Hi,
I am building a cable with connector Phoenix Contact 1803659, the connector can fit up to 16 AWG cable.
(Available at: https://www.phoenixcontact.com/online/portal/us?uri=pxc-oc-itemdetail:pid=1803659&library=usen&tab=1)
My application is a 6A pulse mode of <50ms or 12A DC pulse mode of <20ms, so I have looked up to Belden Inc. products, as some previously used products are from Belden Inc. as well.
A product I have found is MPN: 8465 06100 (BEL1093-100-ND), but I am not sure if this cable is suitable because the Max current rating in datasheet mentioned is 4A.
Please suggest if this cable rating is able to support my application, or suggest any better part.
Thanks in advance.
The problem you’re hitting is the temperature rise of small gauge wires. Belden, and most other wire manufacturers, use a standardized fire safety current rating that assumes a continuous current flow. They are also assuming specific targets for ambient temperature and many other factors
The Belden technical information section of their catalog shows how they calculate the current carrying capacity (page 22.4). https://info.belden.com/hubfs/resources/technical/catalogs/cabling-solutions-for-industrial-applications-catalog-technical-information-section.pdf (4th page of this PDF extract).
The Belden current carrying calculation is designed so that non-qualified engineers can choose a wire gauge for the current they have to carry and be certain that there will be no fire danger in just about any installation on planet Earth.
A qualified engineer can take into account the factors for the specific application and may come up with a much higher safe current rating while still maintaining fire safety.
For your specific application the short pulses will likely allow much higher currents. However it will depend on the maximum frequency of the pulses, maximum ambient temperature, minimum amount of airflow around the cables, and other factors.
Since getting this calculation correct is a fire safety issue, I recommend you consult with the original designer of the circuitry this cable assembly is used with and get a wire gauge specification instead of a pulse current rating.
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We would need more details on the application?
I have been advised the following by Belden’s Technical Support Team:
Belden cannot recommend a cable construction based on this information, to make a good recommendation, please get more information about the application that the cable will be used in. (The PCB, assembly, Chip, camera, light, etc…). A 6A pulse mode of <50 ms does not give me enough information to know what the overall power usage will be (is it 50 ms on, 950 ms off? 50 ms off? 5 ms off? This would determine how much power is actually flowing through the cable.)
As a note, a cable could have more power pass through it at lower temperatures and still be OK, because as the cable heats up, the ambient environment will help cool it. It’s the same idea of how a laptop gets much hotter if you leave it outside in the sun in summer, vs when it’s inside in an air conditioning.
Yes. As mentioned, information regarding off-time is needed in addition to on-time.
The cable is rated at 4A per conductor; within limits any waveform resulting in an RMS current flow of 4A or less should be acceptable. In terms of square pulse waveforms such as described, this means that the maximum permissible duty cycle for peak current IPeak is (IRated/IPeak)2
(4/6)2=0.44 Thus, for the 6A, 50ms case an off time of 64ms minimum would be required. Similar math for the 12A, 20ms case indicates a minimum 160ms off time.
The thermal mass of the cable imposes limits on how far this principle can be extended; there would likely be problems if time here were measured in days rather than milliseconds for example.
