Do electronic devices like a servo motor need a certification to be sold in the US market?
The US system is rather different than the EU one. In the EU, CE marking is required, but, for many products, no independent testing is required. A CE mark is a claim, by the party placing goods on the EU market, that the goods comply with the applicable directives. Many of those directives, though, offer the option of having testing performed to particular standards by particular authorized testing laboratories. The party placing the goods on the market, however, is often at liberty to base the marking on its own testing or analysis.
In the States, &quot;UL&quot; is not legally required, although &quot;listing&quot; or &quot;labelling&quot; may be. There are numerous &quot;nationally recognized testing laboratories&quot;, as well as other agencies that are accepted by various local authorities. The former are granted that status by the US Dept. of Labor, as the requirement is for equipment in workplaces. In some jurisdictions, &quot;listing&quot; or &quot;labelling&quot; may be required other than in workplaces.
The same is true in Canada with the Provincial Dept of Labour, if an exemption is needed for experimental work without CSA/UL approval. There is a small fee per unit in field prototypes exposed to the public at large,  but is not needed for private lab R&amp;D.
If you have no internal AC powered circuits or high voltage output and use external approved sources, you are ok to be exempt from UL requirements. Given that some servos use high voltage outputs, the onus is on the integrator who may sell their system to ensure it meets all safety and EMC requirements.
If your competition is someone like &quot;OrientalMotor&quot; note they have many products registered for safety. We don't have any specs for your concept!
So you better start collecting info for filing before volume shipments in case your customers  don't have a good customs broker.

Abstract: World K Series RoHS-Compliant Induction Motors 1W / 3W 6W Features ; Optimal for Uni-Directional Continuous Operation Induction motors are optimal for uni-directional continuous operation such as a conveyor system. Safety Standards and CE Marking Standards 15 W UL 1004 UL 2111 CSA C22.2 No.100 CSA C22.2 No.77 Certification Body UL Standards File No. E64199 E64199 (1 W6 W Type) E64197 (15 W150 W Type) EN 60950-1 EN 60034-1 EN 60034-5 IEC 60664-1 Conform to EN/IEC Standards ...

http://www.orientalmotor.com/products/pdfs/2009-2010/G/usa_info_approved.pdf