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How to select your product?

 

DC MOTORS

This range, consisting of motors with and without iron in the rotor, offers all the advantages needed to meet the highest service requirements, such as low power consumption, high performance, small dimensions and high acceleration.

All these engines can be equipped with high-performance gear motors as well as encoders. Associated to electronic speed control, extremely precise servo systems can be obtained.

The following guidelines will help you make your choice:

 

Type

Rotor with iron

  • Great range of speed variation (> 1,000 with control loop)
  • High starting torque, ideal for moving large inertias
  • Superior volume/power ratio to other technologies
  • High performance

Ironless rotor

Ironless DC rotor motors offer the same features as the above in addition to:

  • Very high performance
  • High acceleration capacity thanks to its low rotor inertia
  • Zero reluctance torque
  • Voltage/speed, load/speed and torque/current linearity
  • Highly resistant to overload
  • Weak electrical parasites
  • Low inductance

 

Switching

Graphite brushes and copper commutator

  • Demanding service requirements, for example directional reversal or frequent starts

Precious metal brushes and commutator

  • Low and constant switching resistance
  • Low start voltage
  • Weak parasitic radiation

Capacitor Long Life (CLL) concept

  • Limits sparks and significantly increases switching life in the case of precious metal

 

Service life

In electromechanical switching motors (brushes-commutator) service life is related to the type of application and can vary between 20,000 hours and several tens of hours, if used for extreme applications.

The main determinants are:

  • The current present in the motor
  • Rotation speed
  • Operating cycle
  • Environmental influence

Heating

The maximum permissible temperature in the winding is limited and the current flowing through it is the main heating factor. It is important to limit the average current.

Features

The behavior of a DC motor with permanent magnet can be seen in the following graph:

 

The current (I) depends solely on the winding and is proportional to the load (M).

The speed (n) is linked to these two factors but also varies with voltage (U).

Idle speed is proportional to voltage (IJ).

Within the limits of the maximum characteristics of an engine we can obtain infinite work points.

 

 

BRUSHLESS MOTORS

The technology behind the brushless motor, besides the advantages of a DC motor, also involves those of the AC motor: strong start torque and long service life. Switching the motor phases is performed electronically. Mechanical components such as commutator and brushes are replaced by electronic components.

The motor consists of a 2- or 4-pole magnet in the rotor, plus another magnet to excite the Hall effect sensors. The stator consists of a three- or four-phase winding powered by power electronics that generates the rotating field.

Thanks to the Hall effect sensors we ensure successively feeding the phases, whereby we have the same characteristics as a DC motor.

These electronics can be integrated in the motor, for low power, or in independent external boards.

Brushless motors are used for applications requiring a long service life, high speeds and tough operating conditions.

The following guidelines can help you in your choice:

Type

4-phase

Adapted to the most demanding industrial applications, they can be easily integrated into classic drive applications and servo systems.

Numerous accessories are available upon request (gear motor, brake, encoder, box, IP54, etc.).

3-phase

They are suitable for applications requiring high dynamics features (acceleration, starting torque, etc.)

The use of rare earth magnets gives them their reduced size.

The different accessories that can be adapted to the motor provide the right solution for any servo systems application.

Motors with integrated electronic switching:

This series of compact products is intended for applications where service life, ease of power supply and small size are important criteria.

 

AC MOTORS

The range of AC motors uses synchronous permanent magnet technologies and asynchronous single- or three-phase technologies.

Synchronous motors allow rotating at a constant speed regardless of variations in load and voltage. There are different versions for a single-phase network 12, 24, 48, 100 and 230 V-50 Hz.

Asynchronous motors are characterized by a rotation speed dependent on the load applied. Idle speed is related to the power supply frequency.

AC motors are often used in systems in systems with constant speed and torque, powered directly by the mains voltage. They provide a long service life, necessary in most applications.

The following guidelines can help you in your choice:

Type

Synchronous permanent magnet:

  • Two-winding stator
  • Multipolar magnet rotor with radial magnetization
  • Rotation in both directions by field displacement using auxiliary condenser

Asynchronous squirrel cage:

  • Multi-groove three-winding stator
  • Squirrel-cage rotor
  • Single-phase or three-phase versions

 

Service life

Is related to use and mainly limited by the life of the bearings.

Heating

Synchronous:

  • Convection cooling; the motor can block without risk of damage
  • Class B insulation

Asynchronous:

  • Built-in fan-cooled
  • Class E insulation

Features

The behavior of the motors is described in the curves displayed below. The features vary depending on the heating and precision of the voltage, frequency or capacitor value.



