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Motor Replacement

Thread Starter: Karnan   Started: 7/30/2012 12:29 PM   Replies: 3

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  7/30/2012, 12:29 PM
Karnan
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Hai All,

In one of our Borirng machine having spindle motor[Induction] with 5.5 KW. If we suppose to change this Induction motor into Servo, 
How can i calculate the Nm of the motor ??
And what are the parameter have to take in account for the conversion from Induction motor to Servo motor ??

Please Anyone Give some Guidance.,

Thanks&Regards,
Raj 
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  7/30/2012, 3:34 PM
Deputy
Joined 8/8/2011
Last visit: 5/18/2013
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Hello Karnan,

More must be known about current motor than 5.5 kW.

Specifically just with respect to the current induction motor, its rated speed must be known.

The following is the relationship for calculating the rated data for a motor whether it is an induction motor or a servo motor.

Rated Power (kW) = Rated Torque (Nm) x Rated Speed (rpm) / 9550

For example assuming Rated Speed = 1500 rpm
-> 5.5 (kW) =   Rated Torque (Nm) x 1500 (rpm) / 9550

-> Rated Torque (Nm) = 5.5 (kW) x 9550 / 1500 (rpm)
    Rated Torque (Nm) = 35 (Nm)

If you refer to the attachment, this is a representative torque vs. speed curve for a typical servo motor.

Key points of data for the attached torque vs. speed curve.

For continuous duty rating (S1 100K) curve defines the continuous duty torque capacity of a servo motor across entire speed range from zero rpm (M0 100K) to rated speed (MN 100K  ) to maximum continous speed where continous torque capacity would be zero (Nm).  The reference to 100K defines the theoretical temperature rise of 100 degrees Kelvin across motor windings.  Reason for this curve being defined with a (M0 100K) to rated speed (MN 100K  ) with (M0 100K) > (MN 100K  ) is that as the continuous operating speed of the motor would rise from zero rom to rated speed and beyond the continuous torque available decreases due to friction (bearings) and stator losses (mainly eddy currents) within the servo motor.  This overall torque vs. speed curve is approximately linear in shape. 

For an induction motor  the torque vs. speed curve for continous duty would be similar at least from zero speed to rated speed except by convention for a constant torque motor the speed vs. torque curve would be flat from zero speed to rated speed.  Above rated speed the continuous torque capacity of the induction motor will reduce rapidly toward zero.  This range of torque vs. speed curve is often referenced as the Constant Power region where below formula would be true at all points within Constant Power region.

Power (killowatt - remains constant) = Torque (Nm - decreases) x Speed (rpm - increases) / 9550  

Deputy

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Thank you for this post from:
Karnan
  7/31/2012, 6:53 AM
Karnan
Joined 12/16/2011
Last visit: 5/17/2013
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Hai Deputy,

Thaks for your Valuable description.
Can you Please give me a guidence to, How can i change the Hydraulic Axis to Servo ??

My Hydraulic Axis Description is 

150 mm Dia.Hydraulic Cylinder
400 mm Stroke

Like to change it into Servomotor with Ballscrew.!! 

Thanks&Regards,
Raj 
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  7/31/2012, 2:43 PM
Deputy
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Last visit: 5/18/2013
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Hello Karnan,

SIZER is the tool that is used to size a motor and associated drive system for a mechanical system such as a ball screw.

You will need to be logged onto service and support website and you can download the current version, which would be SIZER 3.7 and then SIZER 3.7 Hot Fix 1 (which gets installed into a previously installed version of SIZER 3.7).

The below link may work for your computer, but if not perform a search for SIZER on the service and support website.
https://support.automation.siemens.com/WW/llisapi.dll?func=cslib.csinfo&lang=en&siteid=csius&aktprim=0&extranet=standard&objid=10804987&DataKey=10804987&treeLang=en


To provide a path toward possibly achieving a change from hydraulic cyclinder to servo motor and ball screw must have the mechanical data for the system:
 Steady payload to be moved
 Internal mass of transport system
 Ball screw (lead screw) pitch
 Spindle diameter
 Spindle length
 Friction of ball screw
 Efficiency of the spindle drive
 Density of the spindle material
 

After this must define the movement from point A to B (distance and time) then possibly B to C, etc. for duty profile.
In addition if the load changes during parts of move this can be input in the move profile.

Deputy

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