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The universal motor, an often maligned old workhorse, is actually a particularly adaptable motor, and still proves very useful in many applications. When an application calls for high starting torque, power, and speed – all combined in a small, lightweight package – the Universal Motor (UM) often emerges as the clear choice. This is especially true for intermittent duty applications. The UM can operate with nearly equivalent performance on both AC and DC power. (for Universal Motor specified details and customized applications see our Customized Motor Application Guide)

Groschopp has, for many years, supplied universal motor components (an armature and field set) to an OEM manufacturer of high quality compact construction machines – in this case a concrete vibrator. The motor, which looks "standard", is actually manufactured to very tight tolerances. The design was upgraded last year to an IPX4 rating (washdown duty).

"The components are installed in a plastic housing, which is strong and lightweight, but its flexibility requires these tight specifications for the armature core laminations, and 100% inspection of the bearing journals," said Stan Spaulding, Product Manager. "In this rugged, high vibration atmosphere we do everything we can to insure that the armature cannot make contact with the field, for both safety and performance considerations."

All 230 volt electrical parts are insulated from any grounded metal parts, since the universal motor must be air cooled and some water ingress is possible. Double insulation helps, and working with the OEM, Groschopp engineers used their experience and design expertise to help develop a venting system which minimizes this potential ingress problem. The design also includes special fiberglass commutator insulation and corrosion‐resistant coatings on the lamination core and shaft.

Another use for the versatile universal motor came when a manufacturer of high performance products needed a motor for their portable hydraulic pumps. They trusted Groschopp to choose the motor, but also, as a partner, to source a special cast housing. A two‐pole UM was optimized for rugged conditions, including creating custom bearings and windings for armature, machining the housing and end bells, and assembling, testing and providing quality assurance for the modules.

"There's actually nothing about the motor that is particularly 'magical' in this application. It's really about the whole product," said Jared Birk, design Engineer. "We have been happy to supply motion technology to this customer for many years, and throughout that time we have grown more and more involved with production of their tools – including design, tooling, vendor selection, and production. They trust us as engineers and business partners to make sure the entire job gets done right."

When the US military needed an impact wrench for their vehicles, their vendor came to Groschopp for the motor. The UM was the perfect fit for the application with a need for a high quality, rugged, and durable tool to withstand the extreme conditions experienced in the Abrahams Tank, Bradlee Fighting Vehicle, and the Humvee. With lives hanging in the balance this impact wrench can't fail. The 30 Frame UM parts set was matched with a new housing from the vendor. The extensive testing to which Groschopp subjected the tool proved the design.

Groschopp's latest project using the UM is powering a heavy duty concrete drill. This motor must work in tough construction situations drilling concrete foundations and the like. This motor is approximately 9 inches in length (plus output shaft and external cooling fan) and 4.6 inches in diameter, and has a continuous 2 HP rating, and up to 3.5 HP peak. It is capable of speeds of up to 20,000 RPM. This motor, supplied with a skeleton frame design, can be used for a quick prototype for testing purposes, and a custom housing can be designed for final assembly. Standard frame sizes can be fitted with application specific housings to accommodate special mounting, so they can be dropped into existing applications.

Despite the fact that the universal motor must have air flow for cooling, it is possible to make this rugged motor relatively resistant to environmental conditions. The IPX4 rating that can be achieved will handle all but the worst of extreme conditions. The high starting torque, high speed, and ruggedness of design make the universal motor the best choice for many construction and maintenance tools. It features an excellent performance to weight ratio, is able to withstand high temperatures, and is a cost‐effective solution.