 

STEPPER MOTORS

Stepper motors are an ideal interface between mechanics and control electronics in positioning applications.

In fact, the very nature of the stepper motor means it converts an electronic pulse into a constant elemental increment called a step. Thus, a certain number of pulses provides a displacement of the same number of steps. The design of stepper technology allows a defined number of steps (24, 48 and 200 steps/rev) and the selection of various sizes provides solutions in the most diverse fields of application.

It is primarily intended for open loop positioning systems, i.e., without position feedback components (encoder, sensor...) and for applications requiring high holding torque and high operating reliability.

The following guidelines can help you in your choice:

Type

Hybrid motors

  • Toothed stator
  • Toothed and magnetized rotor
  • Usual number of steps per revolution: 100 or 200
  • Unipolar or bipolar operation
  • High speed, high acceleration
  • Angular precision up to ±3%
  • Possibility of control in steps or microsteps
  • Use of appropriate electronic board

Permanent magnet motors

  • Toothed stator
  • Permanent magnet rotor
  • Number of steps per revolution: 24/48
  • Unipolar or bipolar operation

Linear actuators

Linear actuators fitted with a stepper motor and a mechanical nut-and-bolt system enable obtaining linear displacement proportional to the pulses supplied by the electronic equipment.

Service life

Is related to use and mainly limited by the life of the bearings.

Heating

It is cooled by convection, the motor can be stopped supplying its holding torque without risk of damage.

Insulation

Class B (IP 54). Possibility of IP 55 protection.

Features

 



 

We can see the behavior of stepper motors in the typical curve. This feature varies according to heating, supply voltage, the current in each phase and the operating mode (unipolar or bipolar).

 

ELECTRONICS

In most applications, performing a motorized function requires control electronics. Electronics acts as an interface between external information (sensors, encoder) and the drive (motor, gear motor) to ensure the management of the automatism and protect the motor. Consideration of the globalization of automation and usage parameters is crucial in selecting control electronics perfectly suited to the application.

 

ELECTRONICS FOR DC MOTORS

The main function of electronics for DC motors is to control the speed or torque according to the load variations on the motor shaft.

To achieve this, the setpoint value (desired speed) is continuously compared with actual speed. The difference obtained is applied to the motor through the power stage.

The setpoint value is input into the board using analogue voltage or a potentiometer.

Several control modes:

  • Tachymetric dynamo control
  • Digital encoder control
  • Compensation in RxI mode
  • Torque control

Each of these control systems has its advantages (+) and disadvantages (-).

The choice will be based on the type of application.

Tachymetric dynamo control

The tachymetric dynamo, which supplies a voltage proportional to speed, is directly mounted on the motor shaft. This enables limiting resonance frequencies at higher values.

 

 


  • (+) Classic solution with very precise control, especially at low speeds.
  • (-) Tachymetric dynamo size.
  • (-) Service life limited by the dynamo. Ideal for preserving good time constants.

Digital encoder control

A digital encoder mounted on the motor shaft generates a certain number of pulses.

Generally the encoder supplies two 90-degree staggered square signals, identifying the direction of rotation. The ratio of the number of pulses per unit of time becomes a voltage proportional to the speed.



 

 

  • (+) The digital encoder can also be used to control positioning or angular displacement.
  • (+) The encoder has no mechanical wear.
  • (-) Encoder size.
  • (-) There is less stability at low speed compared to control with the dynamo.

Ideal for cases in which, due to reasons of size and service life, the dynamo is not suitable.

 

Compensation in RxI mode

The motor is supplied at a voltage proportional to the selected speed reference. When the motor load increases, the current also increases and the speed tends to decrease. The compensation system detects this current variation and acts proportionally on the supply voltage.

It is important to adjust the system in accordance with the motor’s internal resistance. The value of this resistance may vary depending on temperature and applied load.



 

  • (+) Attractive price and reduced volume.
  • (+) No additional accessories (dynamo or encoder).
  • (-) Speed stability +/- 10%.

Ideal for simple applications without high time constant demands.

 

Torque Control


The motor receives a current proportional to the setpoint value. Consequently, the supplied torque is proportional to this value. The current controller is often used with a hierarchically superior position control unit.

 

Types of electronics

 

Divided into two types according to the working mode of the power stage:

1- Linear control

The operating voltage is divided between the motor and the power stage. The controller proportionally changes the motor voltage (Um) linearly. The voltage absorbed by the power stage (Ut) causes power dissipation.


 

  • (+) Simpler, more economical power stage
  • (-) Low performance

 

2- Pulse Width Modulation (PWM) control

The controller supplies the motor by pulses.

