SuPER Cart DC Motor Model. And. Ultra-Capacitor Addition. Joseph Witts

Transcription

1 SuPER Cart DC Motor Model And Ultra-Capacitor Addition Joseph Witts

2 DC Motor Model DC Motor Testing In order to develop a model of the entire SuPER cart for simulation purposes, a model of the DC motor had to be developed. The first task was to contact the manufacture in order to obtain as much information about the motor as possible. A Dayton 6MK98 1V ¼ hp motor was purchased from Grainger. However, Dayton is not really a company but just a name that Grainger places on motors they sell. The real manufacture is Leeson, and the Leeson part number for the motor is The following parameters were obtained from Leeson. This information was obtained over the phone, because Leeson will not give written parameter values to the public. These values were used as a starting point for developing a model that matches the DC motor. Motor 5 o C Back EMF Constant: 6.64 V/kRPM Motor Torque Constant:.56 lbs-in/a Rotational Inertia: 3.1 lb*in Armature Inductance:.33mH Stall Torque: A In order to properly model the DC motor, experimental data was required to determine how the motor reacted during start up conditions under load. So testing was conducted to determine how much current the DC motor was drawing during start up. This was tricky because there was no available equipment that could plot the current as a function of time. Since the test setup included only the battery and DC motor, the battery s voltage drop during the start up of the motor was used to determine how much current the battery was supplying to the motor. This was accomplished by first determining the internal resistance of the battery, and then using the change in voltage of the battery to calculate the current supplied. The assumption that the battery s internal resistance remains constant during motor start up was made, so the accuracy of the calculated data depends on how much the battery s resistance changes. To determine the internal resistance of the battery the open circuit voltage of the battery was measured, and a shunt was placed in series with the motor to determine the current flowing in the circuit (Schematic 1). Internal Resistance + Battery V Battery Terminal Voltage _ Shunt DC Motor Schematic 1: Circuit used to determine the battery s internal resistance

3 Next the motor was turned on with a 1.6 lbs-in load. The steady state battery terminal voltage and shunt voltage was measured and the battery s internal resistance was calculated as follows. Open circuit battery voltage = Voc = V Steady state battery terminal voltage = Vss = 1.5 V Shunt voltage = 15.5 mv 3A A Shunt Ratio = =.6 5mV mv A Shunt current = I =.6 ( 15.5mV ) = 9. 3A mv Voc Vss 11.75V 1.5V Battery s Internal Resistance = R Bat = = =. 19Ω I 9.3A Now that the battery s internal resistance is known. The current supplied by the battery can be calculated using the following formula: Voc V ( t) I( t) = R Bat Where V(t) values were taken from the oscilloscope trace of Plot 1. The voltage values and calculated current values during the motor s starting in-rush can be seen in Data Table 1. Plot 1: Battery terminal voltage trace with DC motor loaded at 8 in-lbs

4 Time (ms) Voltage (V) Current (A) Time (ms) Voltage (V) Current (A) Data Table 1: Measured battery terminal voltage obtained from oscilloscope and calculated current DC Motor Modeling A PSpice model (Schematic ) of a permanent magnet DC motor was found at where the author modeled the mechanical side of the motor with an electrical equivalent. Mechanical torque was represented by voltage, speed by current, and drag by a resistor.

5 Schematic : DC motor model found online After looking at the mechanical side of this model it became apparent that it can only be accurate for one value of torque. Schematic 3 is a simplified version of the mechanical side of the model. Once the motor reaches steady state operation the inertia can be ignored, so the speed is determined by torque and viscous drag (R). If the value of R is determined from the steady state values of Data Table 1, and the same value of R is used for rated torque the error is large as seen below. Inertia 1 Torque R Viscous Drag Schematic 3: Simplified mechanical side of the DC motor model Using measured values from Data Table 1 to calculate R: At steady state inertia does not need to be considered. Torque = ( Speed )( Viscous _ Drag) Torque 8lb in lb in R = = = Speed 1.7kRPM krpm

