Drives and Motor Controllers

A motor controller is a device or group of devices that serves to govern, in a predetermined manner, the performance of an electric motor. A motor controller may include a manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and faults.

Every electric motor must have some kind of controller. The motor controller will have differing features and complexity depending on the task the motor will be performing.
 
The simplest case is a switch to connect a motor to a power source, such as in small appliances or power tools. The switch may be manually operated, may be a relay, or a contactor connected to some form of sensor that can automatically start and stop the motor. The switch may have several positions to select different connections of the motor. This may allow reduced-voltage starting of the motor, reversing control or selection of multiple speeds. Overload and overcurrent protection may be omitted in very small motor controllers which rely on the supplying circuit to have overcurrent protection. Small motors may have built-in overload devices to automatically open the circuit on overload. Larger motors have a protective overload relay or temperature sensing relay included in the controller and fuses or circuit breakers for overcurrent protection. An automatic motor controller may also include limit switches or other devices to protect the driven machinery.
 
More complex motor controllers may be used to accurately control the speed and torque of the connected motor (or motors) and may be part of closed loop control systems for precise positioning of a driven machine. For example, a numerically controlled lathe will accurately position the cutting tool according to a preprogrammed profile and compensate for varying load conditions and perturbing forces to maintain tool position.

Select one of the tabs above to learn more about your particular drive technology.

Servo Drive

A servo drive is a special electronic amplifier used to power electric servo motors. It monitors feedback signals from the motor and continually adjusts for deviation from expected behavior.

Function
A servo drive receives a command signal from a control system, amplifies the signal, and transmits electric current to a servo motor in order to produce motion proportional to the command signal. Typically, the command signal represents a desired velocity, but can also represent a desired torque or position. A velocity sensor attached to the servo motor reports the motor's actual velocity back to the servo drive. The servo drive then compares the actual motor velocity with the commanded motor velocity and alters the voltage frequency to the motor so as to correct for any error in the velocity.

In a properly configured system, the servo motor rotates at a velocity that very closely approximates the velocity signal being received by the servo drive from the control system. Several parameters, such as stiffness (also known as proportional gain), damping (also known as derivative gain), and feedback gain, can be adjusted to achieve this desired performance. The process of adjusting these parameters is called tuning.
 
Although many servomotors require a drive specific to that particular motor brand or model, many drives are now available that are compatible with a wide variety of motors.

Alternate names for Servo drives could be: Brushless Servo Drive, AC Servo Drive, DC Servo Drive, Amp Drive, Amplifier, Linear Electrical Servo Drive, Hydraulic Servo Drive, Analog Servo Drive, Digital Servo Drive, Trapezoidal Servo Drive, Sinusoidal Servo Drive, AC Feedback Drive

REA Technologies is an expert in servo drive repair. Below is a list of Servo Drive manufacturers that we are familiar with. If yours is not listed, please call us, we will be able to help you.

Spindle Drives

Spindle Drives are highly reliable AC vector controlled inverter drives. These drives are designed for controlling high speed, and compact AC motors used in machine tool spindle drive applications.

Machine tool spindle drives require one of the most demanding motion solutions.
Ripple or velocity errors leave their mark, literally, on the work pieces being machined.

Repairing damaged spindle drives is one of REA Technologies' specialties.

Some other names for Spindle drives are Asynchronous Spindle Drive, Synchronous Spindle Drive, AC Spindle Drive, DC Spindle Drive, Brushless Spindle Drive, Torque Drive

REA Technologies is an expert in spindle drive repair. Below is a list of Spindle Drive manufacturers that we are familiar with. If yours is not listed, please call us, we will be able to help you.

Soft Start Drives

A motor soft starter is a device used with AC electric motors to temporarily reduce the load and torque in the powertrain of the motor during startup. This reduces the mechanical stress on the motor and shaft, as well as the electrodynamic stresses on the attached power cables and electrical distribution network. A soft start drive can extend the lifespan of the motor system.
 
Motor soft starters can consist of mechanical or electrical devices, or a combination of both. Mechanical soft starters include clutches and several types of couplings using fluid, magnetic forces, or steel shot to transmit torque, similar to other forms of torque limiter. Electrical soft starters can be any control system that reduces the torque by temporarily reducing the voltage or current input. It my also be a device that temporarily alters how the motor is connected in the electric circuit.
 
