Toyota Prius (2nd Gen) High Voltage System Operation

Toyota Prius (2nd Gen) High Voltage System Operation


this is a demonstration of the second generation Toyota Prius hybrid system operation as far as the electrical high voltage components in that system we have here at Weber State University a partnership with Toyota for our associate degree Toyota t-ten program and also for bachelor’s degrees in filled service operations and advanced vehicle systems and so we teach a hybrid system operation and hybrid safety to our students we’ll start with the high voltage battery that is in the back of the Prius this is a 200 1.6 volt DC nickel metal hydride battery this is an alkaline based battery the battery itself is fairly heavy and it’s located behind the backseat in between the wheel wells this battery has the computer that controls it and and of course DC cabling that leaves the battery but while we’re here on the high voltage battery notice also that we have an auxilary battery the 12-volt batteries so on all hybrid vehicles that I’m aware of we still have a 12-volt battery that needs to be charged and and runs the rest of the vehicle but the high voltage battery is is different and only is for the high voltage electric motors in the transaxle but if we look closely down inside the battery here we have positive contactors negative contactors and a pre charge a contactor think of these contactors as high voltage relays and so the orange cables coming in on the left here are from the DC high-voltage battery itself and then once the relay contacts close we connect the two terminals together with relay contacts and then apply the DC voltage to these orange cables that goes up to the front of the car to the inverter converter assembly under the hood the pre-charge capacitor is there across the negative contactor where when we close the negative contactor right before we close it we turn on this pre charged contactor which as you can see has a high wattage resistor there’s a capacitor involved where it equalizes the voltage through a capacitor across the contactors and then closes the contactors themselves to minimize arcing and prolong the life of the contactors and all hybrid batteries that I’m aware of have at least a pre charged contactor and one either positive or negative contactor this one actually has both so what that means is that these high-voltage wires here don’t have any power to them at all if the key is off and as long as those relays are off which when the when the key doesn’t have a key would when you turn the power button off and you just you turn the power off to the vehicle or if you disconnect the 12-volt battery the 12-volt system is what controls these contactors and it will open circuit D high voltage now on the back of the the side of the battery case we are also we also have a service plug grip that has to be installed in order for the battery circuit to have continuity and so when we install this we push it in rock up on the service plug grip handle and then we push down by pushing down we’ve got a little two wires circuit there the isolation circuit that lets the computer that’s in charge of the high voltage system know that the service plug is installed when we disconnect this plug we’re just going to lift up on the plug rock it out and pull it straight out and inside of this plug is a 125 amp fuse that’s actually built into the plug itself you can’t buy it separately the service plug has to be purchased by itself if the fuse for some reason is blown but we have the high voltage battery with its positive and negative contactors and the positive and negative cables but this service plug grip that we just pulled out interrupts with open circuits this series set of batteries that we have underneath the case here and I’ve got a picture I printed of the inside of the battery with multiple battery cells at seven point two volts apiece all of them in line with each other but we’ve got contactors that connect or disconnect the high voltage battery and once again those are controlled by the 12-volt system so if we follow this cable right over here and this comes up through the trunk area we have a wire that is labeled from the 12-volt battery so on our 12-volt battery right here we have the negative terminal which has just a little tiny short battery negative cable that bolts to the inner fender and then we have a positive cable that comes all the way from the inverter converter assembly now there’s a big heavy white wire on the bottom of the converter inverter assembly right there that has a wire that comes all the way back to connect to the battery positive terminal of the auxilary battery and then this also connects in there and goes all the way to the front of the vehicle on this black wire so the two orange wires are a positive and negative high voltage DC that black wire comes all the way to the front of the vehicle and right on the driver’s side underneath the hood is the under hood fuse block and this is the power feed to diffuse block itself so let’s look again we’ve got the high-voltage battery we’ve got the big heavy orange cables we go underneath the car and go all the way to the front to the power inverter converter assembly that’s normally covered with this cover right here so I’m sure you guys that have been under the hoods of hood of a Prius 2nd generation Prius recognize this battery cover or the inverter converter cover not battery cover that cover covers up a bunch of electronic components that we’re going to talk about here in just a moment but while we’re here coming off the the rear the rearward most part of the inverter converter assembly under the hood we have three-phase cabling that goes out and goes to our motor generator number two stator windings there are three sets of windings there and then I have a separate video on the second generation Prius hybrid electric motor operation but this is motor generator 2 that drives the ring gear of the transaxle and so our inverter converter assembly rear connection is what supplies power to the rotor or stator assembly to drive the mg 2 this is a whi wound of stator it also receives current during deceleration for regenerative braking and then coming off the front bottom of the converter inverter assembly we have more three-phase cabling right here that goes and drives the mg1 stator assembly this is also a wireless stator in this mock-up I’ve disconnected the center connection of the why we’re on the stator and of color-coded it for demonstration purposes with my students but mg1 is this smaller electric motor here that drives the Sun gear of the transaxle assembly and then our internal combustion engine of course drives the planet carrier but the inverter can rotor assembly here on our wall is what is in control of driving both mg 1 and mg 2 and also receiving the current from them during deceleration now this thing gets really hot and so we’ve got another inverter converter assembly that’s disassembled and we’re looking at the bottom of it here you can see the cooling passages and you can see some coolant connections we have an electric water pumps a pump also in this system it’s got its own cooling system it uses the toyota long life super long life coolant same as what’s in the radiator but to separate container systems this is the fill tank the search coolant tank for the power electronics portion of the radiator now let’s get back to the converter inverter assembly the very top piece that we’re seeing here is the big pack of capacitors and if we come over here to where I’ve got it disassembled the second one disassembled we can see the capacitor module right here on the wall and it actually has the capacitor sizes although it’s upside-down listed here the capacitors involved in this circuitry you have a 1130 microfarads 282 micro farad’s and zero point 1 micro farad capacitors there that are part of the overall motor driving circuit that is involved in this second generation Prius now right here underneath the capacitor module we have what’s called the intelligent power module the IPM well the intelligent power module has isolated gate bipolar transistors six of them so these six connections here go down and underneath and there’s a huge heatsink that connects to the coolant or the aluminum where it’s liquid cool over here those transistors are what drive our three-phase cabling so the three-phase cables that connect to the inverter module that drive mg1 connect here and that’s these three connections and then our mg 2 connection comes out over here and that’s these three wires big heavy connections we’ve got some current sensors we’ve got a computer that’s in charge of the inverse inversion of DC input we’ve got our DC input coming in right here and then this is our AC output so we’re inverting DC to AC to drive the motors and then during deceleration we’ve got six gigantic diodes in here that act as a rectifier bridge so we’ve got basically two alternators or mg 1 and mg 2 motors that are used during deceleration to apply a voltage and send current back so we go from AC back to DC we convert it and then that goes back to our high voltage battery now between the inverter converter assembly this intelligent power module we also have what’s called a reactor which is just a big coil of wire it’s an inductor and then we have another IGBT module that’s called the Burt boost converter module and it’s going to step our voltage up or down DC we have our DC power coming in here it stepped up and then fed to the inverter converter assembly but there’s two transistors and two diodes in this boost converter module and we use that to fully activate the inductor by pulling it to ground on one side providing power on the other build a huge magnetic field and then when that filled collapses we route that high voltage along with the high voltage from the battery to the inverter converter assembly and we can step the voltage up now on the second generation Prius we can step it up as high as 500 volts but that stepping up is done through this reactor as Toyota calls it and our boost converter module which is made by Mitsubishi so are in our overall schematic here we’ve got our high voltage battery right here here’s that reactor core the wire and we turn on this transistor in the boost inverter power module and we get a complete loop which energizes this reactor we build this huge magnetic field we let that we turn this transistor off and then we turn this one or no we leave that one off also when the filt collapses the polarity is positive – and through that diode we can supply the inverter converter assembly for the two motors now also excuse me in the converter inverter assembly underneath it is as you can see here in this diagram a DC to DC converter and an air-conditioning system inverter and so that is this plate right here this aluminum housing with it circuits and parts inside of it in there we have these two wires right here that are 200 1.6 volt DC input those two wires actually reach clear up through a hole right here those wires will stick up and connect to these same few wires from the DC 200 1.6 volt battery so those wires connect to the high-voltage battery they will command over and up and then we have our air conditioning system inverter so this is the same type of inverter system that we use to drive mg 1 and mg 2 it’s just in a smaller form so we have our DC cables coming in we have our three-phase cabling going out and if we follow this orange wire then we come down to our electric air conditioning compressor that is you can see with the three cables here it’s also a three-phase AC electric motor and that’s a variable speed air conditioning compressor there’s no fan belt we can speed the compressor up or down depending on the refrigerant needs and cooling needs in the evaporator so that’s our air conditioning system inverter assembly and then we also to charge the 12-volt battery system the auxilary battery here which is behind the notes in the right rear of the car we have to have a DC to DC converter assembly to take our 201 volts DC in and then run it through this center tap transformer and a series of diodes another inverter or another inductor reactor and then to the 12-volt system and with the system powered up even though we say it’s 12 volt we get around 14 to 14 and a half even as low as 13 and a half if the 12 volt battery is pretty low volts for our charging system voltage constant there is no alternator on this system this DC to DC converter is what actually drives or sorry charges the auxiliary battery on the vehicle while we’re here I’ve got some personal protective equipment that I want to show you we have some high-voltage gloves these are some old expired ones