maxon EC motor iron-cored winding Technology − short and to the point
Program − ECX TORQUE − IDX − ECX FLAT − EC-i − EC flat − with Hall sensors − sensorless − with integrated electronics
Characteristics of the maxon EC motors with iron winding: − Brushless DC motor (BLDC) − Long service life − Comparatively high inertia − Motor characteristics may vary from the strongly linear behaviour − Hall sensor signals utilizable for simple speed and position control − Multipole NdFeB permanent magnet − Smaller commutation steps − Winding with iron core and several teeth per phase in the stator − Low detent torque − Good heat dissipation, high overload capacity Properties of the maxon ECX TORQUE - Programs: − Highly dynamic due to internal, multipole rotor − Mechanical time constants below one millisecond − High torque density − Easily configured online − Fast delivery Properties of the maxon IDX program: − High continuous torque − High power density − IP65-protected design − Easily configured online Characteristics of the maxon EC-i program: − Highly dynamic due to internal, multipole rotor − Mechanical time constants below 3 ms − High torque density − Speeds of up to 15,000 rpm Properties of the maxon ECX-FLAT and EC-flat programs: − Attractive price-performance ratio − High torques due to external, multipole rotor − Excellent heat dissipation at higher speeds thanks to open design − Variants with open rotor or fan for even higher torques − Flat design for when space is limited
1 Flange, front 2 Housing 3 Laminated steel stack 4 Winding 5 Permanent magnet 6 Shaft 7 Print with Hall sensors 8 Ball bearing 9 Spring (bearing preload) 10 Flange, rear
Electronical commutation Block commutation Rotor position is reported by three built-in Hall sensors which deliver six different signal combinations per commutation sequence. The three phases are powered in six differ- ent conducting phases in line with this sensor information. The current and voltage curves are block-shaped. The switching position of every electronic commutation lies symmetrically around the respective torque maximum. Properties of block commutation − Relatively simple and favorably priced electronics − 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 arrange- ment, a virtual star point is usually created in the electronics. Properties of sensorless commutation − No defined start-up − Not suitable for low speeds and for dynamic applications − Continuous operation at higher speeds (Fans, pumps)
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 0 1 0 1 0
1
Hall sensor 2 Hall sensor 3 Supplied motor voltage (phase to phase)
2
2
EMF
+
U U U
66 Technology – short and to the point The values of the shaft position can be calcu- lated from the commutation angle divided by the number of 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.
1-2
300°
0°
60° 120° 180° 240° 300°
+
3
3
2-3
+
3-1
Diagram applies to phase 1
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