# Help me for select a AC motor

• posted

Dear all, I'm doing my project in university. My project is to replace a DC drive by a AC drive using inverter. The old DC drive parameters are:

- Power 450kW

- Speed 50 to 1000r/min (so Tn = 4298Nm) (Tn: nominal torque) and the requirements are 250 % during 60 seconds acceleration and a periodical overload of 160 percent during 30 seconds. That means I need a starting torque is 250% nominal torque during 60 seconds. (Ts = 2.5*Ts = 10745Nm)(Ts: starting torque) Now I need to select an asynchronous motor to satisfy these requirements but the problems are:

- The starting torque of AC motor is lesser than DC motor so I must select a AC motor with larger power AC motor : Ts = (1.5-2.5)Tn So I must select AC motor power larger than DC motor to satisfy the starting requirement. I selected : P(AC motor) = 1.5 * P(DC motor) =675kW So in AC drive I have: motor power : P(AC) = 675kW speed 1000r/min Tn(AC) = 1.5 Tn(DC) = 6447Nm Ts(AC) approximates 2*Tn(AC) = 12894Nm They are my first draft calculations. Am I right? Can you help me? and give me some advise. I have searched on the internet an AC motor like that but I haven't found any motor. If you have any information or help me find a motor like that. Look forward to hearing you soon. Thanks Tong,