They are intended to drive the main outfits of the drilling rig (drawworks, rotary table and mud pumps) and to supply the auxiliary users (asynchronous motors 0.37...75 kW, normal lighting, safety lighting).
The driving of the main outfits is provided depending on the type of drilling rig, by 4...8 d.c. motors, with powers of 550 or 850 kW, fed by thyristor converters.
The supply of the motor with controllable voltage, from thyrstor converters is made with through an electric switching circuit diagram, which provides d.c., curent distribution and higher operating reliability.
The electric equipment operating in areas with explosive potential has a suitable design according to IEC standards. It can be designed to operate in geographical areas with temperate or tropical climate or with low temperatures of -40º C, at different standardized voltages and frequencies of 50 or 60 Hz.
The equipments are provided with heating, ventilation and air conditioning systems which are meant to ensure their operating capacity under these geographical areas.
The normal protection degree ensured by the electrical equipment frames is IP44 or IP54 according to IEC, excepting for the ventilation holes.
Within the electrical driving system, the representative equipment is the control and regulation station type SCR, which makes the conversion of the electrical energy by means of the power semiconductors. The cabinets with electric equipment within the SCR stations are placed in thermally insulated containers, drilling type, provided with ventilation or air conditioning unit. The SCR station external connections are realized by cables provided with withdrawable sing-pole couplings for the power circuits and by cables with multicontact couplings for the circuits of controls.
A higher operating reliability is provided by an electronic control system and a system for the thyristor converter testing. If the drawworks and the mud pumps are driven by 2(3) d.c. motors mechanically coupled on the same shaft, the electronic control blocks provide rotor current balancing.
Function of the electric energy source, there are available two electric driving systems:
The supplier can also deliver the electric cables for interconnections (power and control cables) cut at suitable lengths, provided with terminals, marked and labeled in accordance with the general arrangement diagram of the drilling rig.
The electric cables may be delivered together with the prefabricated modular supports which setup the "cables base supports", finding into an arrangement corresponding to the drilling rig.
The equipments are delivered into a package suitable for the railway / maritime transport, excepting for the containers which should be protected and secured all the time of transport.
The equipments are delivered fully tested on the specialized testing stands of the supplier; the user is to perform only the electric connections at the mounting side.
The supplier should also deliver all the accessories required for mounting, the first necessity spare parts for operating during the guarantee time period as well as spare parts for 2(3) years of operation.
The supplier also should provide the technical assistance for mounting, putting into operation and services, after the quarantee time has expired.