6 Using this value of R to calculate speed at rated torque: Torque 8.75lb in Speed = = = 1. 11kRPM Viscous _ Drag 7.944( lb in ) krpm Error of the DC motor s calculated speed using this value of R for rated speed: Error = 1.8 1% = 38.8% So this model of a DC motor is missing some component that can yield more reliable results. I came across a document online for testing and modeling a DC motor at that showed there was another component of drag that needs to be considered when modeling a motor. Coulomb drag, unlike viscous drag, is not a function of speed and is constant. So the coulomb drag was modeled as a DC voltage source opposing the applied torque voltage source of Schematic 4. To solve for the appropriate value of viscous and coulomb drag two equations with two unknowns needed to be developed. By using the steady state values in Data Table 1 and the motor s rated values the two equations were developed. Below are the calculations used to determine the values of coulomb drag (X) and viscous drag (R) to be used in Schematic 4. Coulomb Drag Inertia 1 X Torque R Viscous Drag Schematic 4: Variables used to determine both viscous and coulomb drag At steady state inertia does not need to be considered. ( Speed )(R Torque = X + ) From measured values of Data Table 1 Torque = 8lb in Speed = 1.7kRPM Equation 1 ( 8 lb in) = X + ( 1. 7kRPM )(R ) DC motor s rated values Torque = 8.75lb in Speed = 1.8kRPM Equation 8.75lb in = X kRPM ( ) ( )( R)

7 Equation 3, solving for X in Equation X 8.75lb in 1. 8kRPM = ( ) ( )( R) Substitute Equation 3 into Equation 1 ( 8 lb in) = ( 8.75lb in) ( 1.8kRPM )( R) + ( 1. 7kRPM )( R).75lb in R = = kRPM ( lb in ) krpm Substitute R into Equation 1 and solve for X ( 8 lb in) = X + ( 1.7kRPM ) X = 7. 48lb in lb in krpm Now that the values of viscous and coulomb drag have been determined, the rest of the DC motor s model parameters can be found. The DC motor model has an electrical side and a mechanical side represented by electrical components. The electrical side uses an inductor to represent the motor s armature inductance, a resistor for the armature resistance, and a current controlled voltage source to represent the back emf. The mechanical side uses a current controlled voltage source to represent the applied torque, a DC source for coulomb drag, an inductor for inertia, and a resistor for viscous drag. All of these parameters, except the two drags, where solved by trial and error by comparing the simulations output to the data gathered in Data Table 1. The manufactures supplied values were used for the initial motor parameters and adjusted until the simulated current waveform Plot 5 represented the actual current waveform Plot 4. See Schematic 5 for the final DC motor model circuit and parameters.

8 R_Battery 1 V_Battery 11.75V.19 L_Motor.7m R_Motor.16 Back_EMF Km= Torque Kt= Coulomb_Drag Inertia 1. Viscous_Drag.9458 Schematic 5: Final PSpice DC Motor Model Notice that the magnitude of the armature inductance and resistance is noticeably greater than the manufacturer s values. This is because the testing setup measured the voltage across the battery s terminals not the direct input to the motor. So the resistance and inductance of the wire going from the battery to the motor s plug, and the 16 foot long cord for plugging in the motor, are added to the armatures inductance and resistance. To improve this model the voltage needs to be measured at the battery terminal and the input to the 16 foot long plug for the motor. This way the wire connecting the battery to the plug can be modeled separately, so the final motor model will represent only the motor and the 16 foot cord connected to the motor. The following plots below can be used to tell how well the model reflects the actual data by comparing the actual waveform of the current and voltage during the motor s in-rush stage to the simulation. As you can see by comparing Plot and Plot 3 the voltage sags are reasonably similar, and the current spike of Plot 4 and Plot 5 are also very similar. There is still room for improving the model by not lumping the impedance of the wire going from the battery to the plug and the 16 foot cord with the DC motor s armature inductance and resistance. Since this is just the initial prototype phase of the project, and the wiring will likely change, further refinement of the model was not conducted. Plots 6 and 7 were included to show how the modeled DC motor s applied torque and speed change as a function of time, and how the steady state values are very close to those in Data Table 1.

