CISPR 25:2016 CEV-HV Limits

Conducted Emission – High Voltage Voltage Method (Table I.1)

This table summarizes the Conducted Emission (CEV-HV) voltage method limits (corresponding to Table I.1) for automotive high-voltage (HV) components per CISPR 25, suitable for EMC pre-compliance and certification reference.

Limit Visualization Curve

Envelope

Class:

Filter Table by Class:

Levels in dB(µV). Scroll horizontally to view more.

Service / Band	Frequency MHz	Class 5			Class 4			Class 3			Class 2			Class 1
Service / Band	Frequency MHz	Peak	QP	Avg	Peak	QP	Avg	Peak	QP	Avg	Peak	QP	Avg	Peak	QP	Avg
BROADCAST
LW	0.15 to 0.30	107	94	87	117	104	97	127	114	107	137	124	117	147	134	127
MW	0.53 to 1.8	84	71	64	92	79	72	100	87	80	108	95	88	116	103	96
SW	5.9 to 6.2	77	64	57	83	70	63	89	76	69	95	82	75	101	88	81
FM	76 to 108	50	37	30	56	43	36	62	49	42	68	55	48	74	61	54
TV Band I	41 to 88	47	-	37	53	-	43	59	-	49	65	-	55	71	-	61
MOBILE SERVICES
CB	26 to 28	61	48	41	67	54	47	73	60	53	79	66	59	85	72	65
VHF	30 to 54	59	46	39	65	52	45	71	58	51	77	64	57	83	70	63
VHF	68 to 87	51	38	31	57	44	37	63	50	43	69	56	49	75	62	55

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Test Setup & Technical Overview (HV)

Detailed engineering guide for High-Voltage Conducted Emissions (CEV-HV) by Voltage Method

Technical Overview: HV Systems and Decoupling Classes

In electric (EV) and hybrid vehicles (HEV), high-voltage (HV) components generate fast switching transients that can couple into the low-voltage (LV) domain, threatening sensitive onboard receivers. CISPR 25 Annex I defines high-voltage conducted emission limits (Table I.1) and HV-LV decoupling classes.

The decoupling class (Class A1 to Class A5) is not an external circuit in the test setup, but a rating of the coupling attenuation (isolation) between the EUT's own HV and LV ports. Class A5 represents a very high decoupling performance (coupling attenuation of at least 40 dB, reflecting excellent internal filtering and shielding design). Consequently, devices meeting Class A5 decoupling are allowed more relaxed conducted voltage limits on their HV terminals.

Test Configuration: Dual HV-ANs and Grounding

High-voltage conducted voltage measurements are performed using High-Voltage Artificial Networks (HV-ANs) to capture disturbance voltages on the terminals. Since HV supply cabling is typically a shielded two-conductor (positive and negative) bundle, the test configuration requires one HV-AN in the positive line and a second HV-AN in the negative line (2 HV-ANs in total).

The receiver scans one HV-AN port at a time while the unused port is terminated with a 50 Ω load. The shield of the HV cable must be securely bonded at both ends to the reference ground plane with low RF impedance to maintain path stability and prevent shield leakage from causing false peak failures.

Interpretation of Limits (Class 1-5)

CISPR 25 specifies five limit classes (Class 1 to Class 5), with Class 5 being the most stringent. The selection of the limit class does not depend on whether a component is high-voltage or high-power, but rather on its physical installation location and proximity to sensitive vehicle receivers and antennas.

Even for major HV units like traction inverters, an OEM may specify Class 3 or Class 4 if they are installed in well-shielded compartments far from antennas. Class 5 is strictly mandated only when components reside near antenna systems or under extreme OEM EMC requirements to protect safety-critical communication bands.