Thanks in advance. Suggestion To thank Quote Answer. Rate 2. Using a linear device such as a transistor in its linear mode is impractical for a VFD drive, since the power dissipated in the drive devices would be about as much as the power delivered to the load, The inverter circuit is probably the most important section of the VFD, changing DC energy into three channels of AC energy that can be used by an AC motor.
The usual method used to achieve variable motor voltage is pulse-width modulation PWM. With PWM voltage control, the inverter switches are used to construct a quasi-sinusoidal output waveform by a series of narrow voltage pulses with pseudosinusoidal varying pulse durations, Note: this is the part of the VFD where thyristorsor IGBTs circuitsare required. As new types of semiconductor switches have been introduced, these have promptly been applied to inverter circuits at all voltage and current ratings for which suitable devices are available.
Introduced in the s, the insulated-gate bipolar transistor IGBT became the device used in most VFD inverter circuits in the first decade of the 21st century. Hope this helps, Daniel Chartier. Hello dchartier, Great job,really thanks for your detail reply. It helped me a lot to understand the basic concepts. Variable Frequency Drives. Power Inverters. Voltage Converters. Soft Starters.
I would certainly say that thyristors are indeed extremely robust. So if you want very high peak to average current rating it may be this deliberate thing that is working against you. Thyristors are 4-layer devices with two sources of carriers in difference with IGBTs.
Click Here to See how you get new Article. You can see in the above diagram, the symbol of the SCR almost the same as the Diode symbol with an extra gate terminal. IGBT is a voltage control device, which means when a voltage applied to its gate terminal it will start conducting current, it does not consume any current in its gate terminal. On the other hand, SCR is a current-controlled device, which means it consumes some current through its gate terminal to operate.
The gate terminal of the IGBT is isolated, so it gives a very high safety when operating at high voltage, on the other hand, in the SCR the gate terminal is not insulated. Your email address will not be published. Coming from Engineering cum Human Resource Development background, has over 10 years experience in content developmet and management. Leave a Reply Cancel reply Your email address will not be published. Both devices are used in high power applications.
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