9 Battery Terminal Voltage During DC Motor In-Rush Mechanical Load = 8 in-lbs Voltage (V) Time (ms) Plot : Plot of the actual battery terminal voltage from Data Table 1 1V 1V 8V 6V s.1s.s.3s.4s.5s.6s.7s.8s.9s 1.s V(L_Motor:1) Time Plot 3: Modeled DC motor s battery terminal voltage

10 DC Motor In-Rush Current Mechanical Load = 8 in-lbs Current (A) Time (ms) Plot 4: Plot of the actual motor in-rush current from Data Table 1 4A 3A A 1A A s.1s.s.3s.4s.5s.6s.7s.8s.9s 1.s I(R_Battery) Time Plot 5: Modeled DC motor s in-rush current draw

11 16V 1V 8V 4V V s.1s.s.3s.4s.5s.6s.7s.8s.9s 1.s V(Torque:3) Time Plot 6: Modeled DC motor s torque in lb-in 1.A.5A A s.1s.s.3s.4s.5s.6s.7s.8s.9s 1.s I(Coulomb_Drag) Time Plot 7: Modeled DC motor s speed in krpm Next the model was used to compare simulated values to actual data found on the wiki (files dc_motor and dc_motor_solar) and the motor s rated values. As you can see from Data Table the simulated values are reasonably close to the actual data. One discrepancy is with the dc_motor file simulation where the simulated speed is 1% less than the actual data. I m not sure how the data was gathered for the dc_motor file, but if the recorded voltage is actually the motor voltage instead of the battery voltage this could account for the larger error. If this is true the simulation should have a slightly higher battery voltage, which will increase the simulated torque and speed slightly and decrease the error. As far as the.4% error for the motor operating at rated values, the error is likely due to the fact that the model has impedance of the wire going from the battery to the plug and the 16 foot cord, lumped together with the motor s armature inductance and resistance. Even though the battery voltage is V the actual voltage at the input of the motor (manufacture s rated voltage location) is lower. So the real

12 percent difference is lower than %, due to the voltage drop across the wire going from the battery to the plug and 16 foot cord. Condition Battery Voltage (V) Torque (lb-in) Speed (rpm) Motor Current (A) Data Table Simulation Percent Difference.% -.% -1.9% -.5% dc_motor_solar Simulation Percent Difference.% 5.3% -4.6% 3.4% dc_motor Simulation Percent Difference.% -.1% -1.% -.1% Motor Rating Simulation Percent Difference.4%.%.% 3.1% Data Table : Comparison of simulated and actual data Ultra-Capacitor In an attempt to extend the life of the battery the idea came about to use an ultra-capacitor for energy storage for short term high energy demands, like the in-rush current associated with starting the DC motor. Since the internal resistance of the battery and the battery s open circuit voltage was known, a PSpice simulation was run to determine what would happen if the uncharged ultra-capacitor was placed across the battery (Schematic 6). It turns out that a large amount of current is drawn for a significant amount of time due to the large capacitance of the ultra-capacitor (Plot 8). R_Battery V_Battery 1Vdc.19 ESR.19 Ultra_Cap 58 Schematic 6: Charging the ultra-capacitor without current limiting resistor

13 1A 5A A s 1s s 3s 4s 5s 6s I(R_Battery) Time Plot 8: High ultra-capacitor charging current due to lack of current limiting resistor To limit this charging current, a current limiting resistor needs to be added to the circuit. The parameters that were used to determine the appropriate resistor value were physical resistor size, power dissipation, and charging time. The larger the resistance, the smaller the resistors became because they had to dissipate less power, but this also increased the charging time. Likewise, the smaller the resistance, the larger the resistors become to dissipate a larger amount of power. To narrow down the options a total charging time of 15 minutes was determined to be an acceptable charging time, which equals five time constants. The required resistance value to yield this charging time was calculated as follows: sec ( 15min) 6 = = = min 5τ 5RC 15min R = 3. 1Ω 5 58F ()( ) Now that knowing a resistance of around 3Ω was needed to produce a charging time of 15 minutes, the power rating of the resistor could be calculated by using the nominal 1 volts of the battery. ( 1V ) V P = = = 48W R 3Ω Using the calculated resistance and power rating, an Ohmite 7 series 3Ω 5W resistor was determined to be a good choice. Ideally the PV array should charge the ultra-capacitor instead of the battery. The problem with this is that the output of the DC-DC converter is usually between 13V and 14V. So the resistor needs to be able to handle the higher power dissipation due to the higher output voltage of the converter. The resistor s datasheet states the resistor can take an overload of 1 times rated power for 5 seconds without damaging the resistor. A simulation was conducted using a 14V source simulating the DC-DC convert (Schematic 7), plotting the charging current and resistor power dissipation as a function of time (Plot 9). From the simulation one can conclude that the resistor can handle the increased power dissipation, since

