Undervoltage is defined as a condition where the applied voltage drops to 90% of rated voltage, or less, for at least 1 minute. Low-voltage conditions occur when a facility asks for more power than...
The higher the frequency, the faster the motor will spin. This results in better cooling, so the motor can be designed smaller. There are other effects as well, but perhaps this will get you started.
motor magnetizing current will increase with increase in voltage, therefore power
factor of motor will decrease and motor will draw more current than rated.