Photos by Teknatool
Most of the machinery in a typical woodworking shop – planers, jointers, drill presses, and the like – is powered by conventional AC (alternating current) induction motors. Inside the motor housing is a stator – essentially a mass of copper wire (referred to as ‘windings’), which uses electricity to produce a rotating magnetic field that turns a rotor, which in turn drives the machinery we use. Along with the stator is a commutator, armature, and brush assembly.
DVR (Digital Variable Reluctance) motors, also referred to as ‘Smart Motors’, have moved the conventional motor into the postmodern digital age.
Externally a DVR motor looks no different than a conventional motor. But inside you won’t find permanent magnets, brushes, or electrical connections to any moving parts. As well, there is no current flow in the rotor, which means less wear, less heat, and a much longer service life. What you will find inside a DVR motor is a micro-processor that constantly monitors motor load and adjusts power to accommodate the changing load status – it can increase and decrease motor seed (RPMs) depending on the load. This results in energy savings that can be as high as 50 percent over a conventional motor. The micro-processor can also store information on different speed settings and switch from one speed to another with the press of a button.
Another significant advantage of a DVR motor is that it can accommodate a wide range of motor speeds, from as low as 50 RPM through to 100,000 RPM. Because the DVR motor is mounted directly to the drive shaft there is no need for belts or pulleys, and the associated loss in power due to friction, vibration and heat. DVR motors also feature Electro Magnetic Boost, which enables the motor to produce the highest torque at the lowest speed, and more constant torque over a wide range of speeds.
The DVR motor has electronic braking that enables the machine to rapidly come to a stop without wear or tear on any parts. In the event of a sudden increase in motor load or an abrupt spindle lock, the DVR motor cuts power to the drive shaft instantaneously, significantly reducing the risk of user injury or internal damage to the motor.
Along with infinitely variable speed and continuous torque, these motors operate at the ‘whisper’ level – virtually silent – and vibration-free.
Currently you’ll see 1-3/4 HP and 3 HP DVR motors on drill presses from King Canada, Teknatool (Nova), and Rikon, and a 2.3 HP lathe from Teknatool. Rikon also sells a conversion DVR motor that can be mounted on Rikon’s 14″ band saws (10-324, 10-325, and 10-326).
It will be interesting to see where, and when, DVR motors turn up on other woodworking machinery. Like most new technology, the initial pricing on DVR powered machinery is appreciably higher than on conventional AC machinery. However, if you operate a band saw or lathe over extended periods of time, the energy cost savings, along with longer motor life and operational flexibility that these motors offer, might induce you to become an early adopter.
You may hear the name Striatech over the coming years. They’re a subsidiary of Teknatool (teknatool.com), the company that manufactures and markets the NOVA line of lathes and drill presses. Teknatool is the company that designed the DVR motor, now marketed through Striatech (dvrsmartmotor.com), who will likely be licensing their technology to other woodworking companies in the future.