Technical Information

Hybrid Step Motors combine the best characteristics of variable reluctance and permanent magnet step motors. Because they exhibit high static and dynamic torque and run at very high step rates, Hybrid Step Motors are used in a wide variety of industrial applications.

Hybrid Step Motors are highly precise, digitally controlled motors that are able to provide years of reliable operation. The operation of the motor is controlled through electrical pulses. The direction of current flowing through the windings of the motor is switched with each pulse. The electrical pulse is converted into shaft rotation in steps of a fixed angle. Together with the driver, it constitutes an open loop system, which is cost effective and simple to construct.

Hybrid Step Motors, as a result of the way they are constructed, are inherently lower cost than servo motors. Step motor systems do not require tuning, allow for greater inertia mismatch and have a very high torque density. This torque is 100% available immediately upon startup which can be very advantageous when doing short quick moves or when coupled with high inertia loads. Because step motors are synchronous motors with a high pole count, they are able to run smoothly at extremely slow speeds with little torque ripple. These precise, highly reliable motors are applied in thousands of applications in industries such as medical, lab automation, electronic assembly, and packaging. Popular for decades, these systems will continue to be a popular choice among design engineer.

BIPOLAR VS UNIPOLAR STEP MOTORS

All motors in this catalog are Bipolar. Bipolar motors have a single winding per phase. The current in the winding needs to be reversed in order to reverse a magnetic pole. Therefore, the driving circuit is more complicated and typically utilizes an H-bridge arrangement. Because windings are better utilized, they are more powerful than a Unipolar motor of the same size. A Unipolar motor has twice the amount of copper wire in the same space, but only half is used at any point in time, hence it is 50% efficient.

BI-POLAR CHOPPER DRIVE

Bipolar chopper drives are by far the most widely used drivers for industrial applications. Although they are typically more expensive to design, they offer high performance and high efficiency. They also use a four transistor bridge with recirculating diodes and a sense resistor that maintains a feedback voltage proportional to the motor current. The motor performance curves in this catalog were developed using a Bi-polar chopper drive.

PULL-OUT TORQUE

Measured by accelerating the motor to the desired speed and then increasing the torque loading until the motor stalls or missed steps. This measurement is taken across a wide range of speeds and the results are used to generate the dynamic speed / torque curve. This curve is affected by drive voltage and drive current. All performance curves in this catalog are generated using this method.

MOTOR ACCURACY

Approximately ± 3 arc minutes (0.05 degree) This error does not accumulate from step to step. When a standard 1.8 degree step motor travels one step is will go 1.8 degree ± .05 degree. If the same motor travels one million steps, it will travel 1, 800,000 degrees ± .05 degree. The error does not accumulate.

PHASE INDUCTANCE (MH)

Step motors are rated with a varying degree of inductance. A high inductance motor will provide a greater amount of torque at low speeds and lower torque at higher speeds. PHASE RESISTANCE (OHMS) The motor‘s terminal resistance value specified at the the hot winding, which is the motor‘s maximum rated temperature.

HOLDING TORQUE

The maximum torque that can be externally applied to the stepper motor shaft without causing continous rotation when one or more phases of the motor are energized.

DETENT TORQUE

The torque required to rotate the motor‘s output shaft with no current applied to the windings. RADIAL LOAD A load exerted perpendicular to the motor shaft (should be minimized).

Note:

• •• 0.9 ° step angle is also available

• 2-phase motor basic angle is 1.8°

• 3-phase motor basic angle is 1.2°

• 5-phase motor basic angle is 0.72°

APPLICATION CONSIDERATIONS

In order to select the right motor, several factors should be considered:

• How much torque is required?

• What is the desired step angle? (resolution)

• What is the speed requirement at rated torque? (RPM)

• Detent or holding torque requirements

• Physical size restrictions?

• What type of driver (amplifier) are you using?

• Environmental considerations?

ENVIRONMENTAL CONSIDERATIONS

DINGS‘ linear motion systems are designed to operate in dry and non-corrosive environments. Operating the motor in dirty, corrosive, or extremely high temperature environments will significantly reduce product life and may void warranty. Using the Product Selection System along with the associated Nema motor frame size pages in the next sections, you will then be able to drill down to specific part numbers for your step motor choice.

NEMA MOTOR SIZE

Based on Standards Established by the National Electrical Manufacture‘ Association (NEMA). The size of motor is established by overall dimension of motor flange. For example, a NEMA 23 motor measures approximately 2.3 inches square at the mounting flange.

HYBRID STEP MOTOR

The Hybrid Step motor is the most widely used and combines the principles of the permanent magnet and the variable reluctance motors.

NUMBER OF MOTOR ELECTRICAL PHASES

2, 3 or 5 phase. 2-phase is the most common. The potential advantages offered by a 5-phase motor are higher resolution, lower acoustic noise, lower operational resonance, and lower detent torque. The 3-phase motor offers a middle course between the 2-phase and 5-phase step motor.

STEP ANGLE

Step angle of the motor is defined as the angle traversed by the one motor one full step. For example, a 1.8 ° step angle would have 200 full steps per revolution. 360 / 1.8 = 200

MOTOR LENGTH

Determined by the # of rotor cups or stacks. Added stacks and length = more torque, but at a tradeoff. Depends on the application; for example, a longer motor has higher slow speed torque but at the expense of quick response and higher speeds. Rotor inertia also increases with longer motors.

RATED CURRENT / PHASE

The higher the current / phase the more performance. The motor driver (amplifier) may also determine which current to choose.

NUMBER OF LEAD WIRES

Step motors typically come with 4, 6, or 8 wire leads. With bipolar driver, there are 4 connections to a motor. Wiring up a 4 lead motor is straightforward. When using motors with 8 leads, the coils can either be connected in series or parallel.

Lead Wire Configuration

A series connection provides a higher inductance and therefore greater performance as low speeds. A parallel connection will lower the inductance but increase the torque as faster speeds.

SHAFT CONFIGURATION

Single or Double If an encoder or brake need to be mounted, a double shaft (rear) will be required

ENCODER OPTION

If it necessary to confirm position attained back to the motion controller, an encoder will be required. The resolution (or line count) of the encoder will be dependent on the application. A 1,000 line encoder, with quadrature, provides a 4,000 count resolution. In addition, a single ended electrical connection or differential are available. A differential encoder option is recommended for longer encoder cables and/or high noise environments.

CUSTOM CONFIGURATION

DINGS‘ can provide a custom configuration to your specification. This can include special windings, connectors, wire leads, and mechanical modifications to both the front and rear shaft. Contact your local technical distributor for quotation.