Mitsubishi Electric MELSEC iQ-R Series User Manual page 129

Action Take either one of the following two actions:
Action 1: To suppress the back EMF, connect a diode in parallel with the load under the back EMF influence (3).
• Sink output
Back EMF
Load
• Source output
Back EMF
Load
Action 2: Connect a diode into the path between the positive and negative terminals of the external power supply to provide a circulation
path. When simultaneously performing the action described earlier under "A load momentarily turns on when the external power supply is
powered on.", connect the diode in parallel with C1 and R1 (as shown in the dot frame of the figure below).
Page 125 A load momentarily turns on when the external power supply is powered on.
However, action 2 is not effective for the following source output modules because of the characteristics of the external power supply
circuit, so that take action 1 above.
• RY40PT5P
• RY41PT1P
• RY42PT1P
ON
OFF
D1 is in the following state.
• Reverse voltage VR (VRM): Approximately 10 times as high as the rated voltage in the specifications
<Example>
24VDC  Approximately 200V
• Forward current IF (IFM): More than twice as much as the maximum load current (common) in the specifications
<Example>
2A/1 common  4A or more
A load operates only by turning on the external power supply (transistor output).
Cause • The external power supply is connected with its polarity reversed.
Y0
COM
Output element
protection diode
• The reversed polarity may allow current to flow via the output element protection diode into the load.
Action Connect the external power supply with the correct polarity.
(3)
Back EMF
Load
Y0
(2)
Load
Y1
R1
12/24VDC
(1)
Shut off
D1
C1
COM
Load
Incorrect Correct
External
power
supply
9 TROUBLESHOOTING
9.3 Output Circuit Troubles and Corrective Actions
9
127