Appliance Design - January 2008 - (Page 36)

MOTORS Axial sensor magnet Radial main motor magnet Type II Rotor Magnetization S A N Zener Clamps Inductive Energy V M S N S C B N N S 15 deg S 45 deg N S g V M N S N BUD Winding Clamps Inductive Energy SOUTH NORTH NORTH c 360 Electrical degrees c Fig. 1. Rotor magnetization and magnetic profile. Fig. 2. Zener clamps and BUD. The magnetic profile created by both axial and radial flux of the rotor is also shown in Fig. 1. The on-chip Hall sensor detects the North, and South magnetic field, which with simple logic turns on the drivers for phases A, B and C. ing 3 additional power FETS and a more complex controller. In the BUD system, the clamping is accomplished through the mutual inductance of the bifilar windings, so the stored energy is transferred to the VM complementary phase (e.g. B  B’). This approach also provides more balanced motor drive, as compared to standard unipolar drive, because 2/3 of the motor phases are being powered as in bipolar Drive technology The motor’s drive technology is called BUD™ (2), which stands for bi-phase unipolar drive. This drive allows the commutation of a multi-phase BLDC motor with three power devices instead of six, yielding a significant cost saving. It is a motor phase switching technology that provides two driven phases, as in a typical bipolar drive motor. However, it accomplishes this with a 3-step unipolar drive sequence instead of the 6-step sequence used for a standard bipolar drive. BUD technology eliminates the need for separate Zener protection and extends the ability to use low cost unipolar drive from motors of a few Watts to approximately 100 Watts without a cost penalty to the control circuit. (See Fig. 2). As one power FET turns off, the stored energy in the motor coil must be discharged. Without a clamp, such as a power Zener or BUD winding, the power FET will be subject to hundreds of Volts and be destroyed. The Zener will avalanche and dissipate the energy. As currents/motors become larger, the Zener cost becomes prohibitive, making bipolar drive a lower cost solution, requir36 applianceDESIGN January 2008 A B c C c A C B VM A B c C c A C B Fig. 3. BUD commutation sequence. www.applianceDESIGN.com http://www.appliancedesign.com

Table of Contents Feed for the Digital Edition of Appliance Design - January 2008

Appliance Design - January 2008 Contents Editorial Shipments/Forecasts News Watch Makers of Commercial Refrigeration Equipment Turn to Variable-Speed Motors to Improve Energy Efficiency. New Motor Design and Control Scheme Makes Brushless Motors More Economically Feasible for a Wider Range of Applications. External Gas Molding, a Relatively New Technique, Solves Many of the Challenges Associated with the Injection Molding of Large Plastic Parts. Plastic Housings Offer Many Benefits: EMI Protection Isn't One of Them. But, New Materials and Techniques are Solving that Problem. Choosing the Optimal Strategy for Effective EMI Shielding Depends on Both Mechanical and Electrical Requirements Ethernet-Enabled Microcontroller Makes Networking Schemes Easier and More Cost Effective to Implement The Ever-Changing Array of Microcontroller Memory Options Makes it Imperative to Keep Abreast of What's Available to Determine the Optimal Choice for an Application. A Vast Range of Components and Finished Products will be Exhibited at the Country's Preeminent HVAC/R Show, AHR Expo, which is Scheduled for Jan. 22-24 in New York. Advertiser's Index Association Report: PRBA

Appliance Design - January 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.