Coil Suppression
Start Date
15-4-2021 9:30 AM
End Date
15-4-2021 9:45 AM
Student's Major
Automotive and Manufacturing Engineering Technology
Student's College
Science, Engineering and Technology
Mentor's Name
Matthew Simones
Mentor's Department
Automotive and Manufacturing Engineering Technology
Mentor's College
Science, Engineering and Technology
Description
Relay coil suppression aims to reduce/eliminate the back EMF or voltage spike induced upon the collapse of the magnetic field. This research in particular looks at the back EMF generated by a 12-volt relay that could be used in the Formula SAE Electric (EFSAE) design competition, where relays are often controlled by a low voltage battery management system and are susceptible to damage. Coil suppression in these tests utilizes diodes of different types and sizes. The EFSAE team utilizes off the shelf relays, which are available with or without internal coil suppression. Choices can be limited when looking for relays with coil suppression and are also more expensive. Designing an external coil suppression circuit could save $20 per relay for a total savings of $160 per year for the team, and a more complete understanding of the danger of a non-suppressed relay would be understood. To test the benefits of coil suppression a simple circuit was made where the test item was placed in parallel with the relay and cycled on and off using a toggle switch. Using an oscilloscope, the voltage with and without suppression was measured with readings of 13 volts and 280 volts, respectively. Test results show that diodes costing less than a dollar are effective in mitigating the transient response from the relay to within safe voltage levels. These results will guide the EFSAE team in the design and selection of an appropriate diode for external coil suppression and will allow the team to utilize relays that may not be offered with an internal coil suppression option.
Coil Suppression
Relay coil suppression aims to reduce/eliminate the back EMF or voltage spike induced upon the collapse of the magnetic field. This research in particular looks at the back EMF generated by a 12-volt relay that could be used in the Formula SAE Electric (EFSAE) design competition, where relays are often controlled by a low voltage battery management system and are susceptible to damage. Coil suppression in these tests utilizes diodes of different types and sizes. The EFSAE team utilizes off the shelf relays, which are available with or without internal coil suppression. Choices can be limited when looking for relays with coil suppression and are also more expensive. Designing an external coil suppression circuit could save $20 per relay for a total savings of $160 per year for the team, and a more complete understanding of the danger of a non-suppressed relay would be understood. To test the benefits of coil suppression a simple circuit was made where the test item was placed in parallel with the relay and cycled on and off using a toggle switch. Using an oscilloscope, the voltage with and without suppression was measured with readings of 13 volts and 280 volts, respectively. Test results show that diodes costing less than a dollar are effective in mitigating the transient response from the relay to within safe voltage levels. These results will guide the EFSAE team in the design and selection of an appropriate diode for external coil suppression and will allow the team to utilize relays that may not be offered with an internal coil suppression option.