14 the maximum power is only 1.3 times the rated value and decays to the rated value in about seconds. R_Charging V_Conv erter 14Vdc 3 ESR.19 Ultra_Cap 58 Schematic 7: Charging the ultra-capacitor with PV array using current limiting resistor s 5s 1s 15s s 5s 3s 35s 4s 45s 5s W(R_Charging) I(R_Charging) Time Plot 9: Charging current and power dissipated by the 3Ω current limiting resistor Operating Mode PCB Once the ultra-capacitor is charged to the same voltage as the battery, there is no need for the current limiting resistor. So a circuit needed to be developed that could switch a current limiting resistor in and out of the system. Since we are still in the prototype phase of the project we might have to remove the ultra-capacitor at some point, so there should be a provision to safely discharge the capacitor. So the circuit will have three different modes of operation called normal, charging, and discharging, and will be known as the operating mode PCB (Schematic 8). In normal mode power will come from the battery and pass through the board to the charged capacitor and the load bus (Schematic 9). During the charging mode a 3Ω resistor will be placed in series with the battery and capacitor to limit the initial charging current of the uncharged ultracapacitor (Schematic 1). When in the discharge mode the ultra-capacitor will be isolated from the battery and connect to ground through a 3Ω resistor (Schematic 11). Power MOSFETs will be used to act as the switches on the operating mode PCB. The switching of the circuit will be controlled by the computer, so the board must be able to interface with the NiDAQ s.

15 S S3 S1 Charging Resistor To Load Bus Battery DC to DC Converter S Ultra Capacitor Discharging Resistor Schematic 8: Simplified version of the operating mode PCB S S3 S1 Charging Resistor To Load Bus Battery DC to DC Converter S Ultra Capacitor Discharging Resistor Schematic 9: Operating mode PCB in normal mode

16 S S3 S1 Charging Resistor To Load Bus Battery DC to DC Converter S Ultra Capacitor Discharging Resistor Schematic 1: Operating mode PCB in charging mode S S3 S1 Charging Resistor To Load Bus Battery DC to DC Converter S Ultra Capacitor Discharging Resistor Schematic 11: Operating mode PCB in discharge mode The actual circuit is obviously more complicated than the simplified versions above, and was constructed on a six by eight inch board. Schematics 1 and 13 show the component connections on the PCB, while the rest of this section explains how components were selected.

17 BATTERY C8.1u U5 LM937ET-8. 1 IN GND OUT 3 LM937ET-5. U6 1 IN OUT GND 3 GND C1 1u C11 1u C9 1u BATTERY C15 1u U7 8 C1+ C1- C+ C- Vcc GND 4 Vout MAX18 5 C1 1u R4 51k C13.1u C14 1u U8 Output Output Output Output Output Output 14 Vcc GND 7 SN746N Inveter Input Input Input Input Input Input S S1 S LOAD VOLTAGE GND Switch S3 IRF84 R7 1k Header f rom NiDAQ MAIN LINE Schematic 1: First half of the operating mode PCB U1 LM937ET-8. MAIN LINE GND C5 1u C6 1u C 1u C17 1u MAIN LINE U3 C1+ C+ C1- C- 8 Vcc GND 4 Vout MAX6 C1.1u 5 1 IN C7 1u C16 1u GND OUT R1 51k 3 R 51k R3 51k LM937ET-3.3 U 1 IN OUT C3.1u C18 1u GND C4 1u U4 Output Output Output Output Output Output 14 Vcc GND MM74C9X Buffer Input Input Input Input Input Output LOAD VOLTAGE S S1 S U OS - LM741 7 V+ V- 4 OUT OS Switch S IRF84 R9 1k Switch S1 IRF54 R8 1k Switch S IRF54 R1 1k 7 R6 R5 Charging 3 Discharge 3 51k 51k Schematic 13: Second half of the operating mode PCB ULTRA-CAPACITOR AND LOAD BUS

