12
Ip - Iop
Tp = 2.2ln
Ip - Ic
Ic - Amplifier continuous current rating.
Ip - Peak demanded (not amplifier Ip)
Iop - Actual operating current before the peak demand.
Example:
A motor is driven by an
20 - 5
Tp = 2.2ln
20 - 15
4.5.2Dynamic contouring of continuous and peak current limits
Most of the servo motors have reduced continuous current limits at high speeds (Fig. 4.2). This phenomenon is due to commutation limits and iron looses which become significantly high as speed increases and this leads to reduction of the continuous current limit. The ISP amplifiers have the features which enable the user to define the current limit envelope as closely as possible to the motor operating envelope defined by the motor manufacturer.
Velocity
Cont. zone
Interm. zone
Torque
Fig. 4.2:
Typical operating envelope of a brush servo motor
ISP - Rev 6/95
