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DC_MotorCalculation

Thread Starter: Karnan   Started: 8/19/2012 12:26 PM   Replies: 2

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  8/19/2012, 12:26 PM
Karnan
Joined 12/16/2011
Last visit: 5/17/2013
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Hai All,

We have one 3 axis+ spindle Boring Machine,The axis are configured with DC Motor with Encoder FeedBack;and having Old non Siemens CNC controller.

The DC motor Data are given below,

Make : General Electric
Type  : Permenent Magnet Motor
rpm   : 1725 
V      : 48
A      : 3.9 DC
Ambient temp : 40*C

We suppose to retrofit this machine, Any one please tell me how i will calculate the AC Servomotor with Above DC Motor data ??

Thanks&Regards,
Raj
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  8/20/2012, 11:17 PM
Deputy
Joined 8/8/2011
Last visit: 5/20/2013
Posts: 120
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Hello Karnan,

The following would be a close approximation. 
To be more exact would need to know more of the characteristics of the dc motor such as armature resistance.

Power = V * I = 48 V * 3.9 A = 187.2 Watts

Power (kW) = 0.187 kW = Torque (Nm) * RPM / 9550

Solving for Torque (Nm):

Torque (Nm) = 0.187 * 9550 / RPM
                  
                  = 0.187 * 9550 / 1725

                   = 1.04 Nm

Therefore, as an approximation need an ac servo motor which can supply 1.04 Nm of torque continuously ranging from 0 RPM to at least 1725 rpm.

Deputy
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Thank you for this post from:
Karnan
  8/30/2012, 1:45 PM
Karnan
Joined 12/16/2011
Last visit: 5/17/2013
Posts: 217
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Rated: Outstanding [4 out of 5 / rated 4 time(s)]. (4) 
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Hai Deputy,

Thanks for your Valuable information.

In Nm calculation,you mentioned about armature resistance,I have one more doubt,i have one DC motor with details, V,A,Ohm [The pic of motor nameplate is attatched with this thread].

This Ohm is Armature Resistance ??
If Converting DC Motor to Ac Motor,How we calculate the Nm of AC servo motor with Ohm,V,A??

Thanks&Regards,
Raj

Attachment: pmdc.JPG  (5 Downloads)
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