What is the current rating of the Y113xA cables?

The Y1135A and Y1136A cables are 50 conductor, 24 AWG cables with 25 shielded twisted pairs with PVC insulation. They can be used with the 34921A, 23A, 25A, 31A, 32A, 33A, 37A, 38A, 51A, and 52A plug-in modules for the 34980A. However, they do not support the full rated total current of the 34937A and 34938A.

The Y1137A and Y1138A cables are 78 conductor cables 28 AWG conductors with 39 shielded twisted pairs. They can be used with the 34922A, 24A, 34A, 39A, and 34950A plug-in modules.

Executive Summary: (Based on the minimum rating of the two references listed below)

For the Y1135A/36A DB50 cables with a 35 C rise above ambient:
• 1.3A max per conductor with 41+ conductors used
• 1.5A max per conductor with up to 40 conductors used
• 2A max per conductor with up to 30 conductors used
• 2.7A max per conductor with up to 15 conductors used
• 3A max per conductor with up to 5 conductors used
• 3.7A max per conductor with up to 3 conductors used

For the Y1137A/38A DB78 cables with 35 C rise above ambient:
• 0.83A max per conductor with 41+ conductors used
• 0.88A max per conductor with up to 40 conductors used
• 1.10A max per conductor with up to 30 conductors used
• 1.54A max per conductor with up to 15 conductors used
• 1.76A max per conductor with up to 5 conductors used

References:
http://alphawire.com/en/ResourceCenter
http://www.coonerwire.com/amp-chart/

The Cooner Wire Amp Chart rates the cables at 80 C which is the maximum temperature rating of the PVC insulation used. At 80 C for 1 to 3 conductors the Cooner rating is 5A
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Y1135A/36A DB50 cable limitations:

• When used with 34937, there are fourteen 1 A switch (2 A carry) form C channels and two 5 A switch (8 A carry) form A channels for each of the two banks for a total of 16 channels which use a total of 46 conductors. Only two conductors are used at a time on the 14 form C channels and the form A channels also use two conductors, so only 32 conductors can be used simultaneously.

For 30 conductors, the rating is 2 A. It should be safe to increase the temperature slightly and use 32 conductors. For up to 3 conductors, one switch, the rating is 3.7A.

• When used with 34938, four conductors are used for 16 of the 20 channels, bringing the DB50 cable rating to 3 A max for a single one of these 16 switches. 4 channels (4, 9, 14, and 19) use six conductors. One of these channels can be used for up to 5.3 A. If all 20 switches were closed, the maximum current per channel would be limited to 1.5 A.

The Y1135A/36A do not support the 5A switch/8A carry rating of the high current channels of the 34937A and 34938A. Keysight does not provide cables that meet these limits.