July 26, 2009

Rectangular flux path motor

Filed under: Articles + Blogs — admin @ 7:12 pm

The electric motor uses more electricity than any other technology.  In the industrial world, it is estimated that 62% of all electricity is used to turn an electric motor.  So it is not surprising that hundreds of millions of dollars have been spent by the Department of Energy and by private companies, in the quest to make electric motors more efficient.

PurePower-150monolithic-magnet-hubs

But improvements in motor technology have always come at a cost.  Magnet improvements have resulted in higher torque density using neodymium-iron-boron magnets in brushless dc and ac induction motors.  Magnet costs have come down substantially over the last few years, but typical induction motors don’t use magnets.  Recent improvements in an induction design use magnetic poles on the rotor to increase torque, but this has to be balanced against the cost constraints of the application.

Lamination steels have seen significant improvement in recent years.  So-called “exotic” alloys have higher saturation flux and produce more torque for the same size motor.  Silicon steels are more efficient and have lower eddy current losses which means less waste heat is generated in the motor and more flux is converted to torque.  But exotic laminations and silicon steel cost more, so again, the gains have to be balanced against the costs.

Tighter machining tolerances can generate smaller air gaps in the motor, which also translates into higher torque output.  But precision machining requires better equipment, and amortizing the cost of equipment into the motor adds cost as well.

So for every improvement there appears to be some cost impact to overcome.  Until now.  For the first time in the electric motor industry, reduced costs and performance improvements come from the same product.

NovaTorque, Inc. in North Highlands California ( sales@novatorque.com or telephone 916 331-8000) has achieved the elusive goal of increasing performance and lowering manufacturing costs in the same motor design.  The outstanding results of this new motor design come from rearranging the magnets and stator to create a rectangular magnetic circuit.  This arrangement eliminates stator back-iron normally used to conduct the magnetic field through the outer ring of the motor.  The magnetic path is shorter and has lower losses than any conventional design currently in production.  Shorter magnetic circuits mean higher torque output for the same size of motor.

Flux-Path-Figure-(Side-View)

Conventional motor laminations are rolled thin so that the bulk magnetizing loss of the steel is minimized.  But transformer steels are more efficient than other lamination steels because there is a favorable grain orientation in the direction of rolling that reduces magnetizing losses in the material by 7 to 8%.  For this reason transformer cores are most often made by using strips of steel organized so that all the material in the core has the grain going in the direction of the core shape.

Grain orientation in an electric motor has never been possible because traditional stator designs always have complex circular paths.  Because the NovaTorque stator is all in straight lines, transformer steel is easy to use.  This makes the stator more efficient, which shows up in higher efficiency over a range of speeds and reduces heat loss.

motor-stator-visiblel

Reduced heating can result in extended operating life, or higher current carrying capability for more demanding applications.  As with other brushless designs, since the stator is on the outside the thermal path is better for cooling the motor.  Heat doesn’t get trapped in the rotor as it would on a brush dc motor.

So the major magnetic and electrical improvements lead to a lot of performance benefits.  But the story doesn’t end here.  The manufacturing process actually lowers the cost of making these motors at the same time.  A real price and performance breakthrough.

The rectangular magnetic circuit arrangement greatly reduces manufacturing costs by using simple straight line stator pole pieces that can be wound individually instead of in a complex circular profile, making the winding process simple and inexpensive.   This method of stator construction is also called the Segmented pole stator.  Segmented pole stators are stators that are wound a single pole piece at a time and then assembled into a stator ring.    This method was introduced by Panasonic FA a few years ago on their brushless servo motors servo motors for electronic assembly machinery.  The manufacturing benefits are substantial.

Winding of a single pole piece is so easy, it can be done on inexpensive “bobbin” winders at high speed and low cost.  This means that much of the capital equipment that is normally associated with electric motor manufacturing is not needed for this design.  Thus, the amortized cost of making a high performance servo motor is largely eliminated and a lot of the process and labor associated with motor manufacturing is reduced as well.

Purepower150-Efficiency

The segmented pole requires no end turn copper at the ends of the stator to jump from phase to phase of the winding, which reduces copper usage by 1/3 or more depending on the design.  End turn copper produces no torque in the motor, so eliminating end turns reduces winding losses and improves efficiency.  This also increases the maximum speed available to the motor designer.

