Most of the machines with such applications require less maintenance due to SR motors, while these are expensive, but aren't they more reliable and better than the other kinds of motors ? So why aren't they prefered over other kinds of motors for such applications ?
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\$\begingroup\$ Didn't you already say they are expensive? \$\endgroup\$– PlasmaHHSep 12, 2016 at 9:16
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\$\begingroup\$ Yes, But I would assume most of the machines they are used on, get them for long term , and since they require low maintenance and have a higher uptime, it easily has a higher benefit over the other options. \$\endgroup\$– SherbySep 12, 2016 at 9:18
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\$\begingroup\$ When I google "SR motor", I get a Wikipedia article about switched-reluctance motors. Is that what you're referring to? It says that a big drawback is high torque ripple, which would be an obvious problem in any heavy-duty application. Did you not look this up before asking here? \$\endgroup\$– Dave TweedSep 12, 2016 at 10:46
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2 Answers
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Switched reluctance motors require electronic circuitry to do the switching, so they don't have more than a century of history behind them like commutated DC motors, induction motors and wound-rotor synchronous motors. Preferences are always heavily influenced by experience. Also, the need for an electronic controller makes them less attractive for constant-speed operation in applications now served by induction motors.
You have not defined "heavy load" or "heavy duty." Electric motor torque and power ratings span about 8 orders of magnitude. Where in the range between cell-phone vibrator and steel mill does "heavy duty" fall?
The cost of SR motors will probably come down as manufacturing volume increases. However the cost of the motor and controller are not the only cost issues. There is also the cost of making the expected service life of the driven equipment as long as the expected life of the motor.
With volume manufacturing, SR motors can probably be competitive with induction motors in equipment cost, efficiency and all aspects of performance for applications requireing speed control. However, they may not be competitive over the entire power range of induction plus wound-field synchronous motors. It may only be a matter of time.
Update
A leading electric machine researcher has recently expressed serious doubts about the future of switched reluctance machines:
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Mostly they are a new form of motor design and the technology has to mature. One important note of SR motors is they have torque ripple, this effect can be minimized or eliminated dependent upon the geometry of reluctance paths.
They require control circuitry like BLDC motors, however the control design is less complicated. Depending upon geometry, SR can (and probably will) require more uController pins to control it.
Dyson (the vacuum company) is starting to use this technology.
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\$\begingroup\$ They were actually one of the 1st motor designs. The 1st motor that Faraday span was a switched reluctance motor. They however did not show any practical usage until power electronics were created \$\endgroup\$– user16222Sep 23, 2016 at 16:46
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\$\begingroup\$ @JonRB It is easy to find descriptions of Michael Faraday's homopolar motors. I don't think they can be considered to be switched reluctance motors. Is there another Faraday motor that I have not found? \$\endgroup\$– user80875Sep 25, 2016 at 16:15