Brushed DC Motors Technology – short and to the point
The centerpiece of the maxon DC motor is the unique ironless winding, System maxon®. This motor concept has no magnetic detent and low electromagnetic interference. With up to 90% efficiency, it leaves other motor systems in the dust.
Graphite brushes In combination with copper commutators for heavy-duty use. Several tens of millions of cycles have repeatedly been achieved in various applications. Graphite brushes are typically used in the following cases: – In larger motors – Under high current load – For start-stop operation – For reverse operation – For control by a pulsed power stage (PWM) The specific properties of graphite bru- shes can cause so-called interruptions (spikes). These are visible on the commu- tation graph. Despite the high-frequency disturbances caused by the spikes, these motors have become widely used in appli- cations with electronic controllers. It should be noted that the contact resis- tance of graphite brushes changes depen- ding on the load. Mechanical commutation
CLL concept With precious metal commutation, wear and tear of commutators and brushes is primarily caused by sparks. The CLL concept largely suppresses sparking, significantly extending service life. When controlled via a pulsed power stage (PWM), higher no load currents can occur, which may lead to increased motor heating. Additional inductance (chokes) in the motor supply lines helps here.
Precious metal brushes and commutators Our precious metal combination ensures that the low contact resistance remains very constant, even after prolonged stand- still. The motors operate with small startup voltages and extremely low levels of elec- trical interference. Precious metal brushes are typically used in the following cases: – In smaller motors – For continuous operation – Under low current load – For battery-powered applications Compared to other motors, the commuta- tion graph is smooth and continuous. The combination of precious metal brushes and the maxon rotor system results in minimal high-frequency noise, which would other- wise cause significant issues in circuits. The motors require virtually no electrical suppression.
Speed
The maxon winding
High connection resistance − High-ohm windings − Thin wire, many windings − Low startup currents − Motor with low specific speed (speed per volt) The maximum permissible winding temperature is 125°C for high-temperature versions (in exceptional cases up to 155°C), otherwise 100°C or 85°C.
The optimal operating speeds range bet- ween 4,000 and 9,000 rpm, depending on motor size. With certain special versions, speeds of over 20,000 rpm are achievable. Due to physics, a DC motor inherently slows down as the load increases when the voltage remains constant. The wide range of winding variants allows for optimal adap- tation to the desired conditions. At lower speeds, a gearhead combination is often more advantageous than a slow-running motor.
Each motor type is available in numerous winding variants (see the motor data sheets). They have different wire cross- sections and number of windings. This results in the motors having different con- nection resistances. The motor parameters that determine the conversion of electrical to mechanical energy (torque and speed constants) also vary. This allows you to choose the motor that is most appropriate for your specific use case. The wire cross-section and number of windings have the following effect: Low connection resistance − Low-ohm windings − Thick wire, few windings − High startup currents − Motor with high specific speed (speed per volt)
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