Motor - General

Drive concepts

There are basically three different drive concepts with different advantages and disadvantages: Front-wheel, mid-wheel and rear-wheel motors. An overview of the different drive concepts can be found on the page Special-E.de.

If you would also like to take a look at the mid-engines, you can read the article ‚The big e-bike motor comparison - 13 e-MTB motors in the test‚ from September 2023.

Stromer

Stromer uses 'brushless DC motors', or brushless DC motors (BLDC). BLDC is a marketing term for Three-phase machineswhich draw the AC voltage required for their operation from an electronic circuit that is connected to DC voltage is supplied. In contrast to a simple Direct current machine with carbon brushes is a Three-phase synchronous machine with excitement through Permanent magnets. The three-phase winding is controlled by a suitable circuit in such a way that it generates a traveling magnetic field which pulls the permanently excited rotor along. The control behavior is largely similar to a DC shunt-wound machine.

Sensors

Hall sensors: As shown in the diagram above, position sensors, so-called Hall sensors, are required to control the BLCD motor. There are three of them with the following tasks:

• Feedback: The Hall sensors provide feedback to the controller, which enables precise control and regulation of the motor.
• Position detection: Hall sensors detect the position of the rotor in the motor based on the magnetic field generated by the rotor.
• Commutation: The information provided by the Hall sensors is used by the controller to activate the correct windings of the stator. Activating the correct windings generates a magnetic field that causes the rotor to turn.
• Speed detection: The Hall sensors can also be used to determine the speed of the motor by counting the number of Hall signals per time period.

Temperature sensor: A thermistor is used to protect the motor from overheating. A thermistor (short for Thermal resistor) is a temperature-dependent electrical resistance whose resistance value changes greatly depending on the temperature. There are two types:

1. NTC thermistor (Negative Temperature Coefficient): The resistance decreases as the temperature rises.
2. PTC thermistor (Positive Temperature Coefficient): The resistance increases as the temperature rises.

Stromer uses an NTC thermistor. The protective function of the motor is activated at approx. 135-140 °C. The power is first reduced and support is stopped at 150 °C until the temperature value has fallen below the critical threshold again.

Components used:

• Hall sensor: Honeywell SS461R
• Thermistor: NTC, 10 kΩ (25 °C and Beta value ~3500) - 15 kΩ
• MOSFET (power semiconductor) on the controller:
  For example ST1x, ASI controller:
  10 pieces 1290 BV6319 | 2 pieces 1290 BV6U11
  
  A possible replacement is an IRFB4110, for example:
  - N-Channel FET
  - VDSS of 100V (min. 80 V)
  - RDS on, as low as possible <10 mΩ
  - Diode over DS
  - I max. >100A
  - Housing TO220

The controllers are heavy, the newer ASI models are no longer repairable as the power electronics are potted.

Defects

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