MD_Electrical Electronic Monthly_: The Switch to Switched Reluctance

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The latest information on Electrical & Electronic Components

January 8, 2009

The demand for higher electric-motor efficiency has renewed interest in switched reluctance motors, specifically in areas requiring speed control. The Switch to Switched Reluctance looks at the features that make this motor so interesting, and why it hasn't done more. Then we're Teaching with Toys by exploring some play stuff for kids that has an engineering bent. A pair of special motors offer unique abilities and applications while the last article details how they safely "fly" a cabled high-definition camera across the field of play -- at 60 mph! Our feature content from the web is a switching loss calculator for IHLP inductors, perfect for helping you work out those switching power supply blues, and the usual assortment of new products.

-- Robert Repas, Assoc. Editor

The switch to swtiched reluctance
Teaching with toys
Motor + encoder = fine positioning
A motor pump built for solar power
Safety brake helps put high-def eye in the sky
Online switching loss calculator
New products

Articles

The Switch to Switched Reluctance

Switched-reluctance (SR) motors were developed in the 1800s but, apart from a few embedded-drive applications, they have not been widely applied. Their optimum operation depends on relatively sophisticated switching control, something not economical until the advent of compact but powerful solid-state power devices and ICs. Now, with a new emphasis on energy efficiency, switched-reluctance motors may be ready to take a more prominent role in appliances, industrial equipment, and even off-road gear.

Motor + Encoder = Fine positioning

Put together an encoder equipped with a relatively large-diameter clear aperture and a motor to come up with an Integrated Motor Encoder Assembly with resolution to 0.02 arc-sec. ABEC7-Class ball bearings make the device reliable and extend its service life. Hall-based commutation lets the device work with a variety of standard motion controllers. To limit wobble, the motor/encoder features a tightly toleranced hollow shaft. According to the manufacturer, the device was made to handle high-acceleration point-to-point motion.

A Motor pump built for solar power

Anticipating a sharp spike in interest in solar-powered systems, Engineers at Laing Thermotech Inc. designed the Ecocirc DC pump, a circulation pump that connects directly to photovoltaic cells.
The design is based on a spherical motor, a concept invented by Laing. It consists of a hemispheric rotor and impeller that sits on a hard, wear-resistant ceramic ball. There are no conventional shaft bearings or seals, which eliminates play in the bearings and the resulting noise. The ceramic ball, acting as a self-aligning bearing, is lubed and cooled by the fluid being pumped. And the ball, like all parts exposed to fluid, resists corrosion. The pump does not require regular maintenance, even after lengthy shutdowns, according to the company.

Teaching with toys

A model steam engine or toy workbench won’t guarantee a child will pursue a technical career. On the other hand, it can’t hurt and might be a lot of fun besides. So here are some toys and kits spanning all engineering disciplines, electrical and electronics included, that could spark the imagination and perhaps launch a career.

Safety Brake Helps Put High-Def Eye in the Sky

Next time you watch a major sports event on TV, especially those in high definition, you could be seeing it through the lens of an ActionCam HD camera. ActionCam suspends a camera moving at up to 60 mph over the field of action — and that field can cover a million square feet.

Featured Content

Online Switching Loss Calculator for IHLP Inductors

What's said to be an industry-first, free Web-based tool to compute switching losses for IHLP inductors is now available on the Web site of Vishay Intertechnology, Inc. The switching loss calculator can be customized for individual applications to let designers select the correct part for an optimized board design, while speeding time-to-market. The switching loss calculator is available for buck, boost, and buck/boost dc-to-dc converter topologies.

To compute inductor losses in the past, designers had to complete complicated Steinmetz Equations by hand, a time-consuming process that boosts chances for human error.

Vishay’s loss calculator lets designers simply enter the input and output voltage, frequency, output current, and ambient temperature for their application. With the selection of an inductance value, ranging from 0.1 μH to 10 μH, the calculator immediately provides results for copper, core, and total losses along with the estimated temperature rise of the inductor. The correct Vishay IHLP part number is also displayed for reference.
Vishay Intertechnology, Inc.

New Products

Voltage Regulator on a SIP

The ultralow-profile VR110B080CA-1C voltage regulator has a single 7-Bit DAC programmable output of 0.8375 to 1.6 Vdc, 80-A maximum output current 12-Vdc input voltage, 88% full load efficiency, and is Intel VRM 11.0 compliant.
Murata Power Solutions Inc., Power Electronics Div.

Cable Strain Relief

A hard/soft strain relief eliminates stress and strain from an electrical conductor’s termination points. The cable connection is designed with an antitwist function as well as the elimination of the pistoning action of conductors inside the cable jacket at the termination point of an assembly.
C&M Corp.

Digital Readouts

The ND 200 Series digital readout (DRO) is a single-axis position display that can be integrated into a machine datatransfer network. Included is an ability to design functional equations to manage interconnected operations of multiple axes and soft keys. The units also come with a card for gage hookup.
Heidenhain Corp.

Vision Sensors

The latest addition to the Checker vision sensor line is Checker Model 252. Software sensors verify height, width, and diameter and deliver pass/fail inspection results.
Cognex Corp.

High-Pressure-Resistant Prox Sensors

Series P high-pressure-resistant sensors, for use in high-pressure hydraulic systems, come in different sizes for operating pressures from 1,450 to 7,250 psi. The device’s stainless steel housing is imperviously shrunk onto a ceramic disk at the sensing face.
Contrinex Inc.