In the subsection of section Classification of electric bikes we looked at options for motors used in electric bicycles, their positive and negative sides.

Let’s try to analyze and compare the characteristics of electric motors (bldc hub motor and bldc stepper motor)from one well-known manufacturers: Leaf Motor (China).

Leaf Motor produces sets with a motor-wheels, and the other kits that use a chain drive.
The analysis will be based on data from well-known owners of electric bikes site EValbum, the characteristics of the manufacturer, and other sources on the Internet. Therefore all figures are approximate, and the findings are an expression of opinion ePowerBikes.ru

As stated by bldc hub motor, voltage motor-wheel independent maximum speed:24V – 25 km / h, 36V – 32 km / h, 48 V – 50 km / h. These data are confirmed by practical measurements elektrovelosipedistov. The maximum velocity at the start line set bldc stepper with 42 km / h and end with 120 km / h. Those cyclists who speed up to 30 miles is enough, can choose a motor-wheel 24V,36V,or 48V.

For practical information, electric bikes with a motor-wheel 36V 500W and lithium-phosphate battery 10Ach a maximum speed of 32 km / h and can cover a distance of 50 km. For those who want to ‘fly’ at speeds above 50 km / h, suitable set of Leafmotor 601kit-1 48V 1000W e bike kit.

Compare sets with the same maximum speed – 45 km / h – a new set 601kit-1 48V 1000W bldc hub motor and bldc stepper 48V 500W. Based on the characteristics of graphs,we choose the rate at which engines operate most efficiently, it is 40 km / h for both.

For the same power consumption in this mode – 420-440 watts, at the time of bldc stepper motor is a little more, but this is neglected. It turns out that energy costs are the same at a speed of 40 km / h. We obtain a theoretical figure 10.5 Wh / km, although in practice the number is likely to be greater. Now suppose that we face a steep hill. The maximum torque developed HBL hub motor – 30 Nm, bldc stepper motor – 38 Nm.

For the calculation we use a calculator elektrovelosipedista. Let Curb weight of a bicycle with the stepper motor – 100 kg, the rise of 7% of 3.5 km. To overcome this recovery time is needed more than 26 Nm on the wheel 26. ” Power expended by the motor-wheels 601kit-1 e bike kit is more than 1060 W at a speed of 35 km / h. Total energy costs – 106 Wh.

What makes it with bldc stepper-kit? He switched to the lowest gear, increasing time and decreasing the rate of 2.4 times (for cassettes with a maximum star 34t). At 2600 revs / min, torque on the shaft of the gearbox – 11 lb lost by power – 390 watts, speed – 14.5 km / h. Cost of energy to overcome lift – 94 Wh. Switching gears allow the rider to use the bldc stepper with the maximum efficiency of ~ 83% versus 73% for motor-wheels 601kit-1. As you know, the availability of transmission system for a bicycle greatly expands the range of effective use of a set of bldc stepper motor. These are one of the best available right now,s o if your´re looking for one, check it out. 9-14 cassette on the wheel 26 “will change the torque of 6 to 60 Nm and a speed in the range of 11.5-45 km / h (about 2100-2900 revs / min) at an efficiency of above 80% (included efficiency gearbox and chain drive). Efficiency of the motor-wheels 601kit-1 has a maximum value of 78% of torque 10-16 Nm.

It is logical that upon arrival at the ideal surface Bonneville Salt Lake in Utah, at 40 km / h, both test sets will spend the same amount of energy. But as soon as the trial will move to an area with hilly terrain, a set of bldc stepper will be more economical than 601kit-1, and of course will be able to overcome the ups who his opponent will not under force.

We note again that the higher efficiency is achieved when using leafmotor’s bldc stepper motor in the range of maximum efficiency, extended thanks to gear bike.

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.