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,
Those calculations may hold true for a AC motor set up for Hz/V mode how

thanh.tong wrote:
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,

Those calculations may hold true for a AC motor set up for Hz/V mode how
ever, using them in Vector or Flux vector mode yields a lot of starting
torque that is controlled very well..

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