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3) A permanent magnet brushed DC machine is used to drive a geared mechanism in an aerospace valve actuator. The machine in an aerospace grade brushed DC motor manufactured by Maxon(www.maxonmotor.com). The motor is part of their RE Programme range of high performance machines as has part number DC_PART_NO. The specification for this machine contains all the information you need to answer these questions (take care over units). a) Calculate the total friction and drag torque at the no-load speed (i.e. when there is no external load applied to the machine). b) Starting from the equivalent circuit parameters, calculate the no-load speed taking into account the friction and drag torque calculated in part (a) and compare this with the value in the specification sheet. c) Plot the torque (y-axis) versus speed (x-axis) characteristic for this machine design at its nominal voltage, taking care to include calculations of any key operating points (Note this will not match exactly the experimental measurements in the published specification, but should be closeish). d) Using the value of the maximum continuous current for the machine (also referred to as the nominal current in the specification sheet), calculate the machine torque and speed when drawing this current. e) The machine is connected to a simple one-quadrant DC chopper which is switching at 30kHz .Calculate the on-time of the chopper switch if the same torque as part (d) is to be produced at half the calculated speed of part (d)

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