This is from Toshiba, Application Guideline #4 indicated common causes of motor failures, and it was determined that temperature kills motors. Ideally, a motor should have a relatively high insulation temperature rating, and a relatively low operating temperature for both the insulation system and bearing system. This provides for thermal margin in the event of motor overload, severe starting duty, safety margin for adjustable speed drive applications and for many other reasons indicated in ‘Application Guideline #4’. (A well-accepted rule of thumb is that for every 10°C, that the motor temperature exceeds its rated insulation temperature, the insulation life is reduced by half, likewise for every 10°C cooler, the insulation life is doubled.)
The information you seek may be here: http://priuschat.com/forums/gen-iii...ion/75554-observed-temperatures-x-gauges.html
From the 2010 Repair Manual: Measurement Item/Display Range (Not operating range) : MG1 temperature / Min.: -40°F (-40°C), Max.: 419°F (215°C) While driving at an ambient temperature of 77°F (25°C): 77°F (25°C) to 212°F (100°C) So the 204F is within normal range. I have seen about 195F on mine with similar driving. MG1 runs about 20F hotter than MG2 in most instances that I have observed.
It is not an operating temperature range, but it is a display range of 8 bit value. An 8 bit value can display between 0 to 255, and the temperature value has -40C offset, so it can display between -40C and 215C. On the JP service manual, the warning threshold is clearly stated as 162C (324F). Ken@Japan
Just to clarify, the 2010 Repair Manual also show 334.4°F (168°C) and 323.6°F (162°C) for MG1 and MG2 respectively. It is the same Class H motor winding as Gen 2. Vincent
Ken, Thanks for pointing that out. I should have labeled it as a display range, as it is in the Repair Manual, so it would not be mistaken for an operating range. The second line was the more appropriate information which listed the normal orperating range at 77F. Dwight
On the same manual, the engine coolant temperature (THW) is also shown as Min.: -40°F (-40°C), Max.: 419°F (215°C). I don't think 215°C coolant temperature is acceptable. Ken@Japan