Electrical wiring on-site installation and commissioning methods
Most of the time, we repair electric motors. We don't handle the installation of motors, the laying of wiring, or the installation and commissioning of control cabinets. However, "skills are never a burden," so today we'll recommend "on-site installation and commissioning methods for electrical circuits." We hope that every electric motor repairman can improve their skills and provide value-added services to users.
I. On-site installation and wiring of electrical circuits
First, we need to understand whether the wiring is done via buried conduits or cable trays. Based on the engineer's electrical wiring diagram, locate the endpoints of each device's wiring and check if the buried conduit locations correspond to the endpoints of each device's wiring.
Second, fix the electrical cabinet to the on-site base. If there are multiple cabinets, they need to be connected together. Install busbars and fix the on-site control panel.
Third, for primary circuit wiring, it's best to run cables of the same specification together. Common electrical wiring practices often involve starting from the head of the equipment and laying all cables together. This results in multiple rolls of cable being unrolled simultaneously, and several rolls need to be moved around every time a location is changed, easily leading to tangling. My suggestion is to unroll a roll of cable of a specific specification, and then run that cable from the beginning of the entire equipment system to the end, covering all appliances requiring the same specification, such as motors and fans of the same specification. We can run these cables first, then check to ensure nothing is missing, and mark that group of cables of the same specification on the cable layout diagram. Next, we run the next group of cables of the same specification, marking them in the same way. This way, we only need to unroll one specification of cable at a time, and after all the wiring for a single cable is completed, any remaining cables of that specification can be stored and labeled for identification.
Fourth, clarify the wiring sequence. On-site wiring should ideally proceed as follows: first large wires, then small wires; first primary wires, then secondary wires; first motor wires, then other load wires. Label each wire after it is laid. The advantage of laying large wires first is that they won't press down on small wires in the cable trench or tray. The advantage of laying primary wires first, then secondary wires, is that there are relatively fewer primary wires, allowing for faster completion of the main circuit, and it also facilitates interference handling for secondary wires.
We begin with the motor wiring, followed by the following wiring in sequence: motor and fan wiring, heating resistance wire wiring, control circuit button operation point wiring, hydraulic circuit wiring, analog signal wiring such as temperature sensor wiring, encoder wiring, and communication line wiring. By addressing the main circuit first and then the control circuit's switching signal wiring, we can find wiring solutions for the subsequent lines that are prone to interference, thus avoiding interference problems during the wiring stage.
Fifth, regarding wiring, first, record which color or number corresponds to which terminal for each cable. Record each cable as it is connected, and it's best to maintain consistency for cables of the same specification. For example, all motor wires should ideally be yellow, green, and red, corresponding to UVW. All primary cables and loads should be connected after the primary wiring is completed, and then secondary wiring should proceed. This avoids confusion, especially when there are many cables on site. It also keeps the site clean and tidy, unlike the messy situation where all the cables are laid out and then exposed. Furthermore, wiring and connecting in stages allows the installation project to progress systematically, rather than being done haphazardly.
II. Debugging Methods for Electrical Circuits
Once the wiring is complete, we need to test the wiring to ensure there are no errors.
First, we need to check for incorrect cable connections. Do not connect the cable for motor A to motor B, or the cable for fan A to fan B, especially lines running through the same conduit. Ensure all control lines use the same cable. Check that the color or number of each terminal on the electrical cabinet terminal block corresponds correctly to the operating point on site. For example, if a button corresponds to a yellow wire, but is connected to a green wire on the electrical cabinet terminal, these details must be carefully checked. Also, check for short circuits between motor phases, short circuits to the motor housing, and open circuits. Verify that the wiring of buttons and indicator lights matches the terminal block wiring, etc.
Secondly, the circuits should be tested one at a time, cabinet by cabinet. For example, in the first cabinet containing all motor circuits, we can turn on the switch, briefly activate the contactor, and observe if the motors reverse direction. If they do, correct them immediately. Then test the second cabinet, such as the fan circuit, briefly activating the contactor to observe if the fan reverses direction.
Third, test the signals of all buttons. Many control systems now connect buttons to a PLC. One person can press each button on-site, while another person observes the corresponding input indicator light on the PLC. If the light doesn't illuminate, investigate the cause. Resolve the problem to ensure all button signals are normal and the button indicator lights are lit.
Fourth, debug the feedback signals of all main circuits. For example, for all the motors in the first electrical cabinet, we can jog the contactors one by one to check if the signal is fed back to the PLC. If not, check the wiring. Observe whether the sampling signal is sampled. For example, for the ammeter connected to the current transformer, use a screwdriver to hold the contactor and observe whether the ammeter indicates current.
Fifth, manually run the frequency converter and DC speed controller to check for problems with the motor, abnormal noises from the reducer, and feedback from the motor encoder. For example, we were debugging a 590 DC speed controller. We made a simple push-button box with two selector switches—one for starting and one for enabling—and a potentiometer to provide a 0-10V signal. We connected this push-button box to the speed controller, and then we could test the motor's operation and see the encoder feedback signal on the 590. For instance, when we tried to adjust the speed of a certain DC motor, it immediately reported an error. This was because the encoder feedback direction was opposite to the actual direction of the motor, even though the motor direction was correct. So, we reversed the A and B phase signals of the encoder, and it worked normally.
Sixth, check whether the signal sources of all other feedback signals can normally feed the signal back to the PLC. For example, for an electrical appliance, we use a current transformer to sample the current signal to trigger an intermediate relay, and use the normally open signal of the intermediate relay to feed back the appliance's operation to the PLC. We can then use a screw to hold the contactor of this appliance energized and observe whether the corresponding input indicator light on the PLC is lit to ensure that the feedback signal is correct. Another example is a position sensor in the field that feeds different resistance values as the position moves. We can move the sensor to that position and have someone measure the resistance value at the other end of the electrical cabinet wiring to see if it changes normally, ensuring that the resistance signal is fed back correctly and eliminating feedback errors caused by wiring problems.
At this point, we can basically eliminate all the wiring problems and proceed to the next step of PLC program debugging and overall equipment linkage debugging.
In summary, the installation process involves laying the primary wiring first, followed by the secondary wiring. After laying one type of cable, the copper lugs should be properly installed and connected, completing each stage one by one. During debugging, first check the wiring for safety, then adjust the motor direction, and finally ensure that manual operation is normal and that signals are being fed back to the PLC or other controllers. Proceed step by step, think clearly, identify and solve problems, and improve your work skills. I hope this is helpful.