The average value of the voltage applied to the motor evolves according to cycle ratio (time on/time off). Power dissipation is very low.

 

  • (+) High performance
  • (-) More complex power stage

 

ELECTRONICS FOR BRUSHLESS MOTOR

The main mission of brushless motor boards is to ensure the rotation of the motor. Indeed, thanks to the processing of the signals from the Hall effect sensors, the electronics generates phase switching creating a similar movement to that of a DC motor.

Motor speed control is the second function of the electronics. Speed control is performed by the Hall effect sensors themselves or with an external device, such as an encoder or resolver. This latter option greatly improves speed at low revolutions.

The range of electronics for brushless motors includes two categories:

         - For three-phase brushless motors.

         - For four-phase brushless motors.

Control modes by means of Hall effect sensors and encoder/resolver are respectively comparable to Rxl compensation and by digital encoder for DC motors.

 

ELECTRONICS FOR AC MOTORS

These boards allow varying the speed of three-phase asynchronous motors by varying the supply frequency. In order to maintain a constant torque, the supply voltage/frequency (U/F) ratio is held constant. The output voltage will be kept stable beyond 50 Hz, the torque decreases with increased speed. So as not to decrease performance, the motors must not operate at a frequency higher than 150 Hz.

In the event of connecting to a self-cooled motor, it is recommended not to work with continuous current at under 20 Hz frequency. Turning the fan to low speed could lead to the motor overheating and destroy the winding.

Chopper frequency inverters generate parasites. In order to protect sensitive installations, they fulfil current EMC standards.

 

ELECTRONICS FOR STEPPER MOTOR

Stepper motors are electronically commutated motors, hence a suitable power module is required. The assembly is combined with a smart module that generates the positioning.

Power module:

The mission of the power module is to amplify the setpoint so that it successively applies voltage to the different phases of the motor. The card is similar to a square wave current generator where frequency acts on speed and voltage on motor torque.

Stepper motor electronics also allow control in microstep mode. This mode artificially creates a division of the basic step of the motor (1.8° for a 200-step/rev. motor in a maximum of 64 microsteps). This operation allows high resolution positioning.

 

Smart module: Controller

The intelligence module allows controlling the proper functioning of the automatism from the programming carried out and the information supplied by the sensors. This function can come from a controller, a PC or a PLC. It is important to know that a program-generated clock signal depends on the cycle of the automaton and the timebase of the timers, usually limited to 4 kHz.

Thus, a stepper motor associated with a power board and another to an axis control board with programmable sequences allows a quality positioning, simply and economically.

CONTROL ACCESSORIES

Generators

 

 

In motor/generator combinations, we propose DC generators supplying very stable voltages, regardless of temperature variations. The continuous voltage supplied is proportional to speed. Thus it is ideal for controlling and regulating speed.

The dynamo rotor is mounted directly on the motor shaft, which gives it high resonance frequency. The friction torque is limited to that of the motor. The dynamo ensures speed control and detects the direction of rotation.

 

 

Encoder



To control the speed and position of a motor, several types of encoders exist, supplying up to 1,000 pulses/revolution defining the direction of rotation and zero crossing.

Incremental encoders are based on the interruption of a light beam. A transmitter (LED) sends light through the lines of an optical disk fixed to the motor shaft.

The receiver (phototransistor) transforms the light signals received into proportional electronic pulses that are comprised of miniaturized electronics.

This signal, in which the pulses can be counted, allows the precise positioning of the motor. Thanks to two channels, A and B, two offset signals with which we can detect the direction of rotation are generated. One pulse per revolution (channel I) serves as a reference for the start of counting.

 

GEAR MOTORS

Gear motors associated with motors allow reducing speed while increasing the available torque proportional to the reduction ratio.

Spur pinions

Technology:

  • Series of cascading pinions guided by shafts mounted between boards or in box

Advantages:

  • High performance
  • Wide range of reduction
  • Compact: not very thick
  • Economic to manufacture
  • Output shaft offset and parallel to the motor shaft

Planetary

Technology:

  • Toothed crown on the inner periphery of the body of the gear motor
  • Satellite pinions guided on a disc that moves the output shaft or the following stage

Advantages:

  • High performance
  • Great ability to supply drive torque
  • Compact: small diameter
  • Allows high input speed

Worm gearbox

Technology:

  • Worm mounted on the motor shaft engaging with the gearbox input
  • Toothed crown at gear motor output

 

Advantages:

  • High irreversibility torque
  • Output shaft at 90°
  • Silent operation
  • Allows high input speed
  • Low torsional backlash
  • Possibility of hollow shaft