Hello everyone, I am looking to create a system that can control multiple AC contactors and disable them for a set amount of time when a specified current threshold is exceeded across all three phases of an incoming power supply. I will need a large quantity of these systems, so cost-effectiveness is crucial. My plan is to utilize 5A CTs on the power cables (x3) and integrate them with a Programmable Logic Controller (PLC) to monitor the current values. I am currently facing challenges in determining the most efficient approach to achieve this, taking into consideration the limitations of the M221 PLC, which has 2 analogue inputs (0-10V). I am also exploring the option of utilizing cost-effective CTs and converting the 5A analogue signals to either 0-10V (requiring an additional PLC module), 4-20mA (needing an expansion board), or digital format. I am seeking recommendations on the optimal hardware setup for this task, particularly in converting the 5A signals to digital format across all three phases as cost-effectively as possible. Any suggestions or guidance on this matter would be greatly appreciated.
If you are referring to a digital switch that activates at a specific AC current level, consider using a Dwyer current switch for this purpose. Additionally, there are converters available to transform a 0-5A AC output from a current transformer into a DC signal. Visit the following links for more information: Dwyer current switch (https://www.lesman.com/mcs-111050) and AC current converter (https://www.datexel.com/ac-current-converter-dat5023iac-a.html) and guidance on converting CT signals to standard 4-20 mA output (https://www.nktechnologies.com/engineering-resources/converting-ct-signal-standard-4-20-ma-output/).
I have effectively measured AC current using Veris instruments, such as their current monitoring tools found at https://www.veris.com/126822/category/current-monitoring. Another useful product from Veris is their H608 current switch, available at https://www.veris.com/995242/product/veris-h608-current-switch.
If I'm not mistaken, it could be beneficial for you to explore bulk pricing options for a smart energy meter for this specific scenario. Consider purchasing one that includes built-in current transformers (CTs) for maximum efficiency.
Simon Gallagher mentioned that he is having trouble finding cost-effective 5A to digital converters for 3 phases. He noted that using setpoint relays for digital inputs may be a more affordable option compared to analog IO or current transmitters with communication features. Monitoring all three phases of each motor may be excessive if the goal is just to measure motor load in regular operation rather than detecting phase to phase current imbalances.
In his post, simongallagher proposed a challenge of developing a system to control AC contactors, activating a 'lockout' feature when a specific current level is exceeded in a three-phase power supply. With a potential requirement for hundreds of these systems, cost-effectiveness is a key factor. The plan includes using 5A CTs on electrical cables and integrating them with a PLC to monitor the values. However, the dilemma lies in finding the most efficient method given the limitations of the M221 PLC's two 0-10V analogue inputs. The options considered are converting the 5A signal to 0-10V (requiring an additional PLC module), 4-20mA (needing an expansion board), or digital. The search for cost-effective 5A to digital converters for three phases has proven challenging. For advice on the optimal hardware configuration, suggestions have been made to explore options like those available at https://www.phenixcontrols.com/Current_Sensor/Three_Phase/. Your input on this matter would be greatly appreciated.
From your description, it seems you're looking for a capacity to monitor three-phase power supply and control AC contactors based on the set threshold. Considering the M221 PLC's limitations, I suggest exploring Arduino as a possible alternative. With its open-source platform, cost-effectiveness, flexibility and the ability to take analog and digital inputs, Arduino can handle the CT outputs directly. A small adjustment might be required to convert 5A to a voltage level that Arduino can read (0-5V). This can be achieved by employing a burden resistor in the circuit. And for converting the 5A analogue signals to digital, you can easily program a microcontroller like the Arduino to do this A/D conversion, eliminating the necessity for an additional PLC module or expansion board. Furthermore, there are plenty of libraries available for Arduino to calculate actual current from the CTs and control the contactors accordingly. All these combined could significantly reduce your overall system cost. For any additional protection, Arduino can also interface with solid-state relays, circuit breakers, etc. as per your safety requirements. You might want to explore these options a bit.
It sounds like you're undertaking quite the project. Many engineers often leverage Arduino with current sensors like the ACS712, which can read the intensity of the AC or DC current and pass it onto the Arduino as an analog value depending on the intensity. Arduino UNOs are also quite cheap, and when paired with a good current sensor, it could represent a cost-effective solution. For the signal conversion, digital converters like the ADC 0804 Chip could be used to convert the analogue signal from the CT into a digital one for PLC. However, with everything, I would encourage testing with a few before fully committing to ensure your needs are met. Good luck!
Hi there! It sounds like you're on the right track with your project. Since you're looking for cost-effectiveness, consider using a multi-channel current transducer that outputs directly to a digital protocol like Modbus or RS485. This way, you can connect multiple CTs directly to your PLC without needing extra modules for signal conversion. Alternatively, if you stay with the 0-10V solution, you might explore using an I/O module that can handle multiple analog inputs—there are some budget-friendly options out there that could fit well with your M221 setup. Also, think about whether you can group the phases logically for monitoring; if you're able to use one CT for two phases under certain conditions, that could save you on costs too!
It sounds like you’re on the right track with utilizing CTs and a PLC for monitoring, but I recommend considering using a small microcontroller, like an Arduino or Raspberry Pi, as they can handle multiple inputs and are often more cost-effective for scaling production. You could find low-cost ADCs to convert the 5A signals directly to digital format, enabling you to manage all three phases without needing extensive additional gear. Alternatively, if you stick with the M221, you might explore using signal multiplexers to switch between different CTs for the limited analogue inputs. Just be sure to factor in the reliability and ease of integration, as that can save you headaches down the line!
Hey! It sounds like you have an interesting project on your hands. Since you're aiming for a cost-effective solution, you might want to consider using low-cost digital current sensors with integrated communication features—like Modbus RTU or MQTT—which can directly connect to your PLC. Instead of converting 5A analogue signals, these sensors can provide digital outputs that would streamline your setup and possibly save on additional circuitry. Also, look into using a Raspberry Pi or Arduino in conjunction with your PLC to handle additional logic or processing if needed. This could give you more flexibility while keeping costs down! Good luck with your project!
✅ Work Order Management
✅ Asset Tracking
✅ Preventive Maintenance
✅ Inspection Report
We have received your information. We will share Schedule Demo details on your Mail Id.
Answer: - To monitor current across multiple AC contactors and control them with a PLC, you can use current transformers (CTs) on the power cables to measure current values. These values can be integrated with a Programmable Logic Controller (PLC) to monitor and control the contactors based on set thresholds.
Answer: - The main challenge of using an M221 PLC with limited analogue inputs for current monitoring is finding an efficient approach to convert the 5A CT signals to a format compatible with the PLC's inputs. Options include converting the signals to 0-10V, 4-20mA, or digital format using additional modules or expansion boards.
Answer: - To convert 5A analogue signals from CTs to digital format cost-effectively, you may consider using cost-effective CTs and converting the signals to digital format through appropriate modules or expansion boards. It's essential to choose a hardware setup that efficiently converts the signals while keeping costs in check.
Answer: - For optimal hardware setup to convert 5A CT signals to digital format for current
Join hundreds of satisfied customers who have transformed their maintenance processes.
Sign up today and start optimizing your workflow.