In case you missed it, electric motors are rapidly replacing air driven handpieces in the dental industry. Although this has long been the standard in Europe we in the US have been slow to change. The primary advantage of the electric motor over air driven is the torque and as a bonus it is much quieter, easing the tension caused by whining air turbines. The down side is of course is the initial cost and the expense of repair.
In the world of electric motor handpieces there are 2 primary technologies, the brush motor (old technology, on the way out) and the Brushless motor most new systems are built with brushless motors they are more reliable and efficient as well as giving more accurate control over speed and torque.
The brush motors operate off of DC current which is applied to carbon brushes that contact a circular commutator which has between 6 and 24 segments each opposing pair of contacts attaches to either end of a coil of wire on the rotor or armature. When the coil is energized it creates a magnetic field which pushes against the opposing force of the stator (usually a fixed magnet or magnets attached to the inside of the case of the motor) which causes the rotor to rotate to the next pair of contacts which energizes another coil and round and round it goes.
You will find brush motors in Lab handpieces, Operatory handpieces, even Implant handpieces. The primary problems you will find are:
Like the brush motor the brushless motor uses a coil of wire which is energized to create a magnetic field that pushes against an opposing field in a permanent magnet. However in the brushless motor the magnet is on the rotor and the coil is fixed. The pulses required to make the rotor go round and round are generated by a Microprocessor instead of brushes contacting a commutator. This is why we say that the brushless motor runs on a commutated signal not a DC voltage. It is also why a brushless motor needs at least 4 wires (conductors) and the brush motor only 2.
As a result of the lack of brushes the brushless motor;
The down sides to the brushless motor are;
Really it just means we have to work together on these to get the best result for the customer. We have tried to distill this down to a few rules of thumb;
When you pick up an electric motor get as much information as you can, here are a few questions to ask.
Try and determine if it is a brush motor (the motor runs on 2 wires is the easy way) and if the control works with other motors then just send the motor. If they do not have an extra motor to run with the control then you may as well send in the control with the motor.
If you can put a straight nosecone with a burr in it and spin the motor you can learn a lot.
The following is a list of the systems we have in house to test handpieces with: