Sprint Electric’s high power field controller optimizes DC drive capabilities

Sprint Electric (www.sprint-electric.com) has expanded its range of DC drives for control of DC motor’s high current excitation fields, with the addition of QLX, a three phase field controller that feature fieldbus options such as DeviceNet, Profibus, ModBus TCP/IP, CanOpen and Ethernet.

The QLX controller works with the armature controller to deliver the required field control functions including field reversal. With currents ranging between 12 Amps and 2250 Amps, the new product utilizes three phase power supply to offer a controlled DC field current. Featuring full digital control and the usual communications facilities, QLX is ideally suited for use in various applications such as in steel handling and hot rolling mill.

With digital functions similar to the company’s PLX range of DC drives, the QLX 3 phase field controller comprise five frame sizes, with up to 2250 Amps current capability. It also offers Field Reversal as well as Auto Field Weakening for high power fields. It also features an integrated Standby Field mode. The QLX interfaces directly with the main armature controller for start and stop functions. The controller cost-effectively includes reversing to big DC motors where the facility exists only with contractors, or when it no longer exists.

Offering a vast array of DC motor control, Sprint Electric has more than 150 models covering both three phase and one phase, non-regenerative and regenerative DC motor applications, which come with digital slip ring motor controllers.

What is a Motor Drive?

Defining a drive can be a bit tricky. Some drives are wholly incorporated into the controller, so that the profile generation takes place in the controller as well as the torque command for the motor. On the other hand, a drive can also refer to the specific power electronic circuitry needed to drive the motor. Electric motors that drive industrial machines need some way to control motor speed. And at its most basic level, a motor drive controls the speed of the motor.

Some manufacturers refer to a controller and motor together as a drive system. However, from the electrical side of things, the drive is often specifically the electrical components that make up the variable frequency inverter itself. So drives are the interface between the control signals and the motor and include power electronic devices such as SCRs (silicon controlled rectifiers), transistors, and thyristors.

Matching the correct drive to the type of motor in an application is critical for getting the best fit for torque, speed, and efficiency. There are a wide range of drives available depending on the needs of the specific application and motor type. In general though, drive types typically fall into two categories; dc and ac drives.

DC drives control dc motors. A basic dc drive is similar in operation to an ac drive in that the drive controls the speed of the motor. For dc motor control, a common method is a thyristor-based control circuit. These circuits consist of a thyristor bridge circuit that rectifies ac into dc for the motor armature. And varying the voltage to the armature controls the motor’s speed.

AC drives
AC drives control ac motors, such as induction motors. These drives are sometimes known as variable frequency drives or inverters. AC drives convert ac to dc and then using a range of different switching techniques generate variable voltage and frequency outputs to drive the motor.

An adjustable speed drive is a general term used sometimes interchangeably with variable speed drive or variable frequency drive. Again, from an electrical perspective, all of these ultimately refer to the frequency converter circuitry.

An ac motor’s speed is determined by the number of poles and the frequency. Thus, as frequency is adjusted the motor’s speed can be controlled as well. A common way to control frequency is by the use of pulse width modulation (or PWM). A PWM drive sends pulsed inputs to a motor and by modulating the pulse width, making it either narrower or wider, increases or decreases the average dc voltage seen by the motor.

Another powerful kind of drive function is known as regenerative braking or regen braking. This is a way of stopping a motor’s rotation by using the same solid-state components that control the motor’s voltage. The energy generated from braking can be channeled back into the ac mains or into filter capacitors. Advantages of regen drives include the ability to run a motor in either forward or reverse direction without having to physically switch the polarity of the motor leads and without the need for reversing contactors or switches.

Mentor MP Variable Speed DC Drives from Control Techniques

Minneapolis, MN – Control Techniques™, an Emerson® Industrial Automation company, announces the release of its Mentor MP variable speed digital DC motor drive designed for energy efficient operation, optimal motor performance and enhanced versatility in its system interfacing capabilities and onboard processing power.

Designed for use in a wide range of industries and applications, the Mentor MP accommodates an output current range of 25 to 1,850A with a single module approach. Drives to 210A are available now in 12 and 24-pulse configurations for low harmonics. Mentor MP is the first DC drive to use patent-pending galvanic isolation to provide electrical separation between the power and control circuits in the event of a power-side failure.

Standard features include an external field controller for larger DC motors where the field current can be greater than the controller’s capacity. The controller provides field forcing for high dynamic applications such as very fast reversing (e.g. typical machine tool spindle applications.) Another feature allows reverse jogging control with two-quadrant drives for lower-cost systems that do not require fast reversal. Also standard is a free SmartCard used to simplify drive maintenance and troubleshooting by storing parameters, PLC and motion programs and copying parameters from one drive to another without the need for a stand-alone PC.

Network connectivity includes Modbus RTU, Profibus-DP, DeviceNet, CANopen, Interbus-S, as well as support for the Ethernet protocols: Modbus TCP/IP, Ethernet/IP and EtherCAT. The Mentor MP’s three universal option module slots provide programming flexibility using any combination of 18 option modules available today. These option modules are common across Control Techniques’ AC, DC and Servo drive ranges and include extensions such as additional feedback options, expanded I/O and powerful onboard programmable control.

Communications gateway solutions can also be implemented easily and economically within the drive by installing two or three networking option modules.

SyPTPro-programmable option modules, called SM Applications, can be loaded with application-specific software such as crane control, winder/rewinder, flying shear and other commonly used automation functions. For less demanding applications, SyPTLite software can be used alone for simple PLC ladder programming onboard the drive. This capacity for on-board configuration can often eliminate a stand-alone controller and so reduce system cost. Further option modules can be used to connect with I/O, networking or Ethernet protocols for control and monitoring.

The eco-friendly Mentor MP is currently the only DC systems drive on the market that is RoHS compliant, helping protect the environment at the end of the product lifecycle.

For more information contact Control Techniques at 1-800-893-2321.

www.emersonct.com

Closed-Loop Drives for DC Motors

The Dart Controls digital MD plus Series of closed-loop drives for DC motors up to 2 HP features an isolated 4-20mA input/output signal capability.

Customers get the DC motor drive, 4-20mA input/output, digital display, and relay outputs for pump running and fault alarms all in one economical package. Custom faceplate artwork is available also.

www.dartcontrols.com