Hello, thanks for your question! Looking at the A+, switching at a certain duty cycle δ, a current of value I passes through it for a time δTs (Ts being the switching period) in the first half cycle. In the second half cycle A- is switched with duty cycle δ, while A+ is then switched on for (1- δ)Ts. Therefore, during the hole control cycle a single switch conducts the current equivalent of half a control cycle. This means that the switch conducts only one third of the control cycle. Therefore the conduction losses are (Eq 10) Pcond =RDS(on) 1/32. Have a read here: www.nexperia.com/applications/interactive-app-notes/IAN50009_Power_MOSFET_applications_in_automotive_BLDC_and_PMSM_drives.html
Hello. 70/30 sounds good. It can be anywhere between 40/60 to 80/20. This is because of low switching frequencies (up to 30kHz but can be as low as 10kHz). This can be opposed to BLDC which can go up to high rotor speeds and thus high switching frequencies. In that case switching losses can dominate substantially. Same goes for DC/DC converters (buck) where the minimum is 100kHz switching causing 5 times more switching losses.
Very good
Nice one and I have one doubts. In the final equation, the conduction losses are mentioned as Rds x i2/ 3. How it is calculated
Hello, thanks for your question! Looking at the A+, switching at a certain duty cycle δ, a current of value I passes through it for a time δTs (Ts being the switching period) in the first half cycle. In the second half cycle A- is switched with duty cycle δ, while A+ is then switched on for (1- δ)Ts. Therefore, during the hole control cycle a single switch conducts the current equivalent of half a control cycle. This means that the switch conducts only one third of the control cycle. Therefore the conduction losses are (Eq 10) Pcond =RDS(on) 1/32. Have a read here: www.nexperia.com/applications/interactive-app-notes/IAN50009_Power_MOSFET_applications_in_automotive_BLDC_and_PMSM_drives.html
what is the percentage loss distribution in switching loss and Conduction loss in PMSM? Can we say 70% Conduction and 30% switching loss?
Hello. 70/30 sounds good. It can be anywhere between 40/60 to 80/20. This is because of low switching frequencies (up to 30kHz but can be as low as 10kHz). This can be opposed to BLDC which can go up to high rotor speeds and thus high switching frequencies. In that case switching losses can dominate substantially. Same goes for DC/DC converters (buck) where the minimum is 100kHz switching causing 5 times more switching losses.