Q62DA burnt out?

[sttchui]

Hi,

I having a mitsubishi PLC(Q00CPU) problem which it keep burnt the output(Q62DA) of this module which controlling a Honeywell motorized damper of a burner.

I have check the previous module, which the 1st channel is burnt i replace it with the second channel but this only last for a week or two

I have replace it with a new card, which work for maybe a week or two, the same thing happen.

This machine have been working for fews year already, running with problem until recently. i even change the motorized damper with a new one with same specification. But still the same problem exit.i even change the wire.

anyone have face a similiar problem? Is the any protection i can built to protect my analogue module, or is there leakage along the wiring?


thank you!

Regards

sttchui

 

[leitmotif]

Maybe too much load ie current on the output contacts? What are contacts rated for and what is load current.

I would control this with a relay and use a MOV to prevent coil collapsing field from damaging output contacts.

The other thing that comes to mind is if these are mechanical contacts on the output they do wear out. I would expect this to take more than a matter of weeks though.

Dan Bentler

 

[cjd1965]

This is an analog output card.

I would suspect an earth loop issue.. has any other equipment been added to the system recently?

 

[ATU]

Until you can track down the problem, put a fast acting fuse inline. Its much less expensive to replace the fuse than the analog module.

 

[sttchui]

thanks for the advice! anyway can you recommend any brand of this fast acting fuse easily can find in the market & cheap?

Thank you!

Regards

sttchui

 

[panic mode]

you have to make sure the wiring is sound. if you have moving cable, it may get damaged and possibly get intermittent short so check the cable and even if there is slightest suspicion of it's status, replace it. another common thing to check is how is load configured. analog inputs are tipically "voltage" that can be converted to "current" by putting shunt resistor (250 Ohm for example) in parallel with it. this resistor is usually part of the device and it is enabled by DIP switch or plug-in jumper or piece of wire connecting U and I terminals.
check it out, all you need is Ohm meter (should be part of every multimeter).

For example if the load is configured for current but you are driving it with voltage output, no wonder it smokes. every card will have it's limits. voltage outputs are usually rated for max current of 1mA or even less so maximum output of 10V would result of 40mA current on 250Ohm load (way too much).

i am not sure fuses will help since the current the analog output will tolerate is lower than smallest fuse I am aware of (have you seen fuse for 0.5mA for example). adding series resistor should be better protection (it's all in the Ohms law).

Next thing to check is grounding of both devices and potential diffreence because surge on the grid can cause problems. this is what 3-way isolated amplifiers are for. even if you smoke one of them, they are still much cheaper ($150-200 instead of PLC card that is in the order of $600-800).