R&D and TECHNICAL SUPPORT MANAGER
Power electronics is a field of expertise that produces control systems that enable the management of high currents and voltages. There are many different application areas in this field, such as motor control, uninterruptible power supply, welding machine, energy transmission. Each application has its own specific issues and difficulties. Different materials have been developed to overcome these issues. In this article, we will focus more on motor control. One of the most commonly used materials in power electronics is switching elements. Switching elements are mainly grouped as BJT (Bipolar Junction Transistor), FET (Field-Effect Transistor), IGBT (Insulated Gate Bipolar Transistor) and Tyristor. There are many different types of technologies available in these main groups. These materials should be selected according to the targeted application. BJTs have an emitter, a base, and collector pins. The current that will pass through the emitter-collector depends on the current passing through the gate emitter. FETs, on the other hand, have a drain, a gate, and source pins. The current that will pass through the drain-source depends on the voltage between the gate-source pins. FETs can operate at higher frequencies, while BJTs can operate at lower frequencies. The current capacity of BJTs is higher than that of FETs.
IGBTs are the materials consisting of a combination of the good properties of BJT and FETs. They consist of IGBT Gate, Emitter and Collector pins. While the gate pin is triggered by voltage as in FETs, the current capacity is as high as in BJTs. The operating frequency is higher than BJTs and lower than FETs. MOSFET (Metal Oxide Field Effect Transistor) is the most commonly used type of FET. In addition, SICFETS (Silicon Carbide FET), which have been developed in recent years, offer high current, voltage and frequency. Generally, IGBT is used for high current and voltage, and medium frequency (20KHz), and SiCFET is used for high current and voltage and high frequency. The use of MOSFETS for medium and low voltage is also common. There may be value ranges where these products intersect, and the correct product selection should be made based on the characteristics of the application in hand, as well as the cost targets. Tyristor products have Gate, Anode and Cathode pins. Unlike other products, it remains in continuous conduction when the trigger is applied to the Gate pin, but it is reset when the voltage between the Anode and Cathode pins drops to 0 volts. This process is called sealing (latching). The product in which two Tyristors are connected inversely parallel to each other is “Triac”. Triac can work on both poles. Triac is more preferred for AC voltage and it needs to be able to be triggered at both poles since the sine signals are constantly changing poles. Dimmer applications are the most commonly used applications of Triac. Ozdisan Elektronik provides these products to its users with IXYS, FUJI and PANJIT brands.
“Although they are cost-effective, the disadvantage of induction motors is that speed control is difficult and their efficiency is lower than that of magnetic motors.”
Electric motors can be divided into two main groups as “brushed” and “brushless” as the driving method. There are many subgroups within these main groups as well. A rotating magnetic field is needed for the motors to move. Brushed DC motors have windings in the moving part called the “Rotor”, and permanent magnets in the outer part called the “Stator”. By means of conductive parts called “coal”, electricity is supplied to the windings and a magnetic field is generated. With this magnetic field, a moving magnetic field is created, as the winding that the coal energizes changes when the engine moves. Brushed motors are the motors with the simplest structure and low cost. The disadvantage is the heating problem, the losses due to friction are excessive and the service life is short. Brushless motors, on the other hand, can be in two different structures. In induction type motors, the windings are located in the Stator part and the copper rods are located in the rotor part. These motors usually create a rotating magnetic field at the network frequency using the 3-phase city network and motion is ensured by creating an opposite magnetic field as a result of the short-circuit current generated in the copper rods in the rotor part. In these motors, the rotation speed of the Rotor may not be synchronous with the magnetic field rotating in the Stator. Even if the rotor stops, the magnetic field in the Stator will continue to rotate. Therefore, these motors are also referred to as “asynchronous motors”. Although they are cost-effective, the disadvantage of induction motors is that speed control is difficult and their efficiency is lower than that of magnetic motors. Another type of brushless motors is “permanent magnet” motors. These are a newer technology than other motors, and their efficiency and service life are quite high as they have no friction parts. Today, their use has increased quite a lot. When we say BLDC (Brushless DC Motor) motor, usually these motors come to mind. BLDC motors with magnets can be driven by means of an electronic drive card. In BLDC motors, which are of Inner Rotor type, the windings are located on the stator and the magnets are located on the rotor. In outer BLDC motors, windings are located on the rotor, magnets are located on the stator. The moving part in these motors is the Stator. The motors used in Electric scooters can be shown as an example of this type. In BLDC motors, the position of the moving part where the magnets are located is detected by hall effect sensors and the magnetic field generated in the winding is synchronized. The rotating magnetic field in induction motors is provided by using the sinusoidal structure of the city grid. In BLDC motors, on the other hand, this rotating magnetic field is obtained from a DC voltage source with the help of an H Bridge circuit. H Bridge consists of 6 MOSFETs or IGBTs. BLDC motors have 3 phase windings and these windings need to be energized with a 120° angle difference. As with the sine signal, the electricity supplied to the windings must change one pole by 180 degrees. Angle differences between signals and the process of direction change are ensured by the 6-channel PWM output of a processor. Since the PWM outputs of the processor cannot be connected directly to IGBTs, an IGBT or MOSFET driver integration is needed. Additional circuits are needed to measure the motor current, protect the IGBTs in short circuit situations, and protect the IGBTs against excessive heat. The IPM modules developed by FUJI Elektronik have collected all these circuits and 6 IGBTs in a single package. In this way, by significantly reducing the number of external materials, it provides a cost and size advantage, and there are no Driver IGBT compliance issues. IPM modules make it easier to cool IGBTs with their cooler-mountable structure. The temperature of the IPM can be monitored via the temperature sensor output. With the FAULT output, error situations can be detected. Through the current detection input, the motor current can be limited and the motor is protected against short circuits. Ozdisan Elektronik It supports its customers with FUJIbrand.
“The IPM modules developed by FUJI Elektronik have collected all these circuits and 6 IGBTs in a single package. In this way, by significantly reducing the number of external materials, it provides a cost and size advantage, and there are no Driver IGBT compliance issues.”
