I'm building a switching circuit for a switched reluctance motor.

I have an open collector for the interface device, an optocoupler for the isolation device and an IGBT for the switching device.

How do I choose a specific open collector, optocoupler and IGBT? What am I supposed to be looking at in datasheets that will show that me what is suitable and what isn't?

 

Post a schematic of what you want to do.
What voltage and current does the motor require?

 

What is an Open Collector ?
Never new there is a component called open collector.

 

There's the circuit below. The parts I have chosen are parts that have been suggested to me, but I'm writing a report and I don't know how to justify why they are suitable. What should I be looking for in the datasheets?



Moderators note : Shown image full size

 

Hello,

The term "Open Collector" only tells you someting about the output of a device.
This device can be a transistor, comparator or gate.

Bertus

 

Hello,

The term "Open Collector" only tells you someting about the output of a device.
This device can be a transistor, comparator or gate.

Bertus

It's a transistor.

 

Hello,

Looking at the posted picture it is an 7406 logic gate with open collector.

Bertus

 

Hello,

Looking at the posted picture it is an 7406 logic gate with open collector.

Bertus

Yea, sorry, my mistake.

 

Main things to consider:
Voltage and current required by the motor.
Switching speed required.

 

The open collector logic gate should be able to drive the opto LED.
To find the desired info you need to look at the opto datasheet.
In that you will find the LED's forward voltage and it's current.
Those figures will tell you what is the value of the resistor to use for the LED current limiting.

The IGBT is always rated double the motor supply voltage and the motor current (for a safety margin ) And of course how fast you need to switch the motor like PWM.
Once you know the motor V, I and PWM (if you are using ) you need to look into the IGBT data to see if it can withstand the V and I and operate at the desired switching frequency.

 

Main things to consider:
Voltage and current required by the motor.
Switching speed required.

There's 12V going to to motor and it requires 3A per phase.

The requirements of the task aren't too specific. The motor just needs to operate, that's it.

 

There's 12V going to to motor and it requires 3A per phase.

What do you mean by " per phase"
Your diagram does not show more phases but a just a DC motor.
A stepper uses more than one phase.
A 3 phase motor uses more than 1 phase.

The requirements of the task aren't too specific. The motor just needs to operate, that's it.

Find an IGBT that can operate at around 50 to 60 V minimum and handle atleast 6 A

 

What do you mean by " per phase"
Your diagram does not show more phases but a just a DC motor.
A stepper uses more than one phase.
A 3 phase motor uses more than 1 phase.

That circuit I have shown is just 1 phase, I have to build that circuit x3.

Find an IGBT that can operate at around 50 to 60 V minimum and handle atleast 6 A

Why they values?

 

Find an IGBT that can operate at around 50 to 60 V minimum and handle atleast 6 A

Sorry for asking so many questions, I just don't have a clue how to look at data sheets.

What specifically am I supposed to be looking at on the IGBT data sheet?

 

Where did you learn electronics ?
Are you trying to make a circuit when you have no idea on choosing components and you do not understand datasheets?

How do you expect to troubleshoot when you got a problem ?

Are you trying to make a 3 phase motor drive or a stepper drive ????

 

It's a 6/4 pole switched reluctance motor.

I've just never had to use data sheets before to choose components. I know how the components operate, just not too good at looking through data sheets.



Looking at these values, this would definitely be suitable for the application, yes?

 

The TO-220 one will suffice
I will chose a the metal tab one for better cooling

What is your switching frequency ?

 

The TO-220 one will suffice
I will chose a the metal tab one for better cooling

What is your switching frequency ?

It doesn't have to switch at any specific frequency, the task just requires the motor to operate, that's it.