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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
a 3-phase, sinusoidal AC output; just like
industrial diesel-electric generators do. (Do not
attempt this.
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)
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.
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Never 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
motor
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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
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Even 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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