1–2 · HF Conducted Emissions
High-Frequency Conducted Emissions in Modern Plants
Modern facilities are dominated by fast-switching power electronics. Their steep voltage edges (high dv/dt) produce emission spectra extending into the MHz range.
Conducted emissions inside the facility network
Following Whitepaper v3.0.0: HF conducted emissions (150 kHz – 30 MHz) are injected by switching equipment and spread over the low-impedance DB and SMDB busbars, where they circulate into neighbouring machines. The facility transformer's high impedance at these frequencies keeps most of the noise inside the plant — so the heat appears on the machine side: in cables and windings through the skin effect, and in motor bearings through common-mode current.
Conducted emissions inside the facility network
01 · Switching equipment injects HF
VFDs, PV inverters, rectifiers and SMPS switch with steep dv/dt edges, injecting differential- and common-mode HF current (150 kHz – 30 MHz) into their supply cables.
Sites without their own transformer can pass part of this noise on to the utility panel and grid — that case is a separate example.
Where the heat appears (relative)
- Motor windings & bearings
- Machine cables
- DB / SMDB busbars
- MDB feeders
- Transformer & utility side
Heat generation threshold
Skin effect in machine cables & windings
The 50 Hz current uses almost the whole copper section (δ ≈ 9.2 mm). The HF current flows only in a thin surface skin (δ ≈ 0.17 mm at 150 kHz, 0.012 mm at 30 MHz), so its AC resistance — and its I²R heat — is far higher.
Skin thickness exaggerated for visibility.
Illustrative animation based on Whitepaper v3.0.0 — relative levels, not measured values.
Emission sources
Variable-frequency drives (VFDs)
PWM carrier frequencies of 2–16 kHz; steep dv/dt edges generate harmonics into the MHz range.
Switch-mode power supplies (SMPS)
Switching from 20 kHz to several hundred kHz, with fast transitions producing broadband emissions.
Solar PV inverters & rectifiers
High-frequency switching stages coupling conducted noise onto the AC network.
Frequency regimes
| Frequency regimes | Hz | Std. | |
|---|---|---|---|
| Low-order harmonics | < 2.5 kHz | IEEE 519 | Handled by harmonic filters and PF-correction capacitors |
| Supraharmonics | 2 – 150 kHz | IEC 61000-2-2 / research | Emerging regulatory range |
| Conducted emissions | 150 kHz – 30 MHz | CISPR 11 | Denka® Platinum Plate design band |
Quantified impact — peer-reviewed research
| Asset | Documented effect of HF distortion | Source |
|---|---|---|
| Induction motors — total losses | +8.7% to +19% total losses; +8.3 °C average winding temperature; ≈41 W extra loss per 1 °C rise in a 37 kW motor[5[5] Aarniovuori et al., IECON 2013Induction motor losses under converter supply (+8.7% to +19% total losses).,6[6] Jiang et al., 2022Winding temperature rise and additional losses under high-frequency harmonics.] | Aarniovuori et al., IECON 2013; Jiang et al., 2022 |
| Induction motors — iron losses | +29% under load, +86% at no load; up to +13 °C[7[7] Ding & Mi, 2011Iron losses in induction motors under PWM supply (+29% under load, +86% at no load).] | Ding & Mi, 2011 |
| Distribution transformers | Eddy-current losses up to +33%; insulation ageing 22% faster[8[8] Yaghoobi et al., 2020Distribution transformer eddy-current losses and insulation ageing under inverter harmonics.] | Yaghoobi et al., 2020 |
| MV/LV cables | Supraharmonic losses 1.6–2.4% of fundamental losses (>10–20% of harmonic losses); partial-discharge activity +10%[9[9] Novitskiy et al., 2020Supraharmonic losses in MV/LV cables.,10[10] Mariscotti & Mingotti, 2024Supraharmonics, cable losses and partial-discharge activity.] | Novitskiy et al., 2020; Mariscotti & Mingotti, 2024 |
| Insulation (all assets) | Arrhenius principle: insulation life roughly halves for every 10 °C temperature rise[3[3] IEEE Std 1-2000General principles for temperature limits in the rating of electrical equipment and for the evaluation of electrical insulation (Arrhenius thermal ageing).] | IEEE Std 1-2000 |
| Motor bearings | Bearings ≈51% of motor failures; HF common-mode current discharging through stray capacitances causes EDM pitting and fluting[4[4] IEEE Std 493 (Gold Book)Recommended practice for the design of reliable industrial and commercial power systems — motor failure statistics (bearings ≈51%).,11[11] Liu, 2014Bearing currents in inverter-fed motors.,12[12] Erdman et al., 1996Effect of PWM inverters on AC motor bearing currents and shaft voltages. IEEE Trans. Industry Applications.,13[13] ABB Technical Guide No. 5Bearing currents in modern AC drive systems.] | IEEE Std 493 (Gold Book); Liu, 2014; Erdman et al., 1996; ABB Technical Guide No. 5 |