SYSTEM COMPONENTS
Wampfler® IPT Equipment
The following describes the components of the Wampfler® IPT system and how they relate to the testing UTC will be conducting. Detailed installation instructions can be found in the Wampfler® documentation, but this gives an over view of how the parts relate.
A three-phase isolation transformer is placed between the input from the power pole and the track supply to prevent electrical noise and isolate the system electrically. An isolation transformer has a 1:1 turn ratio, and thus no different between the input and output voltages.
Figure 1: Track Supply
The track supply takes the 400v 60hz 3-phase power input and converts it to a 20khz 0 to 600v output going to the primary coil providing power to the bus. The tack supply can support one or two primary coils and 30kw or 60kw of power transfer respectively. The unit is self cooled using and output power via two litz cables. In the case of UTC, only one primary coil will be sued for testing purposes.
The track supply can be started and controlled there manually from the LCD and external controller to provide or remotely from the bus via the RBCI. To communicate to the RBCI, the track supply is attached to a 2.4ghz radio modem via the RS-232 port on the top. This modem is described below. Control inputs for the manual start and indicators are provided on a 10-pin HAN connector.
Before the track supply can be used, Wampfler personnel must commission the supply and input a PIN number to activate the unit via the front LCD screen. After this is done further configuration of the track supply, including settings for manual operation, and be done via this LCD.
A capacitor box is places in parallel across the output from the track supply. The capacitor is there to tune the system to approximately 70khz in order to get the most efficacy from the system. This forms a RLC circuit with the primary coil and track supply thevenin inductance being the inductor (L), the cables and track supply thevenin resistor being the resistor (R) and the capacitor box (C). The equation for the resonance frequency can be seen below.
RLC Circuit Resonance Frequency
Through the values of L and C are not given, they can be checked using a proper meter. The product of L and C should be close to
to tune the system to 70kHz. If one capacitor is not enough to do this, an additional one can be put in parallel.
This capacitor is air cooled using it’s own internal rectifier and needs no hookups except the Litz cables going to the primary coil.
Figure 2: Primary Coil
The primary coil is encased in a 1600lb concrete block placed in the ground under were the bus will charge. This coil
takes the input power from the track supply and converts it to a magnetic field used to transmit power to the secondary over set air gap. Power enters the coil through a set of litz cables that are spliced into the single cable going to the track supply. The primary coil is water-cooled requiring a 0.3 gpm flow rate using the system described below.
The concrete the coil is incased in is capable of withstanding normal road traffic with vehicles up to a 22000lb wheel loading. This needs to be placed a in the ground even with the road and in such a way the bus can repeatably position the secondary coil relative to it within limits.
A 120Vac powered liquid cooling system is provided with the equipment to cool the primary coil. It outputs coolant via two 35mm tubes at .3gpm and can handle the 500w of heat that needs to be dissipated from the primary coil.
Figure 3: Secondary Coil
The secondary coil is attached to the bottom of the bus to convert the magnetic field produced by the primary into current for the charging system. The secondary coil is rated at 100A at 300Vac and 30kW of output power. The output of the coil is in the forum of two pairs of 35mm litz cables within flexible conduit. These are wired into the input of the rectifier.
The stated tolerances of the alignment of the center of the secondary coil to that or the primary are as follows: Horizontal +/- 50mm, Vertical +/- 10mm, Longitudinally +/- 50mm. The coil has a nominal distance from the secondary of 40mm.
Figure 4: Rectifier
The rectifier takes the 20khz AC signal from the secondary coil and converts it to DC to charge the batteries. The particular rectifiers that UTC has are rated at outputting 100Adc at 300V giving a 30kW to the batteries. This output voltage is adjustable on the track supply with this rectifier capable of 0 to 450V dc output. If the voltage exceeds 450V the over voltage relay will activate.
Cooling is provided to the rectifier via 10mm liquid cooling inlet and outlet. Water at 8 l/min is pumped through the rectifier and into a radiator system capable of expelling 400W or more. If the coolant liquid exceeds 50C it will trip the over temperature relay will activate.