Electrical soft starters can use solid state devices to control the current flow, and therefore, the voltage applied to the motor. They can be connected in series with the line voltage applied to the motor, or can be connected inside the delta (Δ) loop of a delta-connected motor, which controls the voltage applied to each winding. Solid state soft starters can control one or more phases of the voltage applied to the induction motor with the best results achieved by three-phase control. Typically, the voltage is controlled by reverse-parallel-connected silicon-controlled rectifiers (thyristors), however in some circumstances, with a three-phase control, the control elements can be a reverse-parallel-connected SCR and diode.

Below is a list of Soft Start Drive manufacturers that we are familiar with. If yours is not listed, please call us, we will be able to help you.

Vector Drives

Phase vector drives (or simply vector drives) are an improvement over variable frequency drives (VFDs) in that they separate the calculations of magnetizing current and torque generating current. These quantities are represented by phase vectors and are combined to produce the driving phase vector which in turn is decomposed into the driving components of the output stage. These calculations require a fast microprocessor, typically a DSP device.

Unlike a VFD, a vector drive is a closed loop system. It takes feedback on rotor position and phase currents. Rotor position can be obtained through an encoder, but is often sensed by the reverse EMF generated on the motor leads.

In some configurations, a vector drive may be able to generate full rated motor torque at zero speed.

Some alternate names for vector drives include: AC Vector Drive, DC Vector Drive, Open Loop Vector Drive, Closed Loop Vector Drive, Sensorless Vector Drive

REA Technologies is an expert in vector drive repair. Below is a list of Vector Drive manufacturers that we are familiar with. If yours is not listed, please call us, we will be able to help you.

Inverter Drives

Solid-state inverters have no moving parts and are used in a wide range of applications, from small switching power supplies in computers, to large electric utility high-voltage direct current applications that transport bulk power. Inverters are commonly used to supply AC power from DC sources such as solar panels or batteries.
 
There are two main types of inverter. The output of a modified sine wave inverter is similar to a square wave output except that the output goes to zero volts for a time before switching positive or negative. It is simple and low cost (~$0.10USD/Watt) and is compatible with most electronic devices, except for sensitive or specialized equipment, for example certain laser printers. A pure sine wave inverter produces a nearly perfect sine wave output (<3% total harmonic distortion) that is essentially the same as utility-supplied grid power. Thus, it is compatible with all AC electronic devices. This is the type used in grid-tie inverters. Its design is more complex, and costs 5 or 10 times more per unit power (~$0.50 to $1.00USD/Watt). The electrical inverter is a high-power electronic oscillator. It is so named because early mechanical AC to DC converters were made to work in reverse, and thus were "inverted", to convert DC to AC.

The inverter performs the opposite function of a rectifier.

Some common alternate names for Inverters are: Variable Frequency Drive (VFD), Adjustable Frequency Drive (AFD), Variable Voltage Variable Frequency Drive (VVVFD), Single Phase Variable Frequency Drive, Frequency Drive, AC Drive, Variable Speed Drive (VSD), Adjustable Speed Drive (ASD), Synchronous Drive, Asynchronous Drive, Continously Variable Transmission Drive (CVT), Eddy Current Drive, Regenerative Variable Frequency Drive, AC Induction Drive, AC Pole Number Control Drive

REA Technologies is an expert in Inverter drive repair. Below is a list of Soft Start Drive manufacturers that we are familiar with. If yours is not listed, please call us, we will be able to help you.

DC Drives

A DC drive is a motor control unit that controls a DC motor. DC drives consist of an SCR (Silicon Controlled Rectifier) bridge, which converts incoming three or single-phase AC volts to DC volts.  Using this conversion process, DC drives can regulate speed, torque, voltage and current conditions of the DC motor. This is ideal for industrial processes such as tube mills, extruders, mixers, paper machines and various other controlled applications.

Some common alternate names for DC Drives are: Brushless DC Drive, Linear Drive, DC Servo Drive, PWM Drive, BEMF Drive, Voltage Control Drive, 3 Phase DC Drive, Analog DC Drive, Digital DC Drive

Below is a list of DC Drive manufacturers that we are familiar with. If yours is not listed, please call us, we will be able to help you.

Stepper Drives

A Stepper drive is a special type of motor controller that contains feedback technology to allow it to control the discrete movement of a Stepper Motor.

Some alternate names for Stepper Drives include: Stepper Motor Drive, Half Step Drive, Bipolar Stepper Drive, Unipolar Stepper Drive, Micro-stepping Drive

REA Technologies is an expert in stepper drive repair. Below is a list of Stepper Drive manufacturers that we are familiar with. If yours is not listed, please call us, we will be able to help you.