so I’ve poked a hole through them but let me take those off and show you the rating and the date on those if we can zoom in here there we go you can see these are made by Salisbury they are class zero that focused focus there we go class zero gloves which is what they need to be notice these were tested September of 2007 you’re not supposed to let these go more than six months without either replacing them or having them recertified so these gloves are no good and so I’ve got them just hanging up to show a pair of gloves in my classroom but if you wear these gloves just on your hand it’s not very long at all before you get really sweaty and so they also sell at what’s called an inner glove which is basically just a gardening glove you can get like a Home Depot that inner glove will allow your hand to breathe got an airplane going overhead allow your your hand to breathe while it’s inside of the high-voltage glove and then we protect the high-voltage glove with this leather outer glove and you should put them on both hands as you’re working on these vehicles now just let’s look at an overall let’s review just one last time overall system operation and voltages we’ve got our 200 1.6 volt DC battery that when it’s the engine is on and the mg one is rotating we make we’ve measured as high as two hundred and sixty years old bolts fed back to this to charge it but those two wires the high voltage wires go underneath the car so once again if you’re lifting the car look out that you don’t put your left host points on the cabling of course it’s in a protective housing you can see there and I’ve removed some of it just to hang it on the wall but unless the system is turned on and these contactors are closed which means you have to have your foot on the brake and hit the power button at the same time and have the ready light on on the dash unless all of that happens there is no power on these cables these are DC cables that go from the back of the car all the way up underneath the hood and those two cables connect to the inverter converter assembly right here underneath the hood there’s no power on those if the if the system if the key is off but don’t make an assumption make sure that before you disconnect or take any make well before you disconnect anything or replace anything grab a multimeter or high voltage class three 1000 volt rated meter and make sure that there’s no voltage before you put a wrench on something or or touch something but you should be wearing your personal protective equipment so that’s our DC cabling that goes all the way from the battery to ooh the inverter converter assembly underneath the hood and then we have short three-phase cabling that goes from the inverter converter assembly to our motors the mg 2 and the mg 1 those won’t have any AC power on them unless the vehicle is moving which you should never tell one of these because we’ve got a spinning magnet or set of magnets inside of a coil of wire which will create through induction of power and it’s got to have somewhere to go and you can damage the inverter converter assembly because it has nowhere to go but those cables won’t have any power on it unless the vehicle is moving or if the engine is running mg one right here will be can be spinning and acting as a generator and probably will be spending if the engines running to have a AC voltage that’s converted to DC and sent back to our high voltage battery for charging and then it’s a high voltage battery through the DC to DC converter that steps it down and charges the auxilary battery the the 12-volt battery in the back of the car so on this system if you need to disable it quickly for whatever reason just disconnect the negative and a battery cable if you can get to it make sure the power is off turn the power or hit the power button to shut the system off as long as the power is off there should be no power or as long as the power button is often the ready light is off there should be no power on any of those orange cables nothing everything should have zero volts on them but if in an accident you need to disable the system since the 12-volt battery is in the trunk area that you can’t get to very easily we rely on these contactors to go open to make the system be disabled but if you can get the trunk area open you can get to the battery to disconnect it or you can get to that service plug plug grip and disconnect it as I showed you to disable the system but you don’t need to be really afraid to work on one of these don’t panic don’t think that just because you touch an orange cable that you’re going to die that’s simply not the case but don’t make assumptions that there’s no power there either although probably in most cases as I said if the ready light is off the engine is off the keys are gone and you’re not towing the vehicle there would be no power there anyway so this has been a demonstration of the hybrid system of a 2004 through 2009 Toyota Prius this is the second generation system the first generation system is very similar and the third generation system is very similar but the third generation system I’ve got some photos over here third generation system the power inverter module is a much smaller module the second generation one is on the left third generation ones on the right and then these electric motor mg 1 and mg 2 assemblies the ones on the left are the second generation Prius the ones on the right are the third generation Prius and these photographs are off of Toyotas press website that are freely distributed distributable and then also the the second generation on the left third generation on the right the in the electric motor pack assembly in the transaxle the third generation transaxle has an additional planetary gearset for reduction for the mg 2 motor which allows the motor to be smaller spin faster and have higher torque and higher output and as you can see in this picture here the second generation mg 2 is huge really wide and the third generation is much narrower we also got rid of the chain Drive in the second generation and went right to a gear drive in the third generation and this is a transaxle housing split apart where the motor assemblies of come out of so this has been a demonstration of the operation of the high-voltage hybrid systems of a Toyota Prius 2004 through 2009


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