... /2250DB, ZJ50/3150DB, ZJ70/4500DB, ZJ90/5850DB electromechanical drilling rig model: ZJ40/2250LDB, ZJ50/3150LDB, ZJ70/4500LDB ... speed regulation, so as to gain excellent drilling performance. The drilling rig driven by AC variable frequency motor employs ... an eddy current brake or EATON brake, which improves drilling efficiency, saves energy, increases control capability, improves reliability, ...