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+1

COUT Minimum Current

Josh Holt 3 months ago in IQANdesign • updated by Joshua Holt 3 months ago • 3

Hello,


I am trying to run a Mitsubishi VFD that takes a current input of 4-20mA to change what hz the connected motor is running at. The VFD says it's not receiving a current command.

I see this excerpt in the manual:


Minimum current
There are several diagnostics methods that are active, one of these methods is based on
measuring current. The threshold for detection has been selected based on the
assumptions that currents below specified minimum current does not cause movement.
Error detection limits and delay
The COUT has two separate measurements of current, and is capable of detecting drift
faults on the closed loop control of the output. To avoid spurious trips, it is designed to
tolerate some deviation. The worst-case detection time for the most severe type of
faults are listed in the table below:
Since the MC4xFS COUT channels are grouped in pairs sharing an internal high-side
driver channel, shutdown of one COUT will cause shutdown of both COUT channels
in the pair. Restart conditions are controlled by the application.
Appendix B has detailed lists of failure modes focused on output wiring faults.
C4x-SMR-027:A Minimum current when using COUT
Safety related output functions controlled by COUT shall be designed so that
movement can only be activated if the output current is > 100 mA. 


Maybe I'm misunderstanding, but if the minimum current is 100mA, why does it let me set a COUT range of 4-20mA without throwing an error?


andyr 3 months ago

This topic has been answered a few times previously but to briefly reiterate once again:

The Iqan hardware current drivers are designed to drive current driven proportional control valves (pressure, flow, direction etc) which typically require currents of 200mA minimum . They are not for providing an industry standard current signal of 4-20mA as you need in your application as a demand input to your inverter. At present the Iqan platform hardware cannot provide this type of signal out ( although certain modules can now accept 4-20mA input signals.) There are third party Canopen to analogue output devices in the marketplace that will provide what you want for this application but as this is a Parker Iqan forum we cannot discuss them here ( use a search engine to look for Can to analogue signal converters)

+1
Luke@ARI 3 months ago

Hi Josh, this topic is probably a good candidate to submit as a bug. You're right, it doesn't give you an error or even a warning when you do a project check if you have a COUT set below what it can actually control.

This exact same thing for VFD speed control has bitten me in the past. I've been using these modules from IFM with great success:

https://www.ifm.com/us/en/product/CR3008

You use a PWM output on an IQAN module, and it gives you a scaled 4-20ma output. You have to do a little scaling / calibration in your code.


They also make a PWM to VOUT unit I've used, (as IQAN modules also don't do voltage outputs):

https://www.ifm.com/us/en/product/CR3004

Joshua Holt 3 months ago

Luke,

Thanks for the response. I ended up ordering what you suggested.

Thanks!

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