# Induction motor scalar control

I have been developing a software for scalar control of three phase induction motor with squirrel cage rotor. This control method is based on voltage-frequency characteristics of the motor. The used motor nameplate contains 400V, 50 Hz and the stator is in wye connection. Based on these values I expect that the slope of the voltage-frequency characteristics will be $K_1 = \frac{(\sqrt(2)*400)}{(\sqrt(3)*50)} = 6.5\,V/Hz$. The problem is that I would like to rotate the motor at 60 Hz. Based on the above given voltage-frequency characteristics the operating point would be in the field weakening region. I had an idea that I can prevent the field weakening of the motor by changing the slope of the voltage-frequency characteristics $K_2 = \frac{(\sqrt(2)*400)}{\sqrt(3)*60)} = 5.4\,V/Hz$ i.e. the nominal stator volatge would be achieved at 60 Hz and not at 50 Hz (please see the attached graph). Is it possible or is this idea wrong? (I see that below the 60 Hz the magnetic flux of the motor will be lower than the nominal value. But the motor starts with no load and the load torque is applied as soon as the motor achieve the no load speed.) Thanks for any ideas.

• Practically your motor will never deliver the nominal torque, but Tnom/1.2 even at 50Hz, because the flux is weakened at all range. – Marko Buršič Oct 24 '17 at 11:15
• But it will deliver nominal torque at 60 Hz or not? – Steve Oct 24 '17 at 12:22
• No, it will never. – Marko Buršič Oct 24 '17 at 18:04