Synchronous and BLDC motor are AC powered motor is AC power supply by 50 weeks and turn. BLDC motor is the stator into the alternating current, a rotating magnetic field, and the rotor magnetic field generated by the sensor, so that two magnetic field, along with the rotor and the stator rotating magnetic field rotation. Which slow the rotor than the stator rotating magnetic field, there is a deterioration of sync so called asynchronous machine. The hub motor stators with the BLDC motor, the rotor is formed artificially by adding the same DC magnetic field, so that the rotor on the stator rotating magnetic field along with the simultaneous turn before said hub motor. BLDC motor is simple, low cost, easy to install, use and maintenance. So widely used. Disadvantage and low efficiency, low power factor on the grid negative. The hub motor is a capacitive load, high efficiency, can improve the power factor, multi-purpose large-scale mining did not prepare.
hub motor and the BLDC motor stator windings are the same, the main difference is that the rotor structure. hub motor’s rotor with DC excitation windings, so they need external excitation power, the introduction of current through the slip ring; the BLDC motor’s rotor is short-circuited winding, the current generated by electromagnetic induction. In contrast, hub motor is more complex, high cost.
Uses: hub motor generators are mostly used in large-scale applications. The BLDC motor is used in almost all motor applications. hub motor can be flexible and adjust the input side of the excitation voltage and current phase, that is, the power factor; BLDC motor power factor is not adjustable, generally between 0.75-0.85, so in some large factories, BLDC motor used more often, you can attach a hub motor to do tune cameras, used to adjust the factory interface with the grid power factor. However, the hub motor, high cost and maintenance workload, compensation is now generally use capacitive power factor.
Comparison of motor start-up mode
1 Direct start: by the power capacity limit
2 series reactor startup: starting torque is not easy to lead, may be secondary impacts.
3. Autotransformer start: start a buck, there are secondary impacts, adjustable voltage range is limited.
4 soft-start variable resistance: thermal resistance, fluid resistance,
5. Magnetron soft start: adjust the conduction angle of SCR power controller to regulate the flux of change.
Soft-start frequency: AC – DC – AC mode, the voltage can be controlled to become the frequency AC power for high voltage motors.
Motor star delta starter
1 When the load on the motor starting torque is not critical but also limit the motor starting current and the motor to meet the 380V / Δ wiring conditions in order to start using delta method;
2 The method is: when the motor starts the motor connected as a star after a successful connection when the motor starts to divert into a triangular electrical wiring (by double-throw switch quickly switch);
3 due to motor starting current and power supply voltage to provide start-up time is proportional to the current full-voltage start-up current is only 1 / 3, but only full voltage starting torque starting torque for 1 / 3 Star delta starter, is a step-down start it at the expense of power in exchange for reducing the cost of starting current to achieve. It can not be dismissed and the size of the motor power required to determine whether a star delta starter, but also to see what kind of load, generally need to start light load, heavy load operation can still be a star delta starter, under normal circumstances, squirrel-cage motor starting current is 5-7 times the running current, and voltage requirements of the grid is generally plus or minus 10% (I remember) in order not to form the grid voltage is too large so the impact of a star delta starter, the general requirements in squirrel-cage motors power transformer rated power of more than 10% will use star delta starter. Only squirrel-cage motor was a star delta starter.