BIFFI motor Germany BIFFI model BIFFI price

BIFFI motors are a new generation of gear reduction motors, featuring compact size, low noise, maintenance-free operation, and an attractive appearance. The speed ranges from 0.83r/min to 300r/min. This series of low-speed motors is a new high-tech product that integrates electromagnetic drive and reduction mechanisms within the motor housing. The low speed and high torque directly meet customer requirements without the need for additional reduction devices. The motor uses Class B and Class F insulation, with protection ratings of IP44 and IP55, and voltages of 220V and 380V.

BIFFI motor maintenance methods

The radial gap between the motor rotor and stator is called the air gap. Generally, the air gap of a motor is between 0.25-0.8mm. After disassembling the motor and troubleshooting faults, it is essential to align with the original end cover marks during reassembly to prevent rotor-stator rubbing after reassembly. If the noise of brushed or brushless geared hub motors increases, or if gears inside the motor are replaced, all gear tooth surfaces should be fully coated with lubricating grease, typically using No. 3 grease or manufacturer-specified lubricant. Before assembling a brushed motor, check the spring elasticity in the brush holder, ensure there is no friction between the carbon brush and the brush holder, verify that the carbon brush can reach its maximum travel within the holder, and pay attention to the correct positioning of the carbon brush relative to the commutator to avoid jamming or damaging the brush or holder.

BIFFI motor working principle

When three-phase currents are supplied to the three-phase symmetric windings of the permanent magnet synchronous motor stator, the magnetomotive forces (MMF) generated by the currents synthesize into a rotating MMF with constant amplitude. Since its amplitude remains constant, the trajectory of this rotating MMF forms a circle, known as a circular rotating MMF. Its magnitude is exactly 1.5 times the maximum amplitude of the single-phase MMF; F represents the circular rotating MMF, (T・m); Fφl is the maximum amplitude of the single-phase MMF, (T・m); k is the fundamental winding factor; p is the number of pole pairs of the motor; N is the number of series turns per coil; I is the RMS value of the current flowing through the coil. Since the speed of the permanent magnet synchronous motor is always the synchronous speed, the rotor's main magnetic field and the rotating magnetic field generated by the stator's circular rotating MMF remain relatively stationary. The interaction between these two fields creates a resultant magnetic field in the air gap between the stator and rotor. This field interacts with the rotor's main magnetic field, producing an electromagnetic torque Te that either drives or opposes motor rotation; Te is the electromagnetic torque, (N・m); is the power angle, rad; BR is the rotor's main magnetic field, T; Bnet is the resultant air gap magnetic field, T. Depending on the positional relationship between the resultant air gap magnetic field and the rotor's main magnetic field, the permanent magnet synchronous motor can operate in either motor or generator mode. The three operating states of the permanent magnet synchronous motor are shown in Figure 3. When the resultant air gap magnetic field lags behind the rotor's main magnetic field, the generated electromagnetic torque is opposite to the direction of rotor rotation, placing the motor in generator mode. Conversely, when the resultant air gap magnetic field leads the rotor's main magnetic field, the generated electromagnetic torque is in the same direction as the rotor rotation, placing the motor in motor mode. The angle between the rotor's main magnetic field and the resultant air gap magnetic field is called the power angle. A permanent magnet synchronous motor consists of two key components: a multi-pole permanent magnet rotor and a stator with appropriately designed windings. During operation, the rotating multi-pole permanent magnet rotor creates a time-varying magnetic flux in the air gap between the rotor and stator. This flux induces an AC voltage at the terminals of the stator windings, forming the basis for power generation. The permanent magnet synchronous motor discussed here uses a ring-shaped permanent magnet mounted on a ferromagnetic core. Internal permanent magnet synchronous motors are not considered here. Because embedding magnets into a plated ferromagnetic core is very difficult, by using magnets of appropriate thickness (500μm) and high-performance magnetic materials for the rotor and stator cores, the air gap can be made very large (300~500μm) without significant performance loss. This allows the stator windings to occupy space within the air gap, greatly simplifying the manufacturing of permanent magnet synchronous motors.

