Efficiency and Performance Comparison of Hybrid and Permanent Magnet Linear Stepping Motors

Customers will call us to ask why the 43000 hybrid linear stepping motor has a 7W input power but a better performance than the 46000 permanent magnet linear stepping motor with a 10W input power. The answer is the efficiency of the Micro stepper motor driver itself. The average efficiency of hybrid motor is about 65%, while that of permanent magnet motor is about 25%. There are two main reasons for the difference in efficiency. The first reason is that the hybrid motor uses silicon steel laminated stator assembly (see Figure 1). Compared with the low carbon steel stamping stator assembly of permanent magnet motor, the laminated stator of hybrid motor has less eddy current loss and the silicon steel material in laminated structure can be reduced. Less hysteresis loss; therefore, the overall iron loss of hybrid linear motor is smaller than that of permanent magnet motor, so the hybrid motor is more efficient. At the same time, the step angle of hybrid motor is 1.8 degree or 0.9 degree. Compared with the step angle of permanent magnet motor 15 degree or 7.5 degree, the resolution of each step is increased to 0.000060 inch [0.001524mm]. Compared with 0.00025 inch [0.00635mm], hybrid motor has better positioning performance. Figure 1: Silicon steel laminated stator assembly and low carbon steel stamping forming assembly. The second reason is the magnetic circuit of the motor. The structure of hybrid motor makes the air gap between stator and rotor about 1/2 of that of permanent magnet motor. The typical design air gap of hybrid motor is 0.003-0.004 inches (0.0762-0.01016 mm), compared with 0.007-0.008 inches (0.1778-0.2032 mm) of permanent magnet motor. Smaller air gap provides more efficient magnetic coupling, which leads to higher torque. See Figure 2. Size 17 (43000) hybrid motor and 46000 permanent magnet motor with single stack thickness, corresponding to 7W and 10W input power, the same screw, the same linear speed performance comparison curve, the hybrid motor is higher. Fig. 2 The air gap ratio of hybrid and permanent magnet motors has the following advantages compared with permanent magnet motors: 1. Linear stepping motors have special advantages in positioning applications, because the motor rotates one step for each pulse of the controller. The resolution of motion depends on the lead of the screw and theMicro stepper motor driver. The step angle of 1.8 degree or 0.9 degree of hybrid motor (15 degree or 7.5 degree of step angle of typical VS permanent magnet motor) improves the resolution to 0.000060 inch [0.001524mm]. Compared with 0.00025 inch [0.00635mm] of permanent magnet motor, hybrid motor has better positioning performance. 2. In many applications, the installation of motor plays a vital role in the performance of the whole system. The front cover of the hybrid motor has a positioning convex platform concentric with the motor bearing, so the motor can be better centered in the mechanism when installed. See Figure 3. Figure 3: The positioning bump is beneficial to the concentricity of installation. The hybrid motor can install the encoder more conveniently, so as to achieve the goal of closed-loop control. Because the metal rotor shaft used in hybrid motors can be machined to a more precise dimensional tolerance, better installation with coder disc, reduce jitter and use a higher resolution coder disc. 4. Improving the output performance without changing the size of the motor is the requirement of many applications. Hybrid motors with the same flange size can provide several different output powers by changing the overall motor thickness. Permanent magnet motor needs to readjust and design the whole set of die, which requires a relatively large investment in the cost of die. In summary, compared with permanent magnet motors, hybrid motors have higher efficiency due to their smaller iron loss, smaller stator and rotor air gap and higher output power density. These performance characteristics do affect the cost; permanent magnet motor is a feasible low-cost solution under the requirements of adaptive thrust, speed and resolution. If your application requires high repetition accuracy, high resolution, high speed stability, or customized high efficiency modules, hybrid motor is the ideal solution to meet your requirements.