Over current detected
Current limit setting
Power Supply current
Lower arm IGBT operation
Current limitation reset
Fig. 5-3. Timing chart for current limitation
(b) How to set up
The current limitation setting IO is calculated as follows ;
IO = Vref / Rs
Vref: Standard voltage for current limitation
Rs: Shunt resistor
In setting a current limit, you should allow for Vref variance, Rs resistance variance, and the delay
between the time the over current limitation is detected and the time the IGBT is turned off.
This function is not effective for currents that do not flow forward through the shunt resistor, such as
reflux current and power regenerative current (see Figs. 5-4 and 5-5). In practice, users are
requested to observe and check the output currents (the coil currents of the motor) of the IC.