Power Mosfet Selection

Thread Starter

pilko

Joined Dec 8, 2008
213
Hi All,
I am in the process of sourcing a Power Mosfet for 20KHz PWM driving a 90V: 0.5HP permanent magnet shunt motor. I will be using a driver.
I have found a STP30NF20 (data sheet attached).
It looks good to me because of the following specs:

VDSS = 200V
ID = 30A
RDS(on) = 0.075 Ohms
Total Gate charge = 38nC

Can some one tell me if it is suitable for motor driving. The reason I ask is because of the following description in the data sheet.

Application​
■​
Switching applications

Description​
This Power MOSFET series realized with
STMicroelectronics unique STripFET process has
specifically been designed to minimize input
capacitance and gate charge. It is therefore
suitable as primary switch in advanced highefficiency​
isolated DC-DC converters

regards
pilko
 

Attachments

crutschow

Joined Mar 14, 2008
24,741
What is the maximum motor current?

It looks suitable for your application.

Make sure the driver can charge and discharge the total gate charge rapidly enough to give short rise and fall times for the gate voltage and minimize switching losses.
 

Thread Starter

pilko

Joined Dec 8, 2008
213
Thanks for the response crutschow.
The full load current in my app is 7 Amps; The inrush is 18A >>>7A in less than 1 Sec.

pilko
 

JDT

Joined Feb 12, 2009
657
You should use a MOSFET driver that can quickly deliver large currents to charge and discharge the gate capacitance.

Also important is having an "undervolt lockout" so that you never partially turn on the MOSFET - on power up or during loss of power for example.

A partially switched on MOSFET with only a small gate voltage will be instantly destroyed due to internal power dissipation or secondary breakdown. I know from experience!

The gate driver IC MC33152 (for example) has this built-in.
 

Thread Starter

pilko

Joined Dec 8, 2008
213
Thanks JDT.
I am now trying to calculate the required gate driver current from I = Q/dT,
but I am unsure what to use for dT. The data sheet quotes:

Turn-on delay time
Rise time
Turn-off delay time
Fall time

Help would be appreciated

pilko
 
Top