Obtain the value of actual ripple
speed in rad/s using either of the two methods:
- Use an oscilloscope to
observe motor current waveform to measure the ripple frequency. This can
be done in two ways:
- Through the
IPROPI pin which provides an output proportional to the motor
current.
- Through a current
probe.
The frequency of ripples is observed in Hz on the oscilloscope.
Please consider at least 20 ripples while calculating frequency. Divide
the number of ripples by the time taken for calculating the frequency in
Hz. Convert into rad/s using Equation 11. Please note that this is the recommended
method.
- Use a tachometer to
obtain the motor speed in rpm. Convert the motor speed into ripple speed
using Equation 10. Finally, convert the ripple speed in rpm to ripple
speed in rad/s using Equation 12.
Equation 10.
Equation 11.
Equation 12.
Where NR is the number of ripples per
revolution. Let this value be called OBS_SPEED.