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The series motor is an 11" Hitachi ( same as in in Duncan's car in the banner picture). Rated at 10kw but if ran at 90v should be 20kw. Data specs are 55 lb-ft. at 280 amps and 2600 rpm's if at 90 volts. 120v should be about 3500rpm maybe? Duncan has proved the motor can take at least 10x rated

Sepex motor is a Kostov 11" rated at 20kw at 90 volts. Rated speed is 4000 rpm but only 35lb-ft of torque. 55 lb-ft would require 360 amps and 3500 rpm according to the motor graph. So, while both motors make about the same amount of power, the sepex appears to need more current for the same torque. My Sepex controller only goes to 500 amps peak current which limits motor torque to about 85 lb-ft, according to the motor graph I have. (The motor performance graph is done with If as a percentage of Ia to mimic a series motor)

In a series motor, I understand the current/torque relationship is linear. If 500amps is peak and gives 110 lb-ft torque, for example, That will be my starting and acceleration torque at full throttle till I hit the voltage/rpm limit.

Is this the same linear relationship for the SepEx motor? Is it possible to increase the lower rpm torque to compare with the series motor by increasing the field current?

I like the rpm range of the sepex motor, but the low torque limit will be a problem.