The error relays connections and rectifier output are located in a single 13 pin HAN connector that connects to energy storage and management systems. This connector also contains the hookups to the battery
Figure 5: Remote Battery Charger Interface
The Remote Battery Charger Interface (RBCI) provides control and feedback on the charging process from the bus side of the system. It monitors voltage an current coming in from the rectifier along with communicating with other bus side systems.
The RBCI is powered by a 24v supply typically provided by the bus. In the case of this testing, this power will need to be supplied by an independent 120vac input 2A 24V power supply. This was not included with the Wampfler equipment and will need to be purchased if testing with the RBCI.
Communicating between bus systems and the RBCI is handled over a SAE J1850 bus on the HAN 42DD connector. This bus is used to enquire from the bus if it is in a state ready to charge and how much energy the bus needs. The ENOVA BCU will be used. Communications between the RBCI and the track supply is handled over a radio modem attached to the serial connector. This communications tells the track supply
To measure the charging parameters, the RBCI has an inductive current pickup that is put over one cable on the output of the rectifier. It is also takes the battery voltage in through two current limiting resistors. Other connections into the RBCI include the “start” button that initiates communication and power request, error inputs from the rectifier, inputs from the BCU, and outputs for error indicators for the operator.
The XStream RF modem provides an RS-232 serial interface between the RBCI and the track supply. This is used to request the amount of power the bus wants, provide feedback about the output of the secondary, and start or stop charging. The particular modems used operate at 2.4ghz and have a range of up to 3 miles line of sight or 600ft in an urban setting, more then adequate for this application.
The 12V+ or the RBCI or other available 12V power bus will provide power on the bus side. On the track supply, a standard “wall wart” power supply will be used. The radio modem connects to the RBCI via the special rs232 cable adapter provided by Wampfler®. On the track supply, it’s connected with a standard rs-233 cable.
The battery care unit manages the battery bank and provides an interface between the IPT system and the rest of the controls on the bus. This unit is connected to the RBCI through the SAE J1850 bus. It’s capable of monitoring individual battery bank voltages, temperatures, and stats of charge to communicate with a SAE J1773 compatible Inductive Coupled Charging system.
For additional communication and control, the BCU will be hooked to an IR rs-232 transceiver to allow remote management. In the SAE J1773 standard this IR interface is typically used to indicate the state of charge to the charging system. With the Wampfler® equipment, this is handled over the SAE J1850 bus and the RF modem.
At this time UTC does not have a BCU. One will need to be purchased for the system to operate with feedback from the RBCI. The typical BCU that Wampfler® uses in these applications is the ENOVA energy management system.
CARTA® is providing UTC with a spare set of batteries to charge for testing. The batteries that CARTA® uses are Deka® 81-P71-7 213ah and Hawker® 162P0195 195ah batteries. With the 100A output, this will be charging the batteries at twice the C/4 rate commonly stated to be the max for flooded lead acid batteries, but should acceptable for short periods of time according to the staff at CARTA®.
Figure 6: ABC -150
The ABC-150 is a bi-direction power processing system designed to test drive train components of electric vehicles. It was originally designed to support the GM Impact (predecessor to the EV-1), and is commonly used for testing electric vehicle batteries. It’s capable of sourcing or syncing up to 150kw of power in these tests. This power is ether sourced from the electric grid or put back based on the direction of power flow. Like the track supply, the ABC-150 is connected to the electric grid through a three-phase isolation transformer but at 240V.
For the Wampfler® IPT® testing, the ABC-150 will be used to set the starting state of charge for the CARTA® batteries. After a charging cycle is completed, the ABC-150 will simulate the load the bus presents to the batteries and discharge them to the state they would have when the bus returned to the station. The ABC-150 can be configured for thus using the front panel to discharge at a particular rate, or it can be programmed via a RS-252 port behind the back rear cover.
