Amr Wael
Member level 5
Hello ,
I am testing a PCB for a three phase inverter it's mainly based on the circuit in the following photo
I am using Isolated DC to DC converter to isolate the VDD from the VCC.
My DC-Link voltage is 24V in a dual configuration +/- 12V
I am using an STM32 MCU to generate the PWM signal using famous SPWM algorithm.
The inverter output isn't actually bad however , there is a fluctuation in the DC Power supply voltage and the inverter is drawing current in milliamps without connecting any load.
The fluctation reaches 13V and sometimes even 14V then returns to 12V and sometimes it fluctuates below 12V. These supply fluctuations do not happen normally they occur only while the DC Link is connected to the inverter.
Ofcourse this leads to an output ripple voltage. Also, the value of the current drawn increased when tried increasing the dc link voltage because my inverter is supposed to work up to 400V , i Was just starting at low voltage. The dc supply indicated suddenly a short cirucit and one of the phases is actually not working as an IC is damaged.
Another point is that I hear low volume sound while the switching control signals are connected to the board. I tried monitoring the switching signals on the oscilloscope and they look fine. There is no overlapping between the signals with around 1 to 2 micro seconds between the switching of the complementary control signals for each bridge.
I tried adding a DC Link capacitors of values between 470 uF and 2000 uF between the DC Link +/- and the COM Respectively and the presence of these capacitor improved the supply fluctation. It now fluctuates between like 11.5 and 12.5V but it didn't affect the value of the drawn current at no load.
Any ideas on how to solve this problem and the reasons behind it ?
Thank you very much in advance !
I am testing a PCB for a three phase inverter it's mainly based on the circuit in the following photo
I am using Isolated DC to DC converter to isolate the VDD from the VCC.
My DC-Link voltage is 24V in a dual configuration +/- 12V
I am using an STM32 MCU to generate the PWM signal using famous SPWM algorithm.
The inverter output isn't actually bad however , there is a fluctuation in the DC Power supply voltage and the inverter is drawing current in milliamps without connecting any load.
The fluctation reaches 13V and sometimes even 14V then returns to 12V and sometimes it fluctuates below 12V. These supply fluctuations do not happen normally they occur only while the DC Link is connected to the inverter.
Ofcourse this leads to an output ripple voltage. Also, the value of the current drawn increased when tried increasing the dc link voltage because my inverter is supposed to work up to 400V , i Was just starting at low voltage. The dc supply indicated suddenly a short cirucit and one of the phases is actually not working as an IC is damaged.
Another point is that I hear low volume sound while the switching control signals are connected to the board. I tried monitoring the switching signals on the oscilloscope and they look fine. There is no overlapping between the signals with around 1 to 2 micro seconds between the switching of the complementary control signals for each bridge.
I tried adding a DC Link capacitors of values between 470 uF and 2000 uF between the DC Link +/- and the COM Respectively and the presence of these capacitor improved the supply fluctation. It now fluctuates between like 11.5 and 12.5V but it didn't affect the value of the drawn current at no load.
Any ideas on how to solve this problem and the reasons behind it ?
Thank you very much in advance !