Thank you all for your responses.
I have googled my heart out trying to research this! I will see if there are any EV motor vendors that I can contact for further help. I have actually contacted a couple of motor manufacturers to obtain performance curves.
Dereck, you have cleared up some of my confusion on what the values represent. As I mentioned before I am following a method for this, the bit where I am stuck at is looking at the performance curves and reading the RPM at which the motor delivers my required hp. From what you have said however, it seems that the rated speed IS the RPM at which the rated horsepower is delivered (from the HP calculation). This is very useful to me. How would you read this from a motors power curve though? I will give an example, the HPEV AC-20 is supposedly a good choice for lightweight vehicles, which mine definitely is. However, at 5hp on the curve the RPM is very low, which of course gives me a very low overall gear ratio. This is where the majority of my confusion has been..
In fact on the "peak" graph above (72 volts / 300 amps) it doesn't even measure 5hp at any point. However on the "continuous" plot for the same motor..
I emailed HPEV and they said their ac motors "want" to run at 6000 RPM. As i said my main confusion is coming from the graphs..
The reason I have a precise limit is because of the method I am following, I am looking for a motor based on the required hp at my design center speed of 30mph. My next calculation is based on the RPM at which this horsepower is delivered, so that I can calculate the overall gear ratio:
overall gear ratio = RPM(motor) / RPM(wheel)
Anymore help to clear this confusion is greatly appreciated!