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Tracing the Steps of the First Industrial Stepping Motor

06 Feb 2014
Paul Coughlin

There has been a lot of discussion over the years as to who created the stepping motor, or at least the industrial 1.8° motor we know today. The two relevant companies involved with the design were Superior Electric, originally in Bristol Connecticut, and Sigma Instruments, originally in Braintree, Massachusetts. Although Superior Electric seems to have the leading edge as being the first, it appears that Sigma Instruments may have been the true innovator.

In 1952 the General Electric Company designed a stepping motor to be used with the Superior Electric variable transformers and rheostats. General Electric originally sold the motors to Superior, to attach to the rheostats, and Superior sold a complete system back to GE.

General Electric sold the stepping motor design to Superior Electric and in the 1960s Superior improved the design and introduced the M Series hybrid stepping motors in 1970. These were marketed under the name Slo-Syn.

However, in 1952 Sigma Instruments introduced the Cyclonome Stepping Motor, which is regarded as the first practical two-wire stepping motor. Unfortunately it would be years later before integrated circuit electronics would allow for wide spread application use.The Series 9 Cyclonome stepping motors were single phase, uni-directional stepping motors with step angles of 15° (24 steps/revolution) and 18° (20 steps/revolution). Torque ranges were 1 - 12 oz-in.

Cyclonome Step Motors
Cyclonome 9 Series Stepping Motors
Shortly after, Sigma released the Series 18 AC Synchronous motor. These were two phase, bi-directional permanent magnet motors with speeds of 360, 450, 600 and 900 rpm at 120 Vac, 60Hz. Torque ranges were 0.6 – 11 oz-in.

18 Series AC Synchronus
18 Series AC Synchronous Motors

In 1969 Sigma introduced the 20 Series stepping motor, which had solid broached rotor segments and is closer to the typical 1.8° (200 steps/revolution) stepping motor we know today. The 21 Series motor, with laminated rotor segments, was introduced shortly afterward. The laminated rotor segments allowed for cooler, high speed performance and the 21 Series motor became known as the High Performance Motor.

In 1984 Sigma took a giant leap in innovation and created the Enhanced Stepping Motor. This was a revolutionary design in that we placed magnets within the stator teeth, thereby concentrating the flux field, and providing up to 50% more low speed torque. This was released as the 802 Series motors.

Sigmax Technology

Sigmax Technology Enhanced Motors

Along the way Sigma released Bipolar Chopper Drives with patented features such as Mid-Range Instability Compensation and 4-Phase Chopping circuitry which combined the best of recirculating and non-recirculating current regulation.

In 1987 Sigma Instruments was sold to Pacific Scientific, to complement their AC Servo Motors and Permanent Magnet DC Motors with the Stepping Motors. Since then other innovations have taken place for the Sigma Instruments motors, such as the Powermax, Powerpac and CT Series Stepping Motors, but that's for another day.

Kollmorgen now owns and manufactures both the original Sigma Instruments and Superior Electric 1.8°. Internally we (I) still argue as to who released first (eh-hem, Sigma!), but as a team of rivals, we offer the best in the industry.

One last note about Sigma Instruments, Inc. which I share with my Superior colleagues - Sigma invented the Boston Whaler. Ok, not really, but here's the connection: Included with the stepping motors being manufactured in Braintree, MA in 1977, Sigma Instruments manufactured power supplies, solid state and reed relays, sewing machines, outdoor lighting controls and capacitor switching devices. The outdoor lighting controls and capacitor switching devices were part of a division called Fisher-Pierce.

Dick Fisher, of Fisher-Pierce, invented the Boston Whaler while at Sigma. The Boston Whaler is a fiberglass flat-bottom boat, which was widely regarded as being unsinkable. These were used by the Navy Seals in Viet Nam and more popularly seen with Bud and Sandy in the popular 1960s Flipper films and TV series.

Sigma 1977

About the Author

Paul Coughlin

Paul Coughlin - Author

Paul started his career at Sigma Instruments, Inc., one of the original stepper motor manufactures. Through his career Paul has worked for Pacific Scientific Motors & Controls and the various companies acquired by Danaher such as Superior Electric, American Precision Industries (API), InMotion and Kollmorgen. Paul has held numerous positions throughout his career such as Application Engineer, Stepper Product Specialist, International Sales Engineer, Level 2 Systems Application Engineer and is currently the CS Systems Engineer Team Lead.

Paul has worked many motion technologies, but still enjoys working with and talking about stepper motors. If you want to step through something with Paul, contact him here: Paul Coughlin

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