Peer-to-peer, engineer-to-engineer questions and answers from the EDABoard.com engineering community around power electronics. Click the “Read more” link and follow the entire conversation and maybe add your two cents by logging in to EDAboard.com

VFD to control 3-phase AC induction motor – I want to control the speed of a woodcutter that is equipped with an asynchronous three-phase motor 400V 6000 RPM 6KW. From the searches, I came to the conclusion that a VFD would successfully solve my problem, so I decided to build one. Arduino DDS Sinewave Generator seems to me the simplest solution for adjusting the frequency. I tested this circuit and obtained a three-phase sinusoidal signal. Read more

This is the control board…

This is the gate driver…

Full bridge converter power factor correction – I have a 3 phase 400Vac supply rectified to 540VDC. A full bridge phase shift converter converts the 540VDC @10A to 10Vdc @500A. I am trying to figure out a power factor correction frontend for this converter (using UCC29910 from TI). The main question is: Buck or Boost? Read more

Temperature measurement on power MOSFETs – I am measuring case temperature by placing the thermocouples on MOSFETs in the bridge configuration of the motor control board. During the motor rotation or power consumption the six power MOSFETs are getting warm in my experiment. The question is how long we have to let it in running condition? Read more

Fully digital PWM amplifier – I need to drive 48Vrms into a few ohm speakers with a very short duty cycle (less than 10%) therefore with low average power. In this application, I am transmitting pre-recorded wav files. Frequency more or less is audio band. Read more

Flyback converter AL value  – In a flyback converter, how I can find equations or relation between the air gap and core loss? When I increase the air gap of exp N97, the reluctance will increase due to in core l(path in core) will increase. And AL value will less. The formula is L=N’2xAL, but I can not change L value because I calculated 320uH from power and efficiency. Read more

Opamp current regulator trying to limit overshoot in LED current – The two current regulators here try to keep the LED current from overshooting too much each time the LED voltage supply turns back ON. The one with the zener diode has the advantage that its opamp’s output voltage never gets railed high, and so it should offer less overshoot in the LED current when the LED supply voltage comes back on. However, its overshoot is just as bad as the other one, whose output does rail high. Why is this? Read more

30w flyback not giving output – I am making a 15V 2A (30W) CCM flyback converter with UC3843, and the feedback loop is with PC817 and TL431. I am not getting any output power at all. I am testing it with a 100W 8-ohm resistor. Read more

Stability analysis of DC-DC converter using PFM – We can apply PSS/Pstab Analysis of Cadence Spectre for DC-DC converter using PWM. However, we can not apply PSS/Pstab Analysis for DC-DC-Converter using PFM. If you will do stability analysis of DC-DC-Converter using PFM, what method do you use in simulation? Read more

Synchronous rectifier controller circuit for flyback – For flyback converter, I am planning to change secondary side. I want to change the output diode with MOSFET that has low Rds(on). But is there any analog circuit to make it without a special IC? Read more

Base-emitter resistor calculation – I want to use MMBTA2222A as a switch. Its hfe = 40 (min.), Vcc = 5V, Base input voltage is 14V. Series base resistor value I have calculated, but how to calculate the value of base to emitter resistor? Read more

BLDC controller stuck at load condition – We are designing a 3-phase inverter. Our controller worked fine at no load condition but when a load attached the controller gets stuck. Read more

Motors back emf…. with 120-degree phase-shift…