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Maximum Allowable
Module Switch
Current
5
4
3
2
1
0
0
1 2 3
26 Getting Started
The Form C switch has an individual channel current specification of 5A.
However, if you apply 5A to all the channels with a relay contact resistance
of .25 Ohms, the power dissipation is 200 W. Since, for example, the
E1401B mainframe can only provide cooling for 55W per slot (to keep the
temperature rise to 10
A reasonable maximum current for the entire mainframe is 50A. That is,
10 channels each carrying 5A or some combination of channels and
currents that total 50A. This will produce about 67.5 W of internal dissipation,
leading to an approximate 15
Figure 1-14 shows a typical way to derate the channels, in terms of current
throughout the channels, to keep internal power dissipation under 45 W and
67.5 W or 10
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
=45 Watt MF Diss
=67.5 Watt MF Diss
Figure 1-14. Typical Form C Switch Allowable Switch Current
o
C), this cannot be allowed to happen.
o
C temperature rise.
o
o
C and 15
C temperature rise, respectively.
E1401B Mainframe and
.25
Relay Contact Resistance
No. of Switches Carrying Current
Chapter 1
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