maxon EC motor ironless winding Technology − short and to the point
Program − ECX SPEED − ECX PRIME − EC − EC-max − EC-4pole − with Hall sensors − sensorless − with integrated electronics
Characteristics of the maxon EC motors with ironless winding: − Brushless DC motor (BLDC) − Long service life − Highly efficient − Linear motor characteristics, excellent control properties − Ironless winding system maxon with three phases in the stator − Lowest electrical time constant and low inductance − No detent − Good heat dissipation, high overload capacity − Rotating NdFeB permanent magnet with 1 or 2 pole pairs Characteristics of the maxon ECX SPEED range: − Power optimized, with high speeds up to 120 000 rpm − Robust design − Various types: e.g. short/long, sterilizable − Lowest residual imbalance − Easily configured online − Fast delivery Characteristics of the maxon EC range: − Power-optimized, with high speeds of up to 25,000 rpm − Robust design − Lowest residual imbalance Characteristics of the maxon EC-max range: − attractive price-performance ratio − robust steel casing − speeds of up to 20 000 rpm − rotor with 1 pole pair Characteristics of the maxon ECX PRIME and EC-4pole range: − Highest power density thanks to rotor with 2 pole pairs − Knitted winding system maxon with opti- mised interconnection of the partial wind- ings − Speeds of up to 50 000 rpm − High-quality magnetic return material to reduce eddy current losses − Mechanical time constants below 3 ms − Special version
1 Flange, front 2 Housing 3 Laminated steel stack 4 Winding 5 Permanent magnet 6 Shaft 7 Print with Hall sensors 8 Control magnet
9 Ball bearing 10 Flange, rear
− sterilizable − heavy duty
Electronical commutation Block commutation Rotor position is reported by three in-built Hall sensors. The Hall sensors arranged offset by 120° provide six different signal combina- tions per revolution. The three partial windings are now supplied in six different conducting phases in accordance with the sensor infor- mation. The current and voltage curves are block-shaped. The switching position of each electronic commutation is offset by 30° from the respective torque maximum. Properties of block commutation − Relatively simple and favorably priced electronics − Torque ripple of 14% − Controlled motor start-up − High starting torques and accelerations possible − Servo drives, Start/stop operation − Positioning tasks − The data of the maxon EC motors are determined with block commutation.
Sensorless block commutation The rotor position is determined using the progression of the induced voltage. The electronics evaluate the zero crossing of the induced voltage (EMF) and commute the motor current after a speed dependent pause (30°e after EMF zero crossing). When stalled or at low speed, the voltage signal is too small and the zero crossing can- not be detected precisely. This is why special algorithms are required for starting (similar to stepper motor control). To allow EC motors to be commuted without sensors in a Δ arrangement, a virtual star point is usually created in the electronics. Properties of sensorless commutation − Torque ripple of 14% (block commutation) − No defined start-up − Not suitable for low speeds and for dynamic applications − Continuous operation at higher speeds (Fans, mills, drills)
I II III IV Block commutation Signal sequence diagram for the Hall sensors Conductive phases VI V
Sensorless commutation
EMF
Hall sensor 1 Rotor position
60 120 180 240 300 360
1
1 0 1 0 1 0
Hall sensor 2 Hall sensor 3 Supplied motor voltage (phase to phase)
2
2
EMF
64 Technology – short and to the point The commutation rotor position is identical to the motor shaft position for motors with 1 pole pair. The values of the shaft position are halved for motors with 2 pole pairs. Legend The commutation angle is based on the length of a full commutation sequence (360°e). The length of a commutation interval is therefore 60°e.
+
U U U
1-2
300°
0°
60° 120° 180° 240° 300°
+
3
3
2-3
+
3-1
Diagram applies to phase 1
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