Installation Manual

Electrical & Electronic Application And Installation Manual
Production Release Version 1.0
Page 34
4.3 ECM Power Supply & Circuit Resistance
Often during engine cranking the battery voltage will drop to values much
lower than the normal system operating voltage. Under these special
conditions the ECM will operate with a minimum battery voltage of 7.3V. In
this mode the ECM has reduced functionality to enable the use of a low
supply voltage. It should be noted however that the ECM will reset and inhibit
starting if the voltage seen at its power pins drops to 5.5V or below. To
prevent excessive voltage drop ECM power supply circuit resistance must be
closely controlled. Once the engine enters ‘run’ mode the minimum ECM
voltage required to enable full ECM functionality increases to 9V.
The maximum permissible circuit resistance including positive and negative
wires is 50mOhms for 12V systems and 100mOhms for 24V systems,
however Perkins recommends that this value should not be targeted during
design, as it is often difficult to predict the final circuit resistance when
considering other factors such as fuse holders, connector resistance and
aging. A target calculated circuit resistance including wire and connections of
40mOhms for 12V systems 80mOhms for 24V systems is recommended. The
table below provides typical wire resistance for various cross sections of
copper wire.
Table 4.5 Typical ISO Conductor Resistance / m
2m
4m
6m
8m
10m
2 Ni-plated Copper 9.82 19.64 39.28 58.92 78.56 98.2
2.5 Ni-plated Copper 7.92 15.84 31.68 47.52 63.36 79.2
3 Ni-plated Copper 6.41 12.82 25.64 38.46 51.28 64.1
4 Ni-plated Copper 4.91 9.82 19.64 29.46 39.28 49.1
5 Ni-plated Copper 4.11 8.22 16.44 24.66 32.88 41.1
6 Ni-plated Copper 3.27 6.54 13.08 19.62 26.16 32.7
10 Ni-plated Copper 1.9 3.8 7.6 11.4 15.2 19
16 Ni-plated Copper 1.21 2.42 4.84 7.26 9.68 12.1
25 Ni-plated Copper 0.774 1.548 3.096 4.644 6.192 7.74
35 Ni-plated Copper 0.549 1.098 2.196 3.294 4.392 5.49
50 Ni-plated Copper 0.383 0.766 1.532 2.298 3.064 3.83
70 Ni-plated Copper 0.27 0.54 1.08 1.62 2.16 2.7
95 Ni-plated Copper 0.204 0.408 0.816 1.224 1.632 2.04
120 Ni-plated Copper 0.159 0.318 0.636 0.954 1.272 1.59
mohm/m at
20Deg C
Material
Conductor
CSA
mOhm at 20Deg C for Cable Length