Converting DC motor and Drive to AC motor and drive 1

[ysn]

How do I calculate the toruqe required and the HP required for a DC motor to be replaced with AC motor and Drive. the Dc motor is of 90hp, 1500 rpm drives an extruder.

 

[volvibeguy]

ysn,
Three things determine the torque produced by an AC induction motor;
1= the strength of the magnetic field of the stator
2= the strength of the magnetic field of the rotor
3= the phase angle difference between rotor and stator fields.
There are several formulas for configuring the info you request, try your local electrical parts dealer for a copy of Uglys engineers pocket reference guides,inside you will find several formulas for conversion needs,also Delmars Textbooks are an excellent source for this info, hope this helps.
JB

 

[Farkel]

Is the extruder started loaded or unloaded? What was the starting torque of the DC motor? 90X5250/1500=315ft/pds of torque running. Suppose you are using 50Hz., since the 1500RPM. Some DC motors have high starting torque, higher than their AC equivalents. Most Design B motors, according the MG-1 NEMA have a 150% locked rotor torque or better.

 

[ysn]

Hi Forkel,
thanks for the info, it goves me some idea, how i go about it, the extruder starts at no-load

 

[jbartos]

Suggestion:
Torque in lb.-ft = 90HP x 5250 / 1500RPM = 315 lb-ft
Try Baldor motor:
75HP
460V
60Hz
332 lb-ft Full load torque
1160RPM
1.15 S.F.
1684M Type
16X92 Winding Number
ECP4404T-4 Catalog Number