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Transcript
MAC DIVISION Asynchronous vector motors INVERTER DRIVE: WHICH MOTOR TO USE WITH? Are you planning to run a marathon in high-heeled shoes? Then, why are you using an standard asynchronous motor in your variable speed application? Reservados todos los derechos por Vascat, S.A. STANDARD MOTOR vs VECTOR MOTOR Design priorities: PARAMETER STANDARD MOTOR VECTOR MOTOR O peration Directly from the mains Inverter duty V/ F ratio Fixed (4 0 0 V/ 5 0 Hz in Europe) Variable, depending on the application The inverter allows different V/ F ratios Power factor Parameter to be maximised It reduces the reactive power consumption It' s not a priority The inverter corrects the reactive power consumption Starting peak current Parameter to be minimised It will determine the protections There' s no starting peak values due Inverter duty Starting torque To be maximised Nominal Torque from 0 rpm' s Inertia Not important It' s not designed to be used in variable speed To be minimised in order to have the best dynamic performances Peak Torque - To be maximised To match the Inverter current limits Cooling system Self cooling system Active Fan cooled The best performances from 0 rpm' s Constant Power Range Not important It' s not designed to be used in variable speed To be maximised Wide working zone in field weakening mode Reservados todos los derechos por Vascat, S.A. CONSTRUCTIVE DETAILS Active Fan cooling system Reinforced materials and vacuum impregnation Low losses laminated square frame Integrated encoder connector Second shaft for encoder fitting Integrated PTC for thermal winding protection Reservados todos los derechos por Vascat, S.A. Parking brake option Low inertia Rotor MOTOR PERFORMANCES: STANDARD vs VECTOR 200 % 160 % 100 % Nm 40 50 70 125 Hz Nominal Overload Standard Vector MAC Q Reservados todos los derechos por Vascat, S.A. . Nominal Overload TYPICAL PROBLEMS USING STANDARD MOTORS FOR INVERTER DUTY Motor warming at low speed operation Standard: Insufficient motor cooling working at low speeds due a self cooling design. Vector: Perfect motor cooling at any speeds thanks to its active fan cooling system. Low Torque performances working beyond the nominal speed Standard: Not designed to work beyond the nominal speed: very limited constant power work. Vector: Wide constant power working area. Very useful in winding applications Poor acceleration response: Problems in dynamic applications Standard: High rotor inertia values. Very poor dynamic performances. Vector: Very good dynamic performances thanks to the optimisation of the rotor design ( Ø/length ratio) Reservados todos los derechos por Vascat, S.A. TYPICAL PROBLEMS USING STANDARD MOTORS FOR INVERTER DUTY High maintenance costs: Limited expected life time Standard: Fast degradation of winding and isolating materials due the high frequency voltage transitions. Vector: Long life time thanks to the reinforced materials and vacuum impregnation. Additional motor modifying costs Standard: Require additional motor manipulation: not prepared to fit a feedback device for close loop operation (encoders, resolvers...), neither active fan cooling system for low speed operation. Vector: Integrated active fan cooling system. Prepared to fit any feedback device. Higher Current consumption and inverter size Standard: It’s not possible to match the motor and application speed performances. There’s only two available winding codes: Start and delta connection. Vector: Each motor can be manufactured with an specific winding code in order to exactly adjust de motor current consumption to the inverter current limits. Reservados todos los derechos por Vascat, S.A. PRICE: STANDARD MOTOR VS VECTOR MOTOR Although the vector motors are more expensive than standard asynchronous motors, this price increment is widely compensated by their technical advantages. In order to perform a right economical comparison between this two motor types, it will be necessary to take into account the total cost of each COMPLETE solution: Additional modifying costs: Feedback and active fan installation. Motor oversizing: Due the poor performances of the standard motors working with inverter duty. Repair costs: Material degradation due to inverter duty work. Inverter price: Vector motors can improve the inverter sizing through the right choice of the winding code Reservados todos los derechos por Vascat, S.A. SECTORS & APPLICATIONS Reservados todos los derechos por Vascat, S.A. CONCLUSIONS Standard asynchronous motors are suitable for fixed speed applications and mains supply, vector motors are suitable for inverter duty and variable speed applications. Main advantages of asynchronous vector motors: No warming problems with low speed operation. Wide constant power working range. High dynamic response: low inertia. High overload capacity. Longer expected life time: repair & maintenance cost savings. No need of motor modifications: Integrated encoder and active fan. Reduction of inverter size: customised windings Dimension savings: high power density Reservados todos los derechos por Vascat, S.A.