200kVA Frequency Converter Nuisance Tripping

We have an HZ-50-33200 200kVA frequency converter. When we did the calculation for the load we needed we oversized the unit to the 200kVA unit to plenty of current for motor starting. When we are running the plant with full load we are close to 50 amps.  We can start the largest motor and have the current jump up to 90 amps then come back down without the unit tripping. We have noticed that once in a while when the load on the largest motor fluctuates we have a trip on the unit which causes the converter to shut down.
What could be causing this, is there some adjustment we can make so that we don’t have this shut down the converter?

It sounds like your 200kVA frequency converter is experiencing nuisance trips due to load fluctuations. These converters often have protective settings that might be a bit too sensitive for your application. Check the settings for overcurrent protection, voltage dips, and transient response. Sometimes, tweaking these settings can help accommodate the brief surges without tripping the unit.

Jasper wrote:
Hi, Jasper, regarding the converter trips when the load on the max motor fluctuates, we think it's due to an inrush current from running the motor at full load.
The solution now is that you can try to adjust the current protection threshold of the converter, please try to adjust the potentiometer of the 3-phase motherboard counterclockwise 8 turns and test again.
In addition, you can minimize the maximum motor full load or overload operation, and lower the system current threshold.

We adjusted the potentiometer on the motherboard controller 8 turns counterclockwise. That seemed to help with the nuisance tripping of the converter when the large motor was starting. We are still getting some nuisance trips when all of the motors are running and have been running for some time. I am wondering if you have any ideas of what might be causing that.
I am looking into grounds going out to each piece of equipment. One thing I noticed is the equipment is mounted in 3 different shipping containers and each container has a separate power feed going into it. Each power feed has a separate ground going to each container, but I am not sure if each container is grounded together. Maybe the grounding could be causing some imbalance that affects the frequency converter.
Any other ideas that might cause some extra noise or would cause the converter to trip?

Jasper wrote:
The converter adjusting potentiometer 8 circles helped a bit.
When all the motors are running for some time, the tripping fault will still occur. We think this may be caused by the overload of the motor (the current increases instantaneously), which has nothing to do with the separate grounding of the container.
1. Could you please check all your motors for occasional overloads during operation?
2. Could you provide us with the power, voltage, current, and other parameters of all motors in your system for confirmation? We need to confirm the specifications of each motor.

Jasper wrote:
It's good to hear that adjusting the potentiometer helped with the startup tripping issue. Regarding the ongoing nuisance trips, your suspicion about grounding might be valid. Ensuring that all containers are properly bonded together with a common ground is crucial. Differences in potential between grounds can create circulating currents or ground loops, leading to instability and tripping in sensitive equipment like frequency converters.

Danie wrote:
You are right. Ground loops can indeed cause a lot of problems. Check that each container is bonded to a single ground point. Additionally, ensure that all ground connections are clean and secure. Loose or corroded ground connections can introduce resistance and noise into the system.

I think we found out what the problem was causing the nuisance tripping.
There is one larger motor that is 25HP (18.5 KW) at 400VAC, 3 phase. This motor has two rolls that can be adjusted for grinding products, we think that some operators have been adjusting the gap between rolls which is causing the spike in current like an overload condition that is causing the problem with the frequency converter.
I did have one new thing happen and I am hoping there is an easy answer. I have attached two pictures below one that shows what the display usually shows 50 HZ, 228.3 (Ratio number to get 400V output voltage). Today when we were looking at the display we noticed the frequency was showing 160.4 Hz, 227.6 V. We tried to adjust the frequency number back to 50 Hz but it won’t let us go below 100 Hz. If we set the frequency adjust dials to 000.0 Hz the display shows 100, if we set it to 50.0 Hz the display shows 150.0 Frequency.
Could there be something wrong with the one display digit? Is there some way to reset this?

Jasper wrote:
If the frequency can't be set properly, the feedback capacitor of the converter or the motherboard may be also affected by the spike current/voltage.
To troubleshoot, you first measure all feedback capacitors (normal capacitance should be 75-80uf) according to our requirements, and feedback on the measurement results to us. As shown in the attached pictures where the capacitors are located, you can follow the attached troubleshooting instructions to measure these capacitors and then we will provide the next step solution.

ATO wrote:
These are the values I measured for all capacitors and a photo of one of the tests.

Jasper wrote:
These capacitors are normal and may still be a problem with the motherboard. You can replace the V-phase motherboard and frequency line.
Note: For safety, before you use new spare parts and install the new motherboard, please first disconnect the input power of the converter, stop it for more than 30 minutes, and then install the spare parts after the capacitor is discharged.