Siemens VFD troubleshooting starts with checking the electric motor and VFD terminal connections. Motor and VFD connections can be overlooked, loose, or, wired to the incorrect terminals; so, checking all connections is suggestedbefore pulling the VFD and sending it in for a repair evaluation.
Heat cycles and mechanical vibration can lead to sub-standard connections. Reusing torque screws is not a good idea, and further tightening an already tight connection can ruin the connection. Bad connections eventually lead to arcing. Arcing at the drive input terminal can result in nuisance, over-voltage faults that may clear input fuses, or damage protective components. Arcing at the VFD input or output terminals may result in over-current faults or damage to the power components. Loose connections can cause erratic operation. For example, a loose START/STOP signal wire to the drive can cause uncontrollablestarting and stopping. A loose speed reference wire can cause the drive speed to fluctuate, resulting in scrap, machine damage, and personnel injury.
Siemens VFD Troubleshooting Diode and IGBT
Prior to applying power during the Siemens VFD troubleshooting process, the input and output power sections need to be tested. If there is a short on the input side or output side of the VFD, further damage can be caused to the unit if power is applied to it. For this reason, special meters should be used to properly test the input and output power sections of the drive, prior to applying power to the Siemens VFD unit. If a short is found, the VFD can be disassembled and the cause of the short can be diagnosed and quoted for repair. If the Siemens VFD repair is too costly, VFD replacement and availability is considered.
Siemens VFD Troubleshooting and Power Up
If the input and output power sections test healthy during the Siemens VFD troubleshooting process, power is applied to the VFD unit to perform amp reading and output frequency testing. Slowly increasing the power voltage during this step of the Siemens VFD troubleshooting process is suggested to gather accurate meter readings and to protect the motor. The power voltage is slowly increased on the Siemens VFD until the rated input voltage of the drive is reached. Depending on whether or not the Siemens VFD provides a display will determine what further action will be taken. If display is unavailable, disassembly and diagnosis of the internal power supply of the control section of the drive is necessary to further evaluate cause of failure and establish cost and lead time for the Siemens VFD repair.
Siemens VFD Troubleshooting With Motor
If the previous tests have passed during the Siemens VFD troubleshooting process, a basic JOG / RUN function of the drive can be performed with a simple template program. When a Siemens VFD comes into our facility, repair techs will backup all existing programs stored in the drive prior to installing a test template program for this test run procedure. Backing up the Siemens VFD program ensures availability of the program for installation, once the repair is complete. The best method for backing up Siemens VFD programs will depend on the series and model of drive. After the VFD programs have been backed up, the Siemens VFD is reset to factory defaults through the keypad. Once the Siemens VFD is reset to factory default settings, a basic START / STOP is recommissioned of the VFD connected to its motor. Closed loop testing will be necessary when an encoder is involved. If the motor will not run, the output voltages and motor current ratings are tested to verify that the drive is functioning properly for motor rotation.
Siemens VFD Troubleshooting and Routine Maintenance
Siemens VFD troubleshooting should be performed by trained electrical technicians during regular routine maintenance. Routine maintenance prevents Siemens VFD failure and production loss due to machinery downtime. Siemens VFD repair cost and lead times can also be reduced with routine maintenance. Siemens VFD repair can be expensive depending on board and component damage which ultimately will cost manufacturers production downtime during the repair process. Most manufacturers keep spare Siemens VFD units in stock to prevent production downtime during the Siemens VFD repair.
Siemens VFD Troubleshooting and Safety
Siemens VFD troubleshooting and Siemens VFD repair should be taken with extreme caution and only be performed by technicians who have training and experience in working with electrical equipment. Precision Electric strongly recommends consulting an expert in the field when repairing all industrial electrical equipment. Many drives have an internal DC bus that retains a charge after power has been cut to the drive, and as a result, it does not mean that it’s safe to work with. Technicians working with Siemens VFD units and other related equipment must always take extra precautions to ensure proper safety measures are taken, or injury or even death may occur.
Siemens VFD Troubleshooting and Repairs
Most companies who offer Siemens VFD troubleshooting and Siemens VFD repair do not even perform these services themselves. These companies outsource the repair to a third party certified VFD Repair Center, such as Precision Electric. Precision Electric receives Siemens VFD repair jobs everyday from companies who offer VFD repair. Those third party repair companies then mark up the repair cost to their customers. Manufacturers are encouraged to ensure that their Siemens VFD Repair is being performed at the actual site of whoever is offering the service.