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VVVF > MRF-A4

MOTORS FOR OPERATION WITH VOLTAGE AND FREQUENCY CONVERTER (INVERTER) – VVVF TYPE

(VARIABLE VOLTAGE VARIABLE FREQUENCY)

Inverters are electronic devices that regulate frequency and voltage at motor terminals, thereby controlling the magnetic flux and consequently the torque supplied by the motor. They also check the motor’s rotation speed. Additional flywheel masses are not required because the torque is adjusted directly by the inverter in relation to the desired acceleration curve. This type of operation ensures control of the entire operation cycle at every stage for excellent functional comfort. Since the speed is adjusted by the inverter, motors for this application have only one polarity. Drive via an inverter reaches high lift running speeds and short acceleration times; for this reason, the motor is designed to provide high torque during acceleration with relatively low power consumption compared to standard drives at full voltage. The motor can be used for 240 starts/hour without auxiliary force-feed ventilation; however, pre-setting as standard is provided for mounting a fan if particularly severe work or environmental conditions require more intense ventilation. Under rated load and rated voltage and frequency conditions, the motor rotates at a speed between 1410-1440 rpm for 4-pole and 940-954 rpm for 6-pole versions. The A4 build model has a rotation speed for the 4-poles of about 1445-1450 rpm. When choosing a motor, the first item to be taken into consideration in its rated torque. The maximum current absorbed by the motor during acceleration can be roughly calculated using this formula: Imax= (Mmax/Mn)*In; Mmax is the torque requested of the motor by the system during acceleration. MN = rated torque, In = rated current. For acceleration times over 3 sec., the maximum current that the motor is warranted to withstand is 240 starts/hour and must not exceed 2.5 times the rated current. For less than 3 seconds., the engine can be deliver a max. torque of about 2.6 times the rated torque. The breakaway torque and current indicated on the motor plate (MA, IA) are the maximum values that the motor can withstand during acceleration and therefore must not be exceeded. Take these values into account when setting inverter parameters, such as acceleration time.

Product table with main technical data

Three-phase asynchronous motors for drive with inverter – Poles 4 – rpm 1450 – 240 starts/hour – Self-ventilated

Outline drawings

VVVF-MRF 4P Self-ventilated