FAQ
Please use our new Search function to reach the result more quickly.
Stepper motors
(31 Entries )
Stepper motors have become firmly established in the field of positioning and accurate speed control. The characteristic features of the stepper motors can be seen in direct correlation of the electrical signals and the rotary motion of the stepper motor.
How do I find the relevant stepper motor?
To find the appropriate stepper motor for your application, primarily two important parameters are required that are provided to the motor. These are the torque that the motor should realize and the speed at which this torque should be reached.
On the basis of the motor curves that are stored on the website for every motor, you can then select the suitable motor. Our motor assistant helps you find the right motor.
Why are motors available with 4/6 or 8 connection leads?
The number of leads on a motor states something about the operation in which or with which positioning control this motor can be operated - unipolar, bipolar parallel, bipolar serial or with one winding half. The possible modes of stepper motors with 8 leads are extremely diverse as they are suitable for all types of positioning control and, hence, can be deployed very flexibly for the most different applications. Due to their flexible wiring the 8-lead motors are frequently also available ex warehouse.
How is a stepper motor constructed?
The stepper motor is made up of a magnetic rotor and several spatially offset stator coils. In order to generate a magnetic field, a current flows through the coils.
What are the features of a stepper motor?
Stepper motors offer the following advantages:
- Step-accurate positioning without external linear encoder (open loop)
- Digital control pulses for speed and position
- The speed is proportional to the input frequency
What is the difference between the unipolar and bipolar circuit?
Unipolar controls are suitable for 5-wire, 6-wire and 8-wire motors and are used for simple and cost-effective applications.
Bipolar controls are suitable for 4-wire, 6-wire and 8-wire motors and are used for high-performance and dynamic applications.
1. One half of the winding: Here only half of the windings of the motor are used, therefore the holding torque that can be achieved is also less than in the other modes. This mode only offers advantages in the high speed range of the 6-lead motors which is clearly apparent from the respective motor diagrams.
What are the features of bipolar operation?
Bipolar operation provides the possibility of connecting the two winding halves of the A and B phases in series or parallel.
Does the stepper motor have less torque in half step operation than in full step operation?
Full step operation
The stepper motor has the highest torque in full step operation. However, in full step operation a stepper motor also has the most marked resonance points - that, in turn, have a negative impact on the torque.
How is the required torque calculated?
The torque characteristics of the stepper motor show the dynamic torque against the speed or step frequency. Among other things, the dynamic characteristics of the stepper motors also depend on factors such as the type of power drive and the level of the supply voltage.
Rise in temperature at increasing speeds
In addition to the ohmic losses, the resetting losses primarily rise with increasing speed. These are also called iron losses and increase quadratically with the frequency.
What is the maximum admissible temperature?
The standard Nanotec motors of the ST series have insulation class B = 130 °C. This temperature must not be exceeded in the windings and in the ball bearings. (In the SP series the temperature relates to insulation class E = 120°C and to plain bearings).
With its rotor inertia and magnetic retaining forces, each stepper motor constitutes a damped oscillating system with low inherent damping. Thus vibrations can be induced that superimpose the actual step movements and a decrease in torque, loss of step or even a change of direction of rotation can occur.
Tips for dealing with resonance
- Microstep operation
- Reducing the phase current
- Changing the step frequency
- Increasing the friction
- Affixing a damper
- Changing the ramp gradient
- Reducing the tendency to oscillate
Is additional rotation monitoring required when stepper motors are used?
If a stepper motor is correctly dimensioned, it provides an absolutely reliable drive element. If stepper motors are overloaded, however, the assignment to the setpoint position is permanently lost. This behavior is described as “step offset“ and is deemed to be a serious disadvantage of the stepper motor because the out-of-position cannot be detected due to the open control chain.
A closed loop is a stator space vector monitor and evaluates the angular position of the stator vector.
Can a stepper motor be opened?
No, because opening the stepper motor ...
What is the recommended motor cable length?
The motor cable should not be longer than 25 m and must have a minimum cross section according to the current load table.
General information on the shielding of motor cables
Suppression measures should be carried out as directly as possible on the source of interference in order to prevent uncontrolled propagation of the electromagnetic faults through galvanic, inductive and capacitive coupling (also coupling between cables that run in parallel). There is a series of measures that can be implemented to minimize the transient emissions.
How do I change the direction of rotation of the motor
The direction of rotation is changed by swapping over two motor cords, e.g. phase A to A' and A' to A. Generally, however, the direction of rotation is changed via the direction inputs of the Nanotec positioning controls with a high or low signal.
What are the application advantages of stepper motors?
Stepper motors are digitally-controlled and regulated drives that have achieved the highest level of acceptance and prevalence since the technology transition (from analog to digital technology and current software solutions) due to favorable prices with maximum service life and little control required.
Turning and acceleration of flywheel masses
Often inquiries are received where only a well mounted rotary disk (e.g. 5 kg, diameter 30 cm) must be rotated and only the measurements and the weight are known as well as the required dynamics.
What effect do voltage drops have?
