Mitsubishi Electric MELSEC-Q Series User Manual page 52

(b) Description of the conditions 2) and 3)
• Vm: Supply voltage for the master module
Voltage
Recommended voltage 26.4VDC (24VDC +10%)
• V(V): Cable-to-cable voltage drop
V(V) = Transmission cable supply current I(A)  Cable resistance R()
Cable resistance R() = Cable length (m)  Conductor resistance (/m)  2
 Wire diameter 1.25  Conductor resistance 0.015/m
 Wire diameter 0.75  Conductor resistance 0.025/m
(c) Calculation example
The example shows how to check whether the total length of 100m is sufficient to configure a system in the
following conditions.
[Condition]
• Non-isolated slave module (Input ASLINKER)
Number of I/O points
Module current
consumption
Number of modules
• Connected load (three-wire sensor)
Three-wire sensor
current consumption
Number of sensors
Power supply voltage
• Wire diameter of transmission cables (DP, DN)
Wire diameter
• Power supply for the master module
Power supply voltage
[Calculation result]
Condition 1)
Condition 2)
Condition 3)
The calculation results 1) to 3) above show that no system can be configured.
However, a system can be configured by changing the power supply for the master module to 24.55VDC or
higher.
50
21.6 to 27.6VDC (24VDC -10% to +15%), ripple voltage 0.5Vp-p or lower
2 points
15mA
24
13mA
2
24VDC  10%
1.25
24VDC
(Ihin(A)  m) = I(A)  The maximum transmission cable supply current
(0.015 + (0.013  2))  24 = 0.984A  1A
Vm(V) - V(V)  20V
24 - (0.984  100  0.015  2) = 24 - 2.95 = 21.05V  20V
Vm(V) - V(V)  The lowest limit of the allowable voltage range for
connected load
The lowest limit of the allowable voltage range for connected load = 24
- 24  0.1 = 21.6V
21.05V < 21.6V
 Satisfied
 Satisfied
 Not satisfied