For a motor that has a minimum of on/off cycles, a mechanical contactor from allen-bradley.com, squared.com, etc is a frequent choice. A mechanical: adapts well to most temperature environments, generates arcing, has a life based upon cycles.
For a motor that has many on/off cycles, or a motor that is nearby other electronics such as PLCs, PCs, etc; then a solid state contactor is a good choice. These are made by power-io.com, sprecherandschuh.com, etc. A solid state: be aware of temperature rise, has virtually no limit on cycles, switches cleanly at the zero crossing mark (= low electronic noise), can handle momentary inrushes fairly well.
For a motor that you need to vary the speed, then something like a ssddrives.com, abb.com, etc is common. A vsd: be aware of temperature rise, virtually no limit on cycles, has electrical noise concerns, infinite speed adjustability, somewhat costly.
