We have 4 small motors located about 100' away from their motor starters. They are fans on a heat exchanger. The conduit to them runs outside underground to a junction box and into cable tray inside to the control panel. We have a roll of 12/C #10 and we can include a ground wire in the conduit...that seems like it would work ok....just never seen such an installation. I've always seen cables one cable per one motor. Is this a bad design idea?