The stator flux linkage in one phase of an AC machine is given by y = No sin cot. Based on this equation show why it is necessary to operate a variable speed drive with a constant Volts-per-Hertz characteristic over most of the speed range. [5 marks] (b) An induction motor drive has the following components. 3-phase induction motor 3-phase diode rectifier 3-phase inverter DC link capacitor PWM system 3-phase modulation signal generator Constant Volts-per-Hertz block Draw a block diagram of the drive system showing how these components interact and clearly label all signals. [10 marks]