By: Luis Cordova
What are laminations?
Electrical DC motors comprise two main components the stator and the armature. The stator is the motionless component of the motor, while the armature is the revolving component. Once the core begins to rotate in the magnetic field, a voltage begins to be generated in the coils resulting in eddy current or power loss. Laminations help to reduce the development of eddy currents and prevent magnetic loss.
Modern laminations are composed of silica steel, cold-rolled, and grain-oriented steel. Generally, they are steel that is die punched or made by laser cutting. Their design has specific profiles and dimensions to accommodate assembly. They are typically between 29-26 gauge steel and can have a thin insulation coating. Insulation coatings reduce circulating currents and heat build-up.
How are stator cores built up?
A stator core is laminations stacked and layered offset to each other to form a ringed layer. Stator cores can be short or made of thousands of layers, depending on their final use. They are bound together using compressive load incorporating key bars, building bolts, through bolts, finger plates, and compression rings.
What does a laminated stator core do?
A stator core’s function is to hold the stator winding and transmit flux. A stator provides the magnetic field necessary to drive the rotation of an armature in motors. In generators, the stator converts the rotation of the magnetic field into an electric current. In fluid-powered machines, the stator guides fluid to or from rotating parts.
In motors, eddy currents decrease performance, decrease efficiency, and cause power losses. The function of the laminated stator core is to keep constant power and operate efficiently. Overall they’re designed to reduce eddy currents and increase the efficiency of motors.
Apart from eddy currents, hysteresis occurs in many stator cores. Hysteresis is the loss of or reversal of magnetization in stator cores. In other words, the production of heat from the stator core causes hysteresis, which impacts energy and power loss. Lamination plates prevent this event by narrowing the hysteresis loops, decreasing energy loss, and improving efficiency.
As previously mentioned, heat production can cause power loss and breakdown of motors. Laminated stator cores help to reduce the amount of heat produced. Heat reduction is achieved by providing a cool-down period for the stator core. However, over time the performance of the laminated stator core will slowly deteriorate, requiring repair or restacking. Laminated stator cores are one of the most significant technologies to many industries. To better understand if a laminated stator core achieves its potential, Soken has developed its Lamination Stator Tester (DAC-LST-3).
How does Soken Lamination Stator Tester work?
Primarily, the LST-3 tests the lamination stator core for motors. Soken’s LST-3 has turned conventional testing upside down by introducing a PWM inverter to magnetize the stator core and increase its accuracy. The quality of the lamination stator core is judged by comparing the value of magnetic flux density, magnetizing force, and iron loss to a standardized Japanese quality laminated stator core. Due to the new design, the LST-3 is compact, lightweight, and has a stabilized output voltage. Frequency testing is changeable n the range of 50-400 Hz. The LST-3 features include adjustable excitation of the power supply, decreased interference, and remote data measurement to a PC.
In Thailand, Hemmawit supplies LST-3s to companies that desire Japanese quality measurement of laminated stator cores to their customers. Hemmawit customers trust the quality of products that Soken can provide. Soken’s commitment to quality products allows for many of these testing units to last for five years or more under normal operation without any breakdowns. Hemmawit is proud to provide Soken products in Thailand for over 20 years. We hope our customers can elevate their products using Soken’s testing meters for their production.
Luis Cordova
Luis is a professional medical and technical writer with years of experience in the industry. Originally from Texas, he has resided in Thailand for many years. He has many years of experience in agriculture, research, and writing on various topics.