In addition, the space required to accommodate the end turn is eliminated so the motor can be made smaller in axial length.  Less copper also means a lighter weight motor for a given power output.  And in the current economic environment of rising copper costs, eliminating end turns helps keep motors costs down.

Magnet geometry is simple.  By making the magnets triangular, or conical, the straight pole piece easily makes the corners work to huge advantage.  The angle of the air gap can be manipulated to create many different relationships which can be used to leverage the characteristics of different magnet materials.  The triangular air gap path also produces more torque producing area than a comparable motor with a simple cylindrical air gap.

PurePower150-OutputPower

Cumulatively, the materials improvements, the improved copper utilization and reduced magnetic circuit length all work together to produce some astounding results.  Testing shows the motor is more than 90% efficient over 90% of its speed range.  Most electric motors have high efficiency around a small speed range.  A peak efficiency point is not as valuable as a range of high efficiency since as the system operates the on-time at varying speeds will usually produce lower overall efficiency.  The Novatorque technology can have a huge benefit, especially in battery powered systems and hybrid vehicles where efficiency directly impact operating time per charge.

The initial development of the technology was driven by a customer request for a brushless dc motor for a pumping application, but requiring pricing more in line with stepping motors.  After several attempts were made using conventional motor designs, John Petro and Ken Wasson developed the new stator and rotor configuration of the Novatorque motor and with Don Burch, the three set out to create a motor manufacturing company the could deliver the highest possible performance at lower costs than have previously been available.  The company’s engineering team has over 100 man-years of experience in the field of electric motors and is pursuing pilot manufacturing this summer.

Novatorque’s target markets are driven by applications that require outstanding energy efficiency, such as battery powered tools, scooters and electric vehicles, applications that require extreme energy density and small size such as aerospace actuators and down hole equipment, and industrial servo systems where low rotor inertia and high motor power density is valuable in making high speed automation systems that are compact and precise.

(originally published in Design World Magazine July 2008, reproduced with permission)

Digital Position Read-Out

Filed under: Technology Development — admin @ 5:52 pm

dro

This is an actual working prototype hardware that adds Digital Read Out (DRO) capability to conventional woodworking equipment.  This creates dial-in precision to 0.001″ accuracy that is totally repeatable and adds less than $100 Retail Value to the price of the target equipment. Software design of the display allows the unit to switch modes from fractional display 1/4, 1/8, 1/16, 1/32, 1/64 and then reads out in thousandths of an inch.

Slitter

Filed under: Technology Development — admin @ 5:43 pm

power-slitter

General Purpose Power Feeder

Filed under: Intellectual Properties,Technology Development — admin @ 5:39 pm

wood-feed

Simple powered feeder for woodworking equipment.  Concept is targeted to low cost variable speed operation with very compact form.  Can also be used as a powered fence in format with more rollers.

Applications:

  • Table saw
  • Band saw
  • Router

July 17, 2009

Linear Actuator

Filed under: Intellectual Properties,Technology Development — smeyer @ 2:16 pm

alac

Linear actuators are an amalgamation of several different core technologies that are incorporated in a single product.  That’s part of the reason that they are so confusing. The categories of core technologies are motive power, means of transmission, bearing technology, support and feedback.  Not all are always present.  Feedback and support may not be needed if you are doing a hydraulic system that simply opens and closes.

Motive power means electric, pneumatic or hydraulic.  Transmission means how is the power transferred to the load.  In pneumatic and hydraulic systems, there is no means of transmission, because the cylinder and piston actuator that allows pneumatic and hydraulic to operate, is the means of transmission and the bearing system at the same time.  Then there are belt driven designs, lead screw designs, and more recently linear motor designs based on electric motors for input power and control.  But there are also pneumatic and hydraulic systems that do the same things.  So navigating the technology decision is very difficult.

But once in a while, something really different comes along.  Solid Tech has a new solution that minimizes inertia mass, physical mass and system footprint to achieve payload to weight ratios approaching 1 to 1.  Accuracy and power handling capability are parameters of design that can be manipulated for any given application.  The US Patent Office has issued a patent so the technology is available for use.  Check it out.

Contact Steve Meyer at 512 240-5876 or email at stventuresinc@gmail.com