BIFFI motor working principle

The motor control system mainly consists of a permanent magnet brushless DC motor, DC voltage source, inverter, position sensor, and controller, adopting a "three-phase six-step 120° square wave" drive. The permanent magnet brushless DC motor operates by turning the inverter power transistors on and off according to a specific pattern, causing the stator armature of the motor to generate a magnetomotive force that advances continuously by 60° electrical degrees, thereby driving the rotor to rotate. Under ideal conditions, for the back EMF and current of each armature phase, each power transistor conducts for 120° electrical degrees, with a phase difference of 60° electrical degrees. When power transistors V3 and V4 are conducting, the motor's V and -U (current flowing into the winding is defined as positive direction) are connected. The resultant stator armature MMF is Fa5 as shown in Figure 1; if power transistor V3 turns off and power transistor V5 turns on, the motor's W phase and -U are energized, and the resultant armature MMF becomes Fa5. Fa5 has advanced clockwise by 60° electrical degrees compared to Fa4. Thus, it can be seen that the MMF generated by the stator armature rotates continuously clockwise by 60° electrical degrees as the power transistors switch on and off in a regular sequence. There are six possible switching combination states for the inverter power transistors. Each switching combination state must correspond to a specific rotor position or back EMF waveform to produce the maximum average electromagnetic torque. The interaction force is greatest when the angle between the two MMF vectors is 90°. Since the MMF generated by the electronic armature advances by 60° electrical degrees, the angle between the rotor MMF and stator MMF must vary within the range of 60° to 120° in each switching mode to produce the maximum average electromagnetic torque. As shown in Figure 1, suppose at time t1, the rotor's Fj is located in the plane of coils U and X, causing the rotor to rotate clockwise. At this point, power transistors V5 and V4 should be turned on, making the angle between the stator's resultant MMF Fa5 and Fj equal to 120°. The rotor rotates clockwise under the electromagnetic torque generated by the interaction between Fa5 and Fj. At time t3, the angle between Fa5 and Fj becomes 60°. At this point, power transistor V4 is turned off, and power transistor V6 is turned on. The stator's resultant MMF becomes Fa6, forming an angle of 120° with Fj. The electromagnetic torque produced by both further rotates the rotor. Based on steady-state models, scalar control means the AC motor initially operates in an uncontrolled manner. Its control functions are limited to switching on and off, and in some cases, auxiliary starting, braking, and reversing. To meet certain variable speed drive requirements, some controls with poorer performance emerged, such as voltage reduction speed control for squirrel-cage asynchronous motors, rotor resistance insertion speed control for wound-rotor asynchronous motors, electromagnetic slip clutch speed control, cascade speed control for wound-rotor asynchronous motors, variable voltage variable frequency (VVVF) speed control for squirrel-cage asynchronous motors (VVVF), pole-changing speed control, and variable voltage variable frequency speed control for synchronous motors. Among these speed control methods, except for variable voltage variable frequency speed control, most are open-loop controls that do not require inverters. While the equipment is simple, efficiency is low and performance is poor. Slip frequency closed-loop control based on constant voltage-to-frequency ratio control for squirrel-cage asynchronous motors offers relatively better performance. However, since they are all based on steady-state models, their dynamic performance is poor, and they are generally only used for energy-saving speed control and general speed control applications with low dynamic performance requirements, such as water pumps and fans. Vector control theory deepens AC motor control from external macroscopic steady-state control to transient control of the internal electromagnetic processes of the motor. This has led to a qualitative leap in the control performance of permanent magnet synchronous motors. The most essential feature of vector control is transforming the complex, coupled, non-linear variables inside the AC motor into DC variables (such as current, flux linkage, voltage, etc.) in a stationary reference frame through coordinate transformation. From this, constraints are identified to obtain the optimal control strategy for a specific target.

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