vfd - Condition for max torque

My questions are these:

1. 
   

   If say a 3ph motor connected to a mains supply is rated at 1400 rpm with no load at what rpm approximately does it produce its max torque?

   
   



2. 
   

   If the same motor is run with a VFD which is set at output rpm of about 20Hz will it produce a significantly different max torque?

   
   

Thank you in advance

Haris