Festool C12 EC-TEC manual EC-TECMotor Technology, Electronics

Technical Review of

the C12 EC-TEC

Cordless Drill

By Rick Christopherson

Once again, Festool has shattered the expectations of the drill industry with the release of the new

C12 cordless drill. The C12 is not just a cosmetic change made to an existing design. The C12 is packed with revolutionary motor and control technology on several levels. Festool didn't just leap forward in one area of this drill; they made huge leaps forward in ALL areas of this drill. From the motor, to the electronics, to the geartrain; this drill raised the bar just past the fingertips of the competition.

EC-TEC®Motor Technology

The heart of the C12 is the revolutionary EC-TEC brushless motor. This isn't just your run-of-the- mill motor. This is a permanent magnet, remotely commutated, 3-phase, AC motor. This is the same type of motor used as servo motors in robotic systems where high torque, high speed, and extreme durability are crucial.

So just how unique is this motor? Well, if you mechanically turned the motor, it would generate

a3-phase, sinusoidal AC output; just like industrial diesel-electric generators do. (Do not attempt this.1)

For years, the motor technology of cordless tools has not changed. The brushed DC motor has been the staple—albeit inefficient—motor for ages. The brushed motor is simple, compact, and inexpensive, but it suffers from inefficient use of limited battery power. The greatest weakness of the brushed motor is that the electricity to the motor's windings passes through an electrical connection that is constantly changing and moving. Every time you see the brushes spark inside of a brushed motor, it is a waste of energy that is not available for use by the motor.

1Never attempt to manually turn the output shaft of any Festool drill or connect this drill to the output shaft of another drill. The C12's output shaft has a mechanical lock for bit changing and cannot be rotated manually.

To circumvent the losses of the brushed motor, Festool incorporated a brushless DC motor2 into the new C12 drill. The electrical connections to the windings are permanent, and don't suffer from the inefficiencies of constantly

connecting and disconnecting as the motor rotates.

The brushless DC motor lasts longer, and requires no maintenance, as compared to the brushed motor. It is also smoother and quieter.

Electronics

There are some popular brand drills on the market that are known to destroy themselves under a normal, but heavy load. I know this first-hand because I "smoked" a couple drills during my investigation of drills (including the most expensive drill my local home center carried).

A powerful drill is of little value if it is easily damaged. The C12 has an intelligent electronic controller that not only powers the motor, but more importantly, monitors its health. Unlike other drills on the market, the C12 won't let you destroy the drill (or the battery) no matter how hard you try.

It took less that 30 seconds to destroy a $270, 18- volt drill, yet the 12-volt C12 handled the same

2Even though this is a 3-phase, AC motor; it is the electronic industry's practice to refer to this as a brushless DC (BLDC) motor because the AC power signal is electronically created and controlled from a DC (battery) power source.

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