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# TIDM-1003: The nominal RMS winding current of a motor.

Part Number: TIDM-1003

Dear TI Experts:
I think TIDM-1003 is a valuable reference design.
In the document, I found the following statement for phase current.
"The power stage has to provide a 15-ARMS nominal current to the motor winding"
"Considering an overloading of 200% for startup with a full load, the peak winding current will be 45 A."
"The nominal RMS winding current in a motor is 15 A."
"Thus, with a range of 0 to 3.3 V at the input of the ADC, motor currents of (1.65 ÷ 33) / 0.002 = ±25 A can be measured."
1. The final ±25 A measurement design is related to the peak winding current 45 A, right?
2. Could you kindly show me how to determine the nominal RMS winding current of a motor?
In Table 1 of TIDM-1003 document, we can find the nominal VDC=48V and rated power= 500W. Suppose we have a PMSM motor with known Vbus and rated power, could you kindly show me how to determine the nominal RMS winding current?
Wish you the best!
Happy New Year!
Tang Han
• 1. You are correct, the current feedback for the ADC was designed for +/-25A to account for the motor max current
2. The 15A spec is given as continuous current for the motor in the motor datasheet. 45A is found by multiplying 15 * sqrt(2) * 2 and rounding up to 45.

Sean

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