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RHC-1400 SCR

    The National Oilwell Varco (NOV) Ross Hill RHC-1400 is our most popular SCR drive system. Several thousand RHC-1400 SCR bridges are powering drilling equipment around the world. These bridges are on large and small land rigs and numerous drilling platforms. SCR systems usually consist of three, four or five of these bridges depending on the size of the rig.


    These units can be installed in an SCR Power Control House for the portability required by land drilling operations. Some offshore platforms use an SCR Power Control House or install the SCR line up in the rig package. The RHC-1400 SCR cubicle is designed as a front access system minimizing the amount of valuable space the SCR system requires.


    This system design, like all NOV products, focuses on simplistic operation, reliability, superior performance and ease of maintenance.





  • 1600 AF and 2000 AF stationary mount molded case switch, with UV trip and auxiliary contacts
  • Ammeter 0-2000 ADC
  • Voltmeter 0-1000 VDC
  • SCR "ON" indicating lamp
  • 6-Pulse, 1800/2200 ADC, 750 VDC vertical air cooled bridges. Each bridge is protected with two 600 A SCR fuses per SCR. On each pair of fuses there is a micro switch that is opened to indicate the fuses have opened. This switch also takes the SCR bridge off line.
  • A surge suppression "ON" lamp. Surge protection is provided for each SCR bridge. Surge suppression is provided by a fused set of Metal Oxide Varistors (MOVs). The MOVs clamp any voltage spikes in the bridge that may damage the SCR pucks.
  • Lockout switches for each powered function



    The SCR bridge is controlled by the DC Control Module. The module is compact and virtually trouble free. The need for servicing and troubleshooting the module have been eliminated because the module can be quickly replaced. All modules of a kind are interchangeable.

Each module has a safety feature called zero throttle interlock which will not allow any motor to be powered if assigned with the hand throttle advanced. For specific control module details, refer to the information sheet on DC Control Modules.


    This is a motor brake, designed to slow the drawworks motors and cathead to a preset cathead speed within 10-15 seconds after driller releases the foot throttle. The dynamic brake circuit connects the drawworks motors to a steel grid resistor bank. The energy in the free wheeling DC motors is dissipated in the grid resistor bank. After the braking cycle is completed, the resistor bank is disconnected from the motor and does not interfere with normal drawworks operation.


    Bridges are controlled from the driller's console. The console is located on the drill floor near the drawworks. The console is watertight, constructed with the highest quality stainless steel and is equipped with an air purging valve.

Protective functions built into the bridge circuitry are:

  • SCR bridge over temperature
  • Emergency off (Activated by switch on the driller's console)
  • Shutdown for SCR fuse failure



  • Mud Pumps - (Single or dual motors)
  • Rotary table or Power Swivel
  • Drawworks - (Requires two bridges to power a 2000 HP drawworks, or three bridges to power a 3000 HP drawworks)


  • Series motors require sprocket slip.
  • Shunt motors require field supplies (Active field supplies required when two motors are powered by a bridge).
  • Mud Pump synchronizer available (See sales information sheet).
  • PLC based Drillers console available (See sales information sheet).