Petroleum electric control system is generally divided into two categories,one is DC (Direct Current) equipment,which used
for driving DC motor,simply SCR(silicon control rectifier)for short. Another is AC (Alternating Current)equipment, which
used for driving AC frequency motor, here called VFD（Variable Frequency Drive) system.
SCR system was designed and developed by ROSSHILL company in the eighties. The oil chain drive equipment was
gradually replaced by the SCR since the stable performance and easy maintenance, that bring the Oil Drilling turn to the full
automation times,comparing with the current emerging Variable frequency system, SCR has the following advantages
1. Mature Technology
SCR equipment has been tested in the field of extreme environment and performed well.
2. Easy Maintenance
SCR came to being earlier, has been used in wider area，for some common problems,generally, engineers with longer
working experience can deal with it, for the complex trouble, need professional serviceman to work out it.
3. Competitive Price
4. The spare parts are available in many district, and could be used universally.
Alternating Current electric control system is the newly-developing drilling Rig Electric Drive System in recent years.
It has earned the good feedback from user for the better performance, higher efficiency and easy operation.Compare with
the SCR system, AC electric control system have the following advantages:
1.Motor Control Mode
Since the Siemens or ABB frequency converter is adopted to drive Alternating Current frequency motor. Having better
working accuracy and stability, especially on winch control, it can easily be lifted and laid down and easy to use, so greatly
meet the use on the drilling site, enhancing the efficiency of drilling, which higher than AC system.
2.Accurate control
VFD system combined with PLC control and Speed measuring machine Variable frequency motor side mounted.These
functions make the motor control achieved the closed-loop control and Run more smoothly,also the running speed can be
controlled according to the actual requirement.
3.Hover Function of winch
Winch is the important part in the rig components, due to the characteristic of the motor itself,the down could not control
by motor, but by its own suspension and auxiliary brake system to participate in the control.since many operating process,
that have high request on the driller. Who having proficiency on operation and problem solved capability , since there is
prone to happen drilling accidents. However,the motor driven variable frequency system with the hover function, made the
winch could stop under control by making the handle which control the motor of winch to return to zero status and without
other auxiliary brake function. Which make the drill’s work simple, safe and reliable. The difference of DC and AC system
in the control of the winch, such as the operation difference between manual gear car and automatic transmission when
operating the car.
4.Highly Integration
With the Frequency conversion rig widely used, according to the requirement of customers, the drilling and mining and
other related data could be collected by PLC integrated into industrial control computer not by a separate instrument, so the
cost could be saved a lot also provide the convenience on equipment install,moving and maintenance.
