# Switching circuit for switched reluctance motor

• Engineering
• nothing909
In summary, the conversation is about designing a switching circuit for a switched reluctance motor using specific components. The circuit layout looks reasonable, but there is a question about the chosen resistance for the optocoupler's LED and whether it can be easily sourced. The datasheet is referenced for relevant data values and the question of required external components is brought up. The person designing the circuit calculated the resistance value, but it is suggested to use the "typical" values and round up to the nearest standard value for better performance.
nothing909

## Homework Statement

I have to design a switching circuit for a switched reluctance motor. Does this look like it will work. Any changes to me made?

The components are:

Open collector - 74LS06N
IGBT - stgp6nc60hd
Optocoupler - TLP 251

#### Attachments

• qwerty.jpg
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The general circuit layout looks reasonable.

How did you select the 350 Ω resistance for the TLP's LED? Is 350 Ω a standard resistor value that you can source, or will you have to build it up from multiple parts? Could you have chosen an easily available single standard resistance and still satisfy the TLP's operating requirements? What calculations might you do to check? What are the relevant data values from the datasheet?

Check the TLP datasheet schematic on page 1. Are you missing any required external components?

When you say am I missing any required external components, are you talking about the capacitor that needs to be connected between pins 8 and 5?

nothing909 said:
When you say am I missing any required external components, are you talking about the capacitor that needs to be connected between pins 8 and 5?
Yes.

other than that, everything else looks fine?

i calculated the 350 ohm resistor by doing 5 volts - 1.8 (Vf) = 3.2 and then I did 3.2/10mA = 320 ohm. is this correct?

nothing909 said:
other than that, everything else looks fine?
Yes, I think it should okay.
i calculated the 350 ohm resistor by doing 5 volts - 1.8 (Vf) = 3.2 and then I did 3.2/10mA = 320 ohm. is this correct?

It would probably be okay and not cause any issues, but I'd probably use the "typical" