Improvement #2: cooling the motors - Liquid


How can we improve the cooling system?

The first step is to take a close look at the liquid cooling system.
We take apart the Siemens motor and track the coolant flow.


water flow within motor  



The water enters at point A. It flows through the water jacket down the length of the motor picking up heat. The flow makes a 180 degree turn (point B) and comes back through a separate channel of the water jacket. At point C, the water flows down the front plate to water channels running in the lower corner of the motor (point D) where it repeats it's journey down the length of the motor (point E) and back (point F). Next, the water flows across the bottom section of the front plate to the right lower section of the motor (point G). The right side cooling system is a mirror image of the left side. After flowing up and down the length of the motor twice more, the water exits at point H.


Photo below of water galleries with sharp edges.


water galleries with sharp edges


We have some concern that the sharp edges where the flow reverses might cause cavitations and suboptimal cooling. Otherwise, the motor's liquid cooling system seems well designed.


Here is the whole vehicle's liquid cooling system layout:

diagram of cooling system  

The coolest water is pumped first to the inverters which are more sensitive to heat than the motors. The water cools the rear motor inverter and then the front motor inverter.

The water then goes to the rear motor and then to the front motor. Finally it returns to the radiator.


At the last race, we had two external sensors reading the outside temperature of the aluminum water pipe (marked A and B). We also recorded the temperatures from inside the motors and inverters.

The coolant is picking up about 5 degrees Celsius in each motor. The coolant starts at air temperature (around 30 Celsius) and reaches 50 Celsius at the end of the race. The motor windings reach 176 Celsius. The inverters reach 64 Celsius.

The radiator was able to drop the coolant temperature about 10 degrees Celsius (sensors out of and into the radiator at points C and D respectively). We found that the coolant temperature rose steadily during the race which indicates that the system was absorbing more heat than the radiator was able to dump.

Therefore we need to increase cooling by the radiator. We decide to increase air flow through the radiator by adding a second high flow radiator fan.


go to two fans on the radiator



More about Electric Motors
back to Lessons Learned menu
cooling the motors -Solid


All content Copyright © 2016 ProEV Inc.,
USA phone (305) 610-6412

Go to ProEV Home