What IS the maximum acceptable inverter temp??

From the "operation history data" part of the repair manual, which
details various recorded out-of-bounds measurements [for '04] ...
.
_ MG2 (NO 1) TEMP HI -- motor temp above 174C (345F)
_ MG2 (NO 2) TEMP HI -- trans. fluid temp above 162C (324F)
_ MG2 INV TEMP HI -- motor inverter rose above 111C (232F)
_ MG1 INV TEMP HI -- generator inverter rose above 111C (232F)
_ CONVERTER HEAT -- boost converter temp rose above 111C (232F)
_ COOLANT HEAT -- inverter coolant forecast temp above 65C (149F)
.
I have no idea what "forecast temperature" is, but it looks like
the inverter's coolant loop is expected to stay on the cool side.
.
This is supposedly data that the ECU would store long-term so a tech
could hook up a scantool and make judgements about your driving
style. Some of the items are a bit big-brotherish or just don't
make any sense, such as if you pressed the accelerator while in
Neutral [bfd] or my favorite,
_ PREVENT STAYING -- engine speed stays in resonance frequency band
which I've *never* gotten an answer on what the F it means.
.
anyways, hope this helps. It's all in the TIS stuff.
.
_H*

 

On the electricals side, I stongly suggest 'the lower the better'. In nhw11 Prius I don't think I ever saw inverter temperatures above low-90s oC. Note that this is not a pressurized coolant system and it you ever got above 105 oC, you would be pressure-testing it. Probably a bad hobby.

All that is separate from what the inverter semiconductors can tolerate safely, and uninformative on when the computers might act to put you into some sort of limp home mode.

Max noted for MG1 (which ran hotter in mine) was 105 oC or so, and rare. An MG2 failure recently reported here was concurrent with 160 oC recorded. So don't do that!

 

<div class='quotetop'>QUOTE(tochatihu @ Sep 16 2007, 08:20 PM) [snapback]513502[/snapback]</div>

I was worried last summer when driving at freeway speeds (70-75 mph) in external temperatures arround 100F for an extended period of time the higher of the 2 (I don't remember whether it was MG1 or MG2) reached 184F. This was between Winnemucca and Reno. I don't know whether the altitude was relevant or not. That's the only times I've seen either inverter temperature above 160F. Usually, it's much lower than that.

This was according to CAN-View, and I never noticed a problem with performance or any lights on the dash indicating a problem.
Is the fluid in the motor generators and the transaxle the same? I'm approaching 60k miles, and thinking about replacing the tranaxle fluid.

Dave M.

 

thanks for the info!!i needed it for a while

 

Is there a way to check the mig I & II temperatures through any of the MFD screens.

If not where can I get the CAn-View tool?
I have found the Scan-Gauge II, but cannot tell if the ScanGauge tells me Mig temps.

 

I'm going to get a little technical here, and I won't be giving you a set point to avoid, because I haven't done the detailed calculations as I don't have the technical design documents the Toyota engineers used. But for purposes of better understanding and perhaps to scare us all....

There will be other limits, but the one that concerns me is the maximum junction temp. of the power semiconductors in the inverter. Being silicon, they will be rated at about 200 deg. C max, but you have to "derate" their power handling capacity when you get the junction temp. above 25C. The graph almost always looks the same - on a graph with power in the vertical axis and junction temp. on the horizontal, draw a horizontal line at the max. power handling point to 25C, then diagonally down to 0 W at the 200C point on the horizontal axis. Be aware there is some thermal resistance between the junction and the case, and more between the case and the heatsink (the inverter coolant in the case of the Prius). If you are unfamiliar with the term, you multiply the added together thermal resistances from junction to heatsink by the power being handled to get the temp. rise across that "gap". This often results in a 200W semiconductor being only able to handle 100W or less at operating temps.

I'm sure the engineers left plenty of room for the temp to wander up, as that is what they do. But something to consider when wondering "how hot can it get before it goes poof". Also stated "don't let the smoke out!"

 

I suppose only as a rule of thump you schould not move much above 100C, thats the temp most CPUs and GPUs can handle...

I know it can not compared directly, but not forget all the condensators on the inverter board... I suppose they do not like an ambient temp much above 80C, if only one condensator spills his electrolyte out of his vent the inverter is screwed....

Andreas

 

Usually the gain of semiconductors drops with elevated temps. This is one of the parameters the engineers must take into account when designing the circuit. So that's one.

Then there is the problem that most of the "conductors" laid down on the die of the semiconductor are aluminum (copper is used sometimes, but precautions have to be taken, as copper is "toxic" to silicon semiconductors). Aluminum will flow in a DC current, and does so faster at elevated temps. This thins out the conductors, and eventually they go into thermal "runaway" (as they get thinner they run hotter, making them get thinner faster, making them get hotter faster.....and they burn out - open circuit, meaning the semiconductor fails). This is one of the main failure modes of micro-processors, but not of power semiconductors, mainly because there is usually room and incentive to make the conductors much larger than they need to be. So you end up with a "life limiting" problem, the hotter you operate the device, the shorter its' life. That's two.

Then there is the most important design parameter for the power semiconductor, the "safe operating area (SOA)". Again, it's plotted as a graph, which looks much like the max. power handling graph, and you absolutely positively MUST stay under the graph line! Failure to do so results in catastrophic sudden failure, literally with smoke and flames (and case destruction)! The SOA is also reduced with temperature. The design engineers tread very carefully here, I know I did whenever I designed a power circuit. I was known to parallel three or more devices (with "ballasting" resistors to ensure the power was shared properly) to ensure I had a 3 to 1 safe margin! The devices were cheap, failure was usually very expensive! I'm betting the Toyota engineers were also very conservative, based on lack of failures in places like Texas and Arizona. So that's three!

There are others, less important perhaps, but it appears the inverter is very well designed, so I think if you stay below the temps already mentioned above in this thread you should be fine.

I haven't programmed my Scangauge to watch inverter temps, perhaps because I don't want to be scared by what I would see. "Head in the sand" syndrome.

I install grill blocking in September, once ambient temps stay below about 15C. I have driven with the grill blocks in, both city and highway, in 20C temps, with engine coolant staying below 105C. The system won't boil until it gets above about 120C (from calculation, not experience!).

 

I just want to clarify that the high 90s C temperature that I saw as a max (2001 Prius) was from MG1. MG2 max observed was perhaps low 90s C, and the inverter coolant (in inverters 1 and 2) was not seen above the 80s C.

For getting coolants to boil (an undesirable condition!) That would happen at lower temperature in the electrical loop because it is not designed for overpressure. The value may be about 120 C as David suggests, just based on the coolant chemistry. The engine coolant loop will hold pressure to about 14 psi above air pressure (and then the radiator cap valve opens). This should translate into a higher acceptable operating temperature on the engine loop, but I assume that nobody really wants to pressure test their hoses and connections in this way.

One has to work a Prius quite hard to get into the temperature regimes worth discussing. Many drivers never will. However, I would certainly welcome a more informative display, so that under severve operations, we could know better when we are approaching such conditions.

 

I just wanted to bump Hobbits post http://priuschat.com/forums/gen-ii-...imum-acceptable-inverter-temp.html#post491484 because I see a lot of people asking similar questions about temps.

From what I've read the ICE tries to stay below 80C and the MG2 and MG1 should be under 60C with highest reported normal readings under worst case as 100C.

I found the same thing in the Repair Manual. These are the limits where the HV ECU increments a counter for each of these events. The dealer can read the count with their Intelligent Tester II -> Powertrain/Hybrid Control/Data List

MG2 temp above 174C
Transaxle fluid temp above 162C
MG2 Inverter temp above 111C
MG1 temp above 111C
MG1 Inverter above 111C
Boost Converter temp climbed above 111C
Inverter Coolant temp climbed above 65C
Limit Resistor temp above 120C
Aux battery below 9.5V
Main battery SoC dropped below 30%
Instantaneous open detected at IGSW on HV ECU
Shift lever moved while READY blinking
N position control affected by frequency shifting
Accelerator depressed while in N
Shifted to P while driving
Shifted to R while moving forwards
Engine speed stays in resonance frequency band