EMC CISPR 14 conducted emissions terminals

Question

I'm trying to improve my understanding of the CISPR 14.1 EMC test procedures and requirements, with a view to performing precompliance testing. In particular, I'm looking at conducted emissions measurements.

My understanding is that conducted emissions measurements are applied only to mains cables, but reading CISPR 14.1 I'm unable to confirm that this is the case.

Measurements in the 150 kHz to 30 MHz range are made on terminals:

Terminals are defined as conductive parts, suitable for re-usable electrical connection to external circuits

which I understand to also refer to connectors, not just terminal blocks.

There are additional stipulations as to which terminals the limits apply to, which in addition to the obvious mains supply terminals are:

On additional terminals of appliances as well as on load and additional terminals of regulating controls incorporating semiconductor devices the relaxed limits given for "additional terminals" in columns 4 and 5 apply.

No terminal voltage limits apply for leads, which are not easily extensible by the user (permanently connected, or provided with a specific connector), which are shorter than 2 m, and which connect the equipment with an auxiliary apparatus or device, (e.g. semiconductor speed controls, power plugs with AC-DC converters).

Our device has a 12 VDC solenoid mounted externally, connected by a specific connector and 1.5 m length of cable, but I don't think that the solenoid would be classified as an "auxiliary apparatus", which would indicate that it would require testing.

Here's a block diagram/simplified schematic. There are some electronics running off the 12 VDC too which control the relays.

I've searched for other CISPR 14.1 test reports to compare to, but none that I can find have any more terminals than just the power supply.

So what terminals/connections/cables does one actually apply conducted emissions testing to?

Answer 1

My understanding is that conducted emissions measurements are applied only to mains cables, but reading CISPR 14.1 I'm unable to confirm that this is the case.

CISPR 14-1 specifies conducted emission limits for both mains port and associated ports. It can be seen in table 5 of CISPR 14-1:2016. There is also a clause (4.3.3.7) for wired network ports which says these ports shall meet the CISPR 32 class B limits in the frequency range 150 kHz to 30 MHz.

CISPR 14-1 clearly states that conducted emission measurements are not only applied to the mains port.

Our device has a 12VDC solenoid mounted externally, connected by a specific connector and 1.5m length of cable, but I don't think that the solenoid would be classified as an "auxiliary apparatus", which would indicate that it would require testing. Edit: here's a block diagram/simplified schematic. There are some electronics running off the 12VDC too which control the relays.

As for the port you mentioned, you should check the Associated port clause (CISPR 14-1:2016 4.3.3.3) to decide if your port can be considered as an associated port. In this clause, it is indicated to which ports the test is not applied.

Answer 2

I try to share my knowledge with you, but I do not have references for this and I might be false on some topics:

First of all, you need to know how long the cables to your terminals are (not only mains, but all terminals). If its longer than 30 meters, then you have to do surge testing (lightning stroke tests), burst tests and of course conducted emission/immunity. If the cable of a port is between 3 and 30 meters, you can skip the surge tests. If a port has a cable <3m, you do not need any test (except ESD). Mains supply always needs full testing (because the lenght could be >30m).

So from my point of view, your solenoid does not need conducted testing, because the cable is <3m. But the other terminals need testing.