Are you monitoring the 230VAC source to ensure it does not go outside digital input specifications for the DI module?  For example, let's say the spec is 230VAC ±10%, the input voltage should stay within the range of 207-253VAC.  Let's say for whatever reason, the voltage surges every morning to +15% around 5AM local time.  Over time, that DI module will eventually start to fail on the most susceptible inputs that are least able to tolerate out of spec conditions.

If you know for certain the voltage is always within the specs (whatever they are), you should contact Siemens directly using their "Support Request" link above these online forums in the gray bar and create a new request and ask them.

If your process cannot tolerate these failed DIs, consider converting the 230VAC signals to 24VDC signals using (opto-isolated) voltage converters.  That's just my years of experience speaking when I know no matter how good the power is, there will be times when unexpected things happen to the AC bus, or when large ~230VAC loads go offline and kick-back on the 230VAC supply, temporarily raising the 230 VAC supply - often well above spec.

I also know from many years using S7-1200/1500 devices, the 24VDC inputs have the most robust protections built in and I rarely experience problems even when the inputs exceed the specs by a good margin.

M_Sultan

We are experiencing a recurring issue with the DI 16x230VAC 6ES7521-1FH00-0AA0 channels in some of our remote I/Os in the field. These channels are frequently getting damaged.

When a channel is damaged, it exhibits flickering behavior, turning on and off at a high frequency. Upon checking the current, I found that the damaged channels are drawing less than 4 mA, while functioning channels should show a current greater than 10 mA.

What could be causing this issue, and how can we protect the channels to prevent further damage?

M_Sultan

What could be causing this issue, and how can we protect the channels to prevent further damage?

Quick solution: Introduce galvanic isolation for that input if possible. 

Thank you for your response.

0_Einstein

Are you monitoring the 230VAC source to ensure it does not go outside digital input specifications for the DI module?  For example, let's say the spec is 230VAC ±10%, the input voltage should stay within the range of 207-253VAC.  Let's say for whatever reason, the voltage surges every morning to +15% around 5AM local time.  Over time, that DI module will eventually start to fail on the most susceptible inputs that are least able to tolerate out of spec conditions.

If you know for certain the voltage is always within the specs (whatever they are), you should contact Siemens directly using their "Support Request" link above these online forums in the gray bar and create a new request and ask them.

If your process cannot tolerate these failed DIs, consider converting the 230VAC signals to 24VDC signals using (opto-isolated) voltage converters.  That's just my years of experience speaking when I know no matter how good the power is, there will be times when unexpected things happen to the AC bus, or when large ~230VAC loads go offline and kick-back on the 230VAC supply, temporarily raising the 230 VAC supply - often well above spec.

I also know from many years using S7-1200/1500 devices, the 24VDC inputs have the most robust protections built in and I rarely experience problems even when the inputs exceed the specs by a good margin.

M_Sultan

We are experiencing a recurring issue with the DI 16x230VAC 6ES7521-1FH00-0AA0 channels in some of our remote I/Os in the field. These channels are frequently getting damaged.

When a channel is damaged, it exhibits flickering behavior, turning on and off at a high frequency. Upon checking the current, I found that the damaged channels are drawing less than 4 mA, while functioning channels should show a current greater than 10 mA.

What could be causing this issue, and how can we protect the channels to prevent further damage?

 

Thank you for your response.

We have confirmed that the voltage in the 460V supply drops by approximately 12% to around 405V when starting large motors. This supply feeds the transformer (460/230V) to the PLC input channels of the MCCs.

According to the datasheet of the input card, the voltage range is as follows:

• For signal “0”: 0 to 40 V AC
• For signal “1”: 79 to 264 V AC

Please refer to the attached screenshot from the manual (page 18) for more details.

As in the mansion range in manual, why did the channels damage if within the voltage range?