CHANGE OF RESISTANCE TEST STAND – P13472

CHANGE OF RESISTANCE TEST STAND – P13472

Mission Statement: To design a test stand capable of measuring the temperature of an H.I.D. Magnetic Ballast using a linear regression of the transient decay of ballast coil resistance for up to 6 ballast coils. The test stand is to be mobile, user-friendly, interfaced with Labview, and capable of performing manual and automatic ballast temperature measurement tests. The resistance measurements taken must be 4-wire resistance measurements that adhere to the UL844 H.I.D. Magnetic Ballast standards.

Company Sponsor: The company Cooper Crouse-Hinds from Syracuse, NY established the test stand as an endeavor to replace a charming piece of rapidly aging laboratory equipment that Cooper currently has in-house.

Faculty Mentor: Professor Benjamin Varela, Department of Mechanical Engineering

Team Members: Jacob Lennox, Department of Mechanical Engineering (right) Colin Payne-Rogers, Department of Mechanical Engineering (left)

Concept: Test stand mobility will be achieved by packaging all of the hardware on a cart. The test stand system contains three units: a Dell Latitude E5430 (laptop), a custom relay box and a National Instruments PXI Chassis. The laptop, sporting Windows 7, allows the user to control the relay box and PXI system via a Labview graphical user interface. The Labview program design is meant to be easy-to-use for the trained Cooper technicians. Its interface contains all of the controls and indicators needed for the technician to run manual tests, run automatic tests and obtain ballast coil temperature measurements. The PXI system, a PCI expansion module that contains two switches and one multimeter, controls switching between the 6 coils whose resistance is being measured and then takes the resistance measurement of each coil. The multimeter is capable of taking 4-wire resistance measurements at a resolution of 0.01 Ohms. The relay box acts as a signal routing hub, connecting the ballast wires to the multimeter in such a way as to allow all of the coil temperatures to be measured. It also contains two relay circuits that connect and disconnect the power and resistance-measurement circuits of the ballast accordingly (controlled by Labview). The relay circuits consist of 4-pole single-throw switches, allowing only the power circuit to be active while the ballast is operating and only the measurement circuit to be active while the National Instruments hardware is switching between coils and taking resistance measurements. This is done to prevent damage to the measurement hardware for ballast that operate in the 120 VAC to 600 VAC range.

Proof of Concept: An experiment was designed to show that staging the resistance-measurement and power circuits with relays is a valid method of dissipating the ballast’s stored energy prior to measuring the resistance of the ballast coils. To the right is a conceptual design and experimental setup. The results of the experiment compared well with known Cooper results. 120 VAC was used to power the ballast and to control eight SPST relays. Relays CR1 and CR2 separated the ballast supply voltage from the ballast itself and were controlled by a manual switch S2. Relays CR3-CR8 separated the resistance measurement leads from the multimeter and were controlled by a manual switch S1. Two transformers were used to convert the 120 VAC to a 24 VDC control voltage. The results of the experiment showed that a set of relays (CR3-CR8) could be used to separate the multimeter from the ballast supply voltage while another set of relays (CR1, CR2) allowed the ballast supply voltage to power the ballast. The roles of these relays was reversed while resistance measurements were taken.

Final Design: The five pictures to the left detail the relay box and PXI chassis used in the final design. Top left and bottom left are front and back images of the overall system. From top to bottom on the right the ballast wire connections are shown: the connection of ballast wires to the relay box, the power and resistance-measurement relay circuits, a conversion terminal block that reduces wire gage and splits each ballast resistance lead into two leads (for 4-wire measurement) and the connection of all resistance leads to the National Instruments PXI chassis for coil switching and data acquisition.