Particularly at higher speeds (from approx. 300-500 rpm depending on the motor winding), a too low motor voltage has an adverse effect on the field weakening which leads to the torque decreasing in proportion to the drop in voltage. From this perspective, synchronized power supplies such as the NTS.. are advantageous because they keep the voltage constant up to the nominal current and quickly compensate voltage drops.
Why does the current increase with decreasing voltage?
For reasons of energy conservation legislation, the sum of the potential energy and kinetic energy in a closed mechanical system always remains the same and cannot be deduced from the laws of physics.
Can a motor be operated with a higher voltage than specified on the motor type plate?
This data refers only to constant voltage operation that is actually hardly ever deployed nowadays due to the economical and considerably more efficient constant current drives such as the IMT901 or SMC(I).
Which start/stop frequency is possible or advisable?
The max. possible start/stop frequency depends on the frictional load or friction torque but principally on the inert external masses and is specified as fs at no-load operation of the motor in the torque characteristics (e.g. ST.. motor). If a straight line is placed between fs and the max. torque, in this approach the possible start/stop speed can found very roughly at the intersection point of the torque and straight line.
Which run-up ramp is ideal and how quickly can I reach the maximum speed?
The maximum acceleration behavior of the motor is determined primarily from the torque reserve at the desired operating point and the external inertial masses as well as the rotor moment of inertia of the motor. Exponential acceleration comes closest to the shortest run-up ramp with an initially very high and then asymptotic incoming ramp at its maximum value.
Step angle and steps per revolution
The number of steps per revolution of a stepper motor is made up of the pole pair number and the phase or stator windings, i.e. z = p * m (the rotor of the 2-phase hybrid stepper motors consists of 50 soft magnetic teeth that form a north and south pole due to the magnets lying between them while the 2 phases are wound on the 4 windings A + A/ and B + B/ of the respective pole shoe displayed by 90°).
What standard versions of stepper motors are there?
There are three specific versions of stepper motors:
I. Reluctance motors
II. Permanent magnet motors
III. Hybrid motors
Why do stepper motors lose steps rather more at high and lower speeds?
The lack of the torque reserve in both cases then leads to even a short increase in load or small torque peaks causing the motor to lose steps.
Is the torque dependent on current and voltage?
The torque is directly proportional to the current (P = I²/R) or generated magnetic flux provided the magnetization is within the linear section of the magnetization characteristic curve, i.e. not yet in saturation.
Stepper motor positioning controls
(9 Entries )
Do Nanotec positioning controls have an input for the encoder signal?
These functions are supported as standard by the SMCI 32, SMCI 47 positioning controls as well as in the PD-I motors of the Plug&Drive series. If other controls are deployed, this is only possible if a superordinate PLC takes over the analysis of the 5 V TTL level of the encoder and readjusts the clock of the clock input accordingly.
What advantages result from reducing the current (spec. when the motor is at a standstill)?
Because the holding torque is higher than the torque, a holding torque of the same size can already be reached with a lower current.
How does the positioning work?
The positioning is used to turn the stepper motor to a required target position.
Why exactly is a charging capacitor/intermediate circuit capacitor required?
When braking or stopping a stepper motor acts like a generator and gives energy to the power supply so that the power supply voltage increases. Due to the maximum admissible voltage of the transistors used and elements in the power drive, the braking energy or the voltage increase can damage the components in the power drive.
What power supply is required?
As all newer 2-phase stepper motor positioning controls are clock controlled (DC chopper controller), the specified phase current no longer needs to be multiplied by two. Instead, the power output of the power supply units must be calculated with the mechanical power of the motor P = Md* n * ?/30 plus the efficiency of the motor, controller and power supply unit.
Is there any loss of position when the motor control is switched off?
If the rotor is also to retain its position at a standstill, the stepper motor must remain actuated/energized. Nanotec positioning controls have an enable input which is used to deactivate the drive and deenergize the motor.
Determining the motor power (rule of thumb)
The max. speed and torque are required for the stepper motor selection and, ideally, the flow characteristics that are however only rarely available.
Which microstep setting is the most suitable?
This depends greatly on the respective speed and primarily also on the requested speed range. If only a low/high speed is necessary, the rule of the highest possible/lowest possible microstep fits as the resonance and noise are largely reduced at low speeds
Are high microstep resolutions > 32/1 advisable?
The temptations to purchase a stepper motor drive that enables as high a microstep setting as possible in order to achieve a high resolution and hence also a high accuracy are often irresistible. The aim is certainly tempting to order a drive with a resolution of 1/128 (in a 1.8° stepper motor mathematically = 0.0140625°/step = 25600 steps/rev), for example, only to suffer a heavy setback in terms of accuracy when testing.
Linear actuators
(1 Entry )
What are the specific features of the Nanotec linear actuators?
The achievable resolution, precision feed control speeds and forces are calculated on the basis of the pitch of screw (p in mm), propelling torque flow characteristics (Md in Ncm) and efficiency as follows:
Old part numbers
(7 Entries )
Click on More for an overview!
Click on More for an overview!
Click on More for an overview!
Click on More for an overview!
Click on More for an overview!
Click on More for an overview!
Click on More for an overview!
