VSD Variable Speed Drive Controller
Product
Datasheets and Brochures
Technical
White Papers
Product Overview and Features
Lufkin Automation offers the ultimate in beam pump
control. The Lufkin Well Manager with a Variable Speed Drive
(VSD) is a packaged system that matches pumping to reservoir
conditions, eliminating shut downs. Instead of traditional on/off
cycling to match well performance, the system keeps the well pumped
down by continually adjusting pump speed—stroke by stroke.
Horsepower ratings from 10 to 150 are available. The Lufkin Well
Manager provides a variable analog output voltage as a speed control
input to the VSD. The control algorithm optimizes pumping
speed based on either downhole pump fillage or surface card setpoint.
Speed is adjusted as often as once per pump cycle to keep the well
pumped down.
Ideal for environments where your well can't be shut
down.
- Sanding/pump sticking problems
- Heavy crude production
- Steam flood operations
- Situations where shutting down would adversely affect production operations
- Speed changes without replacing sheaves
By slowing the unit just enough to avoid working
load violations, this system can also help you manage rod float
problems and peak rod load issues with heavy oil. And if the Lufkin
Well Manager detects any other pumping equipment malfunction, you
can choose to stop the well or continue running at a programmed
minimum speed. VSD control and safety features in the Lufkin Well
Manager fully optimize production even within the mechanical limits
imposed by difficult pumping applications.
VSD-Specific Features
Configuration flexibility. The VSD is a
smart rod pump control system that integrates VSD and rod pump
controller. This combination replaces the traditional
contactor box and provides everything in one enclosure.
Factory-tested integration. The Lufkin
combined package of the Lufkin Well Manager and the VSD in the same
cabinet has been fully integrated and tested for compatibility.
The combined package, with enhanced features, provides for simpler
field installation, better service support and an assurance that the
pre-wired, factory-tested cabinet has already addressed any
interference issues.
Simplified setup. Default VSD parameters for
the Beam Pump application in the VSD simplifies setup, because most
parameters are properly defaulted. Only items such as motor
parameters need be entered.
Optional heater kit. For cold climates, the
VSD features a thermostat-controlled heater with fan-bypass
relay.
Optional bypass contactors. With the optional
bypass, the Lufkin unit can detect a drive fault through Modbus
communication or digital input. The user can program the delay
time, and whether or not the unit should switch automatically to
normal downhole- or surface operation mode and continue
pumping the well at line
frequency, cycling the well on and off at pumpoff. If not, the Lufkin
unit will retry the allowed number of times prior to arriving at a
malfunction state that will require user intervention.
Dynamic braking is not typically needed. When
the gearbox experiences negative torque, the VSD system switches to
torque control to maintain a positive motor torque, thereby allowing
potential regenerative energy to be kept in the pumping unit as
kinetic energy. This allows for a more efficient operation,
since dynamic braking typically would involve the use of a resistor
bank or an expensive regenerative inverter.
Connect to existing NEMA D or B Motors. The
VSD can operate an existing induction motor, thereby reducing
installation costs associated with purchasing a new motor. A NEMA B
motor should have somewhat higher average efficiency, but the
initial cost vs. the power savings will likely have a long payout.
Optimized production and pumpdown. Downhole
or surface pump fillage is the basis for controlling speed to
optimize production and pumpdown. The normal speed control
algorithm is based on a programmed starting speed, and increases or
decreases in speed are determined on every stroke from the
dynamometer pump card.
Programmable upstroke/ downstroke speed.
Downstroke speed can be programmed as a percentage change from the
upstroke speed, and the point in the stroke at which the speed
change occurs is also programmable.
Working-load limits for speed limiting. If a
peak or minimum working-load limit is exceeded (e.g., due to
paraffin buildup or low flowline temperatures), the normal pump-fillagespeed
control is overridden, and the speed is reduced in steps. On each
stroke that a violation occurs, the speed is slowed an additional
increment, until the violation no longer occurs. In this manner,
production is optimized within the mechanical load limits
established by the operator.
Stop on malfunction or run at minimum speed.
If any of the safety limit violations occur, the operator has the
option to continue operating at minimum speed or to stop the pump.
Because of sanding or thermal issues, however, stopping may not be
an option. When stopped or running at minimum speed, the unit
is placed in a downtime state for the programmed downtime period.
When that period expires, the unit will attempt to start up
normally.
Rod-float mitigation. The rod-float
mitigation feature provides options for minimizing or eliminating
rod float on wells that experience this phenomenon.
- RFM Torque
Curve (patent pending). The most effective method is
the RFM Torque-Curve option which becomes active when the rod
load drops below a programmed threshold. It utilizes an
advanced RFM Torque Curve which guides the VSD on the
downstroke. This minimizes the amount of speed drop needed
to mitigate the rod-float condition, thereby optimizing
production.
- Fixed torque level. The second choice
is a fixed torque level on the downstroke, somewhat less
effective than the RFM Torque Curve.
- Preset speed.
The third option is to reduce the speed to a preset level
when rod float is detected-the least effective method since
speed changes are filtered by programmed deceleration times.
Peak-power limiting (programmable peak torque).
In a steam-flood or steam-cyclic operation, the well cools with
time, and the peak load and peak power increase with time. The
unit can be programmed with an overall peak torque limit to protect
equipment (e.g., from thermal motor overloads) and keep it operating
within the limits of the system.
Convenient Modbus master programming and monitoring.
A keypad and LCD give the operator a way to program and monitor VSD
via the Lufkin unit which is capable of Modbus master communications,
using RS-485.This has been customized for the Lufkin VSD application
so that all normal drive programming can be accomplished through the
keypad, or via host, thereby providing a unified interface.
Parameter comparison checking
between unit and VSD. Additional tools are provided to verify the
consistency of the VSD drive parameters with those stored in the Lufkin
Well Manager and to copy the parameters from one device to the
other, should an inconsistency be found.
Speed plot for 24 hours (1
minute sampling). Speed changes during the day can be viewed with
the 24-hour speed plot to view production optimization
effectiveness.
Technical Specifications >>
