Brief Introduction of DC Brushless Motor：
The electronically commutated motor are the characterized especially by their favorable torque characteristics 、high power、extremely broad speed range and of cause by their unsurpassed service life.
Principles of operation
The differences between a DC motor having a mechanical commutation system and a BLDC motor are mainly found in:
- The product concept
- The commutation of phase currents.
From the user’s point of view, DC brushless motors follow the same equations as those with brushes: torque is proportional to current, speed depends on the voltage and the load torque.
The commutation of brushless motors
In the conventional DC motor commutation takes place mechanically through the commutator-and-brush system. In a BLDC motor, commutation is done by electronic means. In that case the instantaneous rotor position must be known in order to determine the phases to be energized.
The angular rotor position can be known by:
- Using a position sensor (Hall sensor, optical encoder, resolver)
- Electronically analyzing the back-EMF of a non-energized winding. This is called sensorless commutation.
Use of Hall sensors
In general, BLDC motor have three phase windings. The easiest way is to power two of them at a time, using Hall sensors to know the rotor position. A simple logic allows for optimal energizing of the phases as a function of rotor position, just like the commutator and brushes are doing in the conventional DC motor.
Use of an encoder or resolver
The rotor position may also be known by use of an encoder or resolver. Commutation may be done very simply, similar to the procedure with Hall sensors, or it may be more complex by modulating sinusoidal currents in the three phases. This is called vector control, and its advantage is to provide a torque ripple of theoretically zero, as well as a high resolution for precise positioning.
Use of Back-EMF analysis
A third option requiring no position sensor is the use of a particular electronic circuit. The motor has only three hook-up wires, the three phase windings are connected in either triangle or star. In the latter case, resistors must be used to generate a zero reference voltage. With this solution the motor includes no sensors or electronic components and it is therefore highly insensitive to hostile environments. For applications such as hand-held tools, where the cable is constantly moved, the fact of just three wires is another advantage.
Loss calculation of BLDC motors:
It follows the same equations as the DC motor using mechanical commutation except that parameters like iron losses and losses in the drive circuit are no longer negligible in applications where efficiency is of prime importance.
Iron losses
They depend on speed and motor poles， in the torque formula, may be introduced as viscous friction. The equation for useful motor torque becomes:
Mm = k·lm – kv·ω-Mf
Mm= Motor useful torque
k = Torque constant
lm = Motor current
kv = Viscous coefficient for iron losses
ω = Angular velocity
Mf = Bearing friction
Ptr = Ph +Pec + Pe
Ptr： Iron losses
Ph: Hysteresis losses
Pec： Eddy current losses
Pe： Additional losses
The iron loss is proportional to the square of the magnetic field intensity, and the iron loss is proportional to the 1.3-1.5 power of the frequency。 Frequency = Speed *Poles’ pair/60
Losses in the electronics
The current and voltage required by the motor and the drive circuit to be operated at the desired speed and torque depend also on the drive circuit. As an example, a driver bridge in bipolar technique will reduce the voltage available at the motor terminals by about 1.7V, and the total current must include the consumption of the circuitry.
Remember:
- For commutation, position sensors are necessary when operating in incremental mode
- Sensorless commutation is recommended only for applications running at constant speed and load such as fan applications.
Indications Of Motor Data
1: Nominal Voltage ( Unit )： V
Nominal voltage is the applied voltage between powered phases in block commutation. All nominal data refer to this voltage. Lower and higher voltage are permissible, provided that limits are not exceeded.
2： Nominal Torque ( Unit )： N.m
Nominal Torque is the torque generated for operation at nominal voltage and nominal current at a motor temperature of 25°C。 It is at the limit of the motor's continue operation range. Higher torques heat up the winding too much.
3： Nominal Speed ( Unit )： rpm
Nominal speed is the speed set for operation at nominal voltage and nominal torque at a motor temperature of 25°C.
4： Torque constant ( Unit )：N.m/A
This may also be referred to as specific torque and represents the quotient from generated torque and applicable current.
Motor Numbering Information
FL 28 CBL A 38 - 24V - 50 10 A - IE
① ② ③ ④ ⑤ ⑥ ⑦ ⑧ ⑨
①: Frame Size：28mm
②: Brushless Motors with Low cost
③: Series
④: Motor Length：38mm
⑤: Rated Voltage：24V
⑥: Rated Speed：5000rpm
⑦: Rated Power：10W
⑧: Single Shaft(A)、 Double Shaft (B)
⑨: Integrated driver
DC Brushless series motors
We have complete size series from 22mm to 125mm and power range of 1W to 1500W
Out-rotor DC Brushless series motors
Because the rotor is on the outside, the output torque of the motor will be larger than the inner rotor in the same volume. This kind of motor is small in size and light in weight, but its output torque is large. Size range : 20mm – 90mm Power range : 1W – 190W
Slotless DC Brushless series motors
Iron core without slot, small torque fluctuation, smooth operation, low iron loss, high operation efficiency, low heating, suitable for high-speed operation applications.
Size range : 16mm – 49mm Power range : 1W – 500W
Low cost DC Brushless series motors
Referring to the structure design of brushless motor, brushless motor electromagnetic design is adopted to produce low cost brushless motor. Based on the excellent characteristics of brushless motor, the cost of motor is effectively optimized. Size range : 24mm – 48mm Power range : 1W – 60W
Integrated DC Brushless series motors
The motor can be easily controlled with integrated driver but small volume 、light weight and driver port output.
Gearbox DC Brushless series motors
Precision and transmission gearboxes are optional; planetary gearboxes and spur gearboxes are optional; different carrying capacity and deceleration ratio are optional; straight and helical teeth are optional. Also can be designed and manufactured with customized request