INA138: Current measurement

Tool/software:

Dear All,

I want to use the below schematic to measure current in a 3 Phase inverter - i.e. to measure Phase voltage.

What is wrong in the below schematic. 

1. When I supply DC voltage it provide a correct o/p voltage 

BUT

1. When I provide a 1 micro second pulse it provides a very high o/p voltage. 

How to fix the issue

OR may be I have to fix the issue on how we are sampling the current for measurement ?.

The inverter will be working with 20-25 Khz switching frequency ....

O/P waveform when i provide a 1 microsecond pulse input