflectometry (TDR) to verify waveform behavior. The result is enhanced motor insulation life and safer terminal voltage levels. 

How does Frigate mitigate acoustic noise in motors using output chokes?

High-frequency harmonic content excites mechanical vibrations in motor windings. Frigate’s output chokes filter these harmonics before they reach the motor. This reduces magnetostriction-related hum and vibration. Lower noise levels also indicate reduced core and copper losses. 

What thermal insulation class does Frigate use in 3-phase output choke windings, and why?

Frigate uses Class H insulation (180°C) for all winding materials. This allows safe operation under high ambient temperatures and intermittent overloading. Thermal modeling ensures winding temperature stays within design limits during steady-state and transient conditions. This extends choke life without requiring external cooling. 

 

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LOCATIONS

Registered Office

10-A, First Floor, V.V Complex, Prakash Nagar, Thiruverumbur, Trichy-620013, Tamil Nadu, India.

Operations Office

9/1, Poonthottam Nagar, Ramanandha Nagar, Saravanampatti, Coimbatore-641035, Tamil Nadu, India. ㅤ

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3-Phase Output Chokes

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