Brushed motors

The main benefits of this technology include:

• No cogging torque resulting in smooth positioning and speed control and higher overall effi ciency than other brushed motor types
• Extremely high torque and power in relation to motor size and weight
• Absolute linear relationship between load to speed, current to torque, and voltage to speed
• Very low rotor inertia which results in superior dynamic characteristics for starting and stopping
• Extremely low torque ripple and EMI

FAULHABER DC Motors are built with two different types of commutation systems: precious metal commutation and graphite commutation.

The term precious metal commutation refers to the materials used in the brushes and commutator which consist of high performance precious metal alloys. This type of commutation system is used mainly because of its very small size, very low contact resistance and the very precise commutation signal. This commutation system is particular ly well suited for low current applications such as battery operated devices.

In general, precious metal commutated motors exhibit the best overall performance at continuous duty with a load at or around the point of maximum nominal efficiency.

The term graphite commutation refers to the brush material used in combination with a copper alloy commutator.

This type of commutation system is very robust and is better suited to dynamic high power applications with rapid start / stops or periodic overload conditions.

FAULHABER brushed motors are designed with a variety of different types of magnets to suit the particular performance of the given motor type. These materials include AlNiCo magnets and high performance rare earth types such as SmCo and NdFeB.

The lifetime of a FAULHABER brushed motor depends mainly on the operational duty point and the ambient conditions during operation. The total hours of operation can therefore vary greatly from some hundreds of hours under extreme conditions to over 25 000 hours under optimal conditions. Under typical load conditions a FAULHABER DC motor will have an operational lifetime anywhere between 1 000 to 5 000 hours.

In general the operational lifetime of a FAULHABER brushed motor is limited by the effects of electrical and mechanical wear on the commutator and brushes. The electrical wear (sparking) depends heavily on the electrical load and the motor speed. As the electrical load and speed increase, the typical motor operational lifetime will normally de crease.

The effects of electrical wear are more signifi cant for motors with pre cious metal commutation and vary depending on the nomi nal voltage of the winding. Where necessary FAULHABER DC Motors are therefore fi tted with integrated spark suppression to minimize the negative effects of sparking on the operational lifetime.

The mechanical wear of the commutation system is dependent on the motor speed and will increase with higher speeds. In general, for applications with higher than specified speeds and loads, a longer operational lifetime can be achieved by graphite commutated motors. It is also important not to exceed the load characteristics for the motor bearings given in the data sheet for continuous duty operation.

Doing so will also limit the achievable motor lifetime.

Other effects limiting motor lifetime include ambient conditions like excessive humidity and temperature, excessive vibration and shock, and an incorrect or suboptimal mounting confi guration of the motor in the application.

It is also important to note that the method of driving and controlling the motor will have a large effect on the operational lifetime of the brushed motor. For example, for control using a PWM signal, FAULHABER recommends a minimum frequency of 20 kHz.

FAULHABER specializes in the confi guration of its standard products to fi t the customer application. Available modifications for FAULHABER brushed motors include:

• Many other nominal voltage types
• Motor leads (PTFE and PVC) and connectors
• Confi gurable shaft lengths and second shaft ends
• Modifi ed shaft dimensions and pinion confi gurations such as fl ats, gears, pulley and eccenters
• Modifi cations for extreme high and low temperatureoperation
• Modifi cations for operation in a vacuum (ex. 10-5 Pa)
• Modifi cations for high speed and / or high load appli cations
• Modifi cations for motors with tighter than standard electrical or mechanical tolerances