Mike,
I am not very sure about that & I don't think so it happens in the application. I am not trying to do the test based on the Cole Hersee contactor. The test specification itself states that it should be 90sec ON,1.5sec OFF. I am looking for the failure mode & how long the motors would last before I see any failure. It's a validation test.
Thanks.
I need to have a conversation with whoever wrote the test spec; they obviously put no thought into this at all, or they don't have a clue about what they are doing!!!!
First, what does 1.5sec Off mean??? No fan motor I have ever seen will begin to coast to a stop in anything like 1.5sec, so in-effect, you are trying to reverse the motor while it is still spun up in the previous rotation.
This causes the motor to draw huge transient start-up currents, likely 3X what it would be if you were starting the motor from a stopped condition. This is an extremely unnatural thing to do to the motor, and likely never happens in an automotive application. In fact, I have never seen a fan motor in a car that turns both directions. I'm guessing that it would take the motor up to 20sec to coast to a stop if it had just the aerodynamic braking of the fan.
So, is this what is really intended?
Second, if the goal is to actually reverse the motor so quickly, then using dynamic braking by shorting the motor (or connecting it to a braking resistor) will stop it faster than just letting it coast to a stop under the influence of aerodynamic braking caused by air against the blades.
That should have been specified as part of the test.
So what are you trying to do to the poor motor???