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Chapter 7

SELECTING OPTIMAL MOTOR AND

INVERTER CAPACITIES

This chapter provides you with information about the inverter output torque characteristics, selection procedure,

and equations for calculating capacities to help you select optimal motor and inverter models. It also helps you

select braking resistors.

Contents

7.1 Selecting Motors and Inverters ................................................................................................................... 7-1

7.1.1 Motor output torque characteristics..................................................................................................... 7-1

7.1.2 Selection procedure............................................................................................................................. 7-4

7.1.3 Equations for selections ...................................................................................................................... 7-7

7.1.3.1 Load torque during constant speed running ................................................................................ 7-7

[ 1 ] General equation ......................................................................................................................... 7-7

[ 2 ] Obtaining the required force F .................................................................................................... 7-7

7.1.3.2 Acceleration and deceleration time calculation........................................................................... 7-8

[ 1 ] Calculation of moment of inertia................................................................................................. 7-8

[ 2 ] Calculation of the acceleration time.......................................................................................... 7-10

[ 3 ] Calculation of the deceleration time.......................................................................................... 7-10

7.1.3.3 Heat energy calculation of braking resistor............................................................................... 7-11

[ 1 ] Calculation of regenerative energy............................................................................................ 7-11

7.1.3.4 Calculating the RMS rating of the motor .................................................................................. 7-12

7.2 Selecting a Braking Resistor ..................................................................................................................... 7-13

7.2.1 Selection procedure........................................................................................................................... 7-13

7.2.2 Notes on selection ............................................................................................................................. 7-13