... ZJ70/4500DZ, ZJ90/5850DZ AC variable-frequency motor drive drilling rig model: ZJ40/2250DB, ZJ50/3150DB, ZJ70/4500DB, ZJ90/5850DB ... electromechanical drilling rig model: ZJ40/2250LDB, ZJ50/3150LDB, ZJ70/4500LDB mechanical drive ... a parallelogram integrated raising design, so the derrick and equipment on the drill floor can be installed at ground level ...