Chokes and filters in HVAC applications

Variable Speed Drives (VSDs), commonly used in modern HVAC systems to control fans and pumps, can introduce electrical harmonics, voltage spikes, and electromagnetic interference (EMI), which reduce reliability and increase operational costs.

To address these issues, harmonic reduction chokes, motor chokes, and sinewave filters are vital. Line chokes minimise total harmonic distortion (THD), improving energy efficiency and helping installations comply with EMC standard EN 61800-3. Motor chokes and sinewave filters reduce electrical stress on motors by converting VSD pulse-width modulation into a near-sinusoidal waveform. This improves motor life, lowers bearing currents, reduces EMI, and cuts noise — especially beneficial in hospitals and offices.

The rise of IP65/66-rated VSDs presents integration challenges due to the limited internal space for chokes, often necessitating the use of additional enclosures with thermal management capabilities. Compact, high-IP-rated external chokes are needed to ensure compliance and performance in harsh environments.

Long cable runs, common in large HVAC installations, increase dV/dt stress and EMI. Sinewave filters and line reactors help manage these issues by reducing voltage spikes and EMI emissions, potentially eliminating the need for shielded cables.

Chokes and filters are crucial for maintaining the efficiency, reliability, and compliance of HVAC systems. Manufacturers should provide tailored solutions, particularly for compact, high-IP-rated drives used in conjunction with extended cable runs.

www.reo.co.uk