18 MOSFET Selection An IRF84S power MOSFET was selected for switches S and S3, which are connected to the high current traces of the operating mode PCB. These MOSFET need to be rated for at least 3A continuous, with low on resistance to make the voltage drop across the MOSFETs as small as possible. The MOSFETs have a continuous drain current rating of 75A, and an on resistance of.5mω, so the voltage drop across each MOSFET will be 7mV at 3A. A D pak package was used in order to increase the surface area that will carry the high current. The drain terminal on this package has a large flat surface that gets soldered directly to the board, which should also help to dissipate heat. The selection of switches S an S1 was not as critical as switches S and S3, since the will not have high current flowing through them. They also do not need a low on resistance, since they are only being used to charge and discharge the ultra-capacitor. An IRF54PBF power MOSFET rated for 8A and an on resistance of 77mΩ was selected. Since only a small amount of current will flow through these MOSFETs, a TO- was used to save board space. Gate Driver Selection Since the source terminal of the MOSFETs used for switches S1, S, and S3 will be around 1 V when the switches are on, the gate voltage must be higher than 1V to turn the MOSFETs on. A Maxim MAX6 high-side power supply was selected to generate a gate voltage above 1V. The output voltage of the MAX6 is 11V higher than MAX6 supply voltage. Voltage Regulators The maximum gate to source voltage of the MOSFETs is V. If the MAX6 was supplied by the battery the output voltage would be the battery voltage plus 11V, which could be as high as 5V if the battery is being charged and the DC-DC converter is outputting 14V. This would cause the gate to source junction to breakdown if the source of the MOSFETs were ever grounded during a fault, or in the case of switch S connected to ground through the discharging resistor to discharge the ultra-capacitor. So an 8V regulator was selected for the MAX6 s Vcc to limit the voltage output to 19V. It turns out that even though the NiDAQ s are supposed to output 5V for a high signal, they realistically can output as low as V according to Eran Tal s thesis. So a 3.3V regulator was used for the buffer s Vcc, to work with the NiDAQ s low V OH. However the inverter has a 5V regulator for Vcc, which has a V IH minimum of V, so it is compatible with the NiDAQ s. Buffer/Inverter Selection The control signals will comes out of the NiDAQs and to the inputs of either a buffer or inverter. A MM74C96 open drain buffer was used, so that when the input is high the output is floating.

19 And a SN746 open collector inverter was used, so that when the input is low the output is floating. The outputs are connect to the MAX6 s output by a 51kΩ resistor. When the inverter or buffer s output is low the MOSFETs are turned off, and when the outputs are floating the MOSFET s gate voltage will be 19V turning them on. In an effort to make the PCB more reliable it needed to be determined if there are any conditions that could cause the NiDAQ s to function strangely, and turn on a switch that should be off. It turns out there are two conditions. When the computer is initially turned on the NiDAQ s output a high signal, which remains high until the program controlling the circuit switching is executed. If all the gates are driven by buffers connected to the NiDAQ, then all the MOSFETS turn on. Which means the battery will be connected to ground through a 3Ω resistor. So the idea of using inverters instead of a buffer to control the switching came up, but this yield a new problem. If the NiDAQs loose power their output is low, which will cause the inverters (powered by the battery) to output high turning all the switches on. So an extra switch (S3) was added to the board to eliminate the problem of turning on switches when they should be off. The board is set up so that the gate on switch S3 is connected to the NiDAQs through an inverter, and the control circuitry is powered directly by the battery. Whereas the gate on switch S, S1, and S is connected to the NiDAQs through a buffer and the control circuitry is powered up only when switch S3 is on. This way when the NiDAQs are initially turned on and all outputs are high switch S3 is turned off, which de-energizes the control circuitry of switch S, S1, and S turning them off. If the NiDAQs loose power and all outputs go low switch S, S1, and S turn off, while switch S3 turns on. The best solution for this problem would be to purchase new NiDAQs that output low when initially energized, which means the board can function properly by only using buffers to interface with the NiDAQs. This way the cost and size of the board can be reduced by eliminating a number of components that will no longer be needed, such as switch S3 and all of its control circuitry. Operating Mode PCB Testing Once the operating mode PCB was constructed it needed to be tested before being installed on the SuPER cart. Since there are no power supplies that can supply 3A, the DC source from the AC machines lab was used. Data Table 3 shows voltage drop across switches S and S3 and the calculated MOSFET on resistance at different current values. I (A) S (mv) S3 (mv) R ds on S3 (mω) R ds on S (mω)

20 Data Table 3: MOSFET on resistance of switch S and S3 Plot 1 shows the voltage drop across each as a function of current. The slope of the trend line represents the average on resistance, and this value could be used to describe the MOSFETs resistance for simulation purposes. Voltage Drop Across MOSFETS 8 7 S3 S y =.4199x Voltage Drop (mv) y =.1147x Current (A) Plot 1: Voltage drop across switch S and S3 DC Motor Model with Ultra-Capacitor Simulation Although there is no data to prove how well the simulation compares to actual results, the circuit (Schematic 14) was simulated to get an idea of how the circuit might behave when the DC motor is started with the ultra-capacitor connected. The in-rush DC motor current peaks at about 6A, with the battery suppling about 8A and the ultra-capacitor supplying about 54A. By looking at Plot 13 the DC motor s torque reaches steady state in about.5 seconds. However, according to Plot 15 the speed doesn t reach steady state until 35 seconds after start up which seems rather long. If the circuit does behave like the simulation, then the battery is definitely not suppling a large amount of current during motor start up. The bulk of the current is coming from the ultracapacitor.

21 R_Battery.19 1 L_Motor.7m V_Battery ESR.19 Ultra-Cap 58 R_Motor.16 Back_EMF Km= Torque Kt= Coulomb_Drag Inertia 1. Viscous_Drag.9458 Schematic 14: DC motor simulation with ultra-capacitor s 5s 1s 15s s 5s 3s 35s 4s 45s 5s 55s 6s I(R_Battery) I(ESR) I(L_Motor) V(Ultra-Cap:+) Time Plot 11: Ultra-capacitor voltage and battery, ultra-capacitor, and DC motor current at steady state

22 8A 6A 4A A A s.1s.s.3s.4s.5s.6s.7s.8s.9s 1.s I(R_Battery) I(ESR) I(L_Motor) Time Plot 1: Battery, ultra-capacitor, and DC motor current during in-rush 3V V 1V V s.1s.s.3s.4s.5s.6s.7s.8s.9s 1.s V(Torque:3) Time Plot 13: Modeled DC motor s torque in lb-in with ultra-capacitor

23 1.5A 1.A.5A A s.1s.s.3s.4s.5s.6s.7s.8s.9s 1.s I(Coulomb_Drag) Time Plot 14: Modeled DC motor s peak speed in krpm with ultra-capacitor 1.5A 1.A.5A A s 1s s 3s 4s 5s 6s I(Coulomb_Drag) Time Plot 15: Modeled DC motor s steady state speed in krpm with ultra-capacitor

24 Parts List Description Part # Newark Part # Price R1 51kΩ MCRC1/4G513JT-RH 73K R 51kΩ MCRC1/4G513JT-RH 73K R3 51kΩ MCRC1/4G513JT-RH 73K R4 51kΩ MCRC1/4G513JT-RH 73K R5 51kΩ MCRC1/4G513JT-RH 73K R6 51kΩ MCRC1/4G513JT-RH 73K R7 1kΩ MCRC1/4G1JT-RH 7K R8 1kΩ MCRC1/4G1JT-RH 7K R9 1kΩ MCRC1/4G1JT-RH 7K R1 1kΩ MCRC1/4G1JT-RH 7K Total 1.8 Description Part # Newark Part # Price C1.1μF KME5VBR1M5X11LL 91F C 1 μf 16CKH1M 69K C3.1 μf KME5VBR1M5X11LL 91F C4 1 μf 16CKH1M 69K C5 1 μf 15CKH5M 69K C6 1 μf 15CKH5M 69K C7 1 μf 15CKH5M 69K C8.1 μf KME5VBR1M5X11LL 91F C9 1 μf 16CKH1M 69K C1 1 μf 15CKH5M 69K C11 1 μf 15CKH5M 69K C1 1 μf 15CKH5M 69K C13.1 μf KME5VBR1M5X11LL 91F C14 1 μf 16CKH1M 69K C15 1 μf 15CKH5M 69K C16 1 μf 15CKH5M 69K C17 1 μf 15CKH5M 69K C18 1 μf 15CKH5M 69K Total 1.38 Description Part # Mouser Part # Price X1 15 amp terminal X 15 amp terminal X3 15 amp terminal X4 15 amp terminal X5 3 amp terminal X6 3 amp terminal X7 3 amp terminal Total 5.56

25 Description Part # Newark Part # Price U1 8V Regulator LM937ET-8. 7B U 3.3V Regulator LM937ET K U3 High-Side Power Supply MAX6 U4 Buffer MM74C96N 58K U5 8V Regulator LM937ET-8. 7B U6 5V Regulator LM937ET-5. 41K U7 High-Side Power Supply MAX18 U8 Inverter SN746N 8F U9 MOSFET IRF54PBF 63J73 1. U1 MOSFET IRF54PBF 63J73 1. U15 MOSFET IRF84SPBF 73K U16 MOSFET IRF84SPBF 73K U17 Op Amp LM741 78K61.96 Total 3.38 Description Part # Newark Part # Mouser Part # Quantity Price Total 3 ohm 5W L5J3RE 64K Crimp Connector K terminal housing terminal header Total How to Operate the SuPER Cart SuPER Prototype Operation Modified 6/11/7 J. Witts 1) Ensure that all breakers are open. ) Insert the hub cables into the laptop USB ports, followed by the NI DAQ device cables. Then insert the PIC cable into the open laptop port. The mouse cable should be inserted into the hub. 3) Power on the laptop (at this point running on its internal battery) and at the GRUB window choose the latest version of Red Hat. 4) Login using root:super1. 5) Open a shell and change directories (cd) to /home/super1/pvpro/src to control the PV and main switch board. 6) Close PV, converter and battery circuits by flipping the breakers marked PV, BATT and BUS. The PV array will start charging the battery even though no programs are running, because the NiDAQ s default output is high (turning MOSFET switches on). 7) Execute the software with the command./contacquirenchan. 8) Open a new shell and change directories (cd) to /home/super1/cap/src to control the ultra-capacitor board. 9) Execute the software with the command./cap.

26 1) If the ultra-capacitor is not needed leave the breaker labeled CAP open, enter n to operate the capacitor board in normal operation, and skip to step 14. If the capacitor is needed proceed to step ) Check the capacitor voltage with a voltmeter. If the capacitor voltage is within V of the battery terminal voltage, run the capacitor board in normal mode. If the capacitor voltage is not, run the capacitor board in charging mode. Once the capacitor voltage is within V of the battery terminal voltage, change the operating mode from charging to normal. Follow prompt and enter correct mode of operation. c to charge the capacitor (used if capacitor is not at battery voltage) n for normal operation (used to operate the cart without any resistors) 1) Once the capacitor board is operating in the correct mode determined from step 11, close the breaker labeled CAP. Once the capacitor is at the same voltage as the battery node and the operating mode is set to normal, the SuPER cart is ready to operate 13) Close the breakers as desired to power indicated loads. 14) To turn the system off, open all circuit breakers connected to the load bus. 15) While in the shell for the ultra-capacitor board type o to turn all switches off (used to turn all capacitor board switches off) then q to quit (used to exit program) 16) Now go to the shell running the PV software and use q to quit. 17) Shut everything down by opening all circuits at the breakers. Note: If the ultra-capacitor has to be physically taken off the cart it must be discharged first. Follow the instructions below to safely disconnect the ultra-capacitor. 1) Follow steps 1 through 4 listed above. ) Close the breaker labeled BATT. 3) Follow steps 8 through 9 to run the ultra-capacitor board software. Set the board to run in discharge mode by entering d. 4) Close the breaker labeled CAP. 5) When capacitor is fully discharged (use voltmeter to ensure V) turn off the system following step 15 listed above. The capacitor can now be safely removed. Circuit Breaker Rearrangement In order to connect the capacitor to the SuPER cart, some of the circuit breakers needed to be moved. The amp circuit breaker labeled BUS, that powers the sensors and control elements, had to be removed from the load bus. When the ultra-capacitor is charging it pulls the bus voltage down to zero volts, then slowly rises to the battery s voltage. When the voltage is pulled down to zero, none of the control circuitry can be used. This means the PV array cannot be used to charge the ultra-capacitor, only the battery will be able to charge the ultra-capacitor. So by moving the BUS circuit breaker off the load bus and powering it off the battery, the PV array can now be used to charge the ultra-capacitor.

27 A 6 amp circuit breaker was selected to protect the capacitor. The breaker size was selected based on looking at the simulated capacitor current during start up (plot 1), and compared to the circuit breaker curve of plot 16. Since the circuit breaker curve is based on constant current during a fault, the breaker should not operate for the decaying transient of the DC motor s inrush current. The ultra-capacitors circuit breaker could not be directly connected to the load bus, since the circuit breakers can only interrupt faults in one direction. The construction of the circuit breaker only allows mounting in one direction, so it had to be installed adjacent to the load bus. See Schematic 15 for actual breaker locations. The circuit breaker was connected this way to interrupt fault current supplied by the ultra-capacitor if the load bus, or any point connected to the load bus, was faulted to ground. Plot 16: CBI circuit breaker curve

28 Schematic 15: Gavin Baskin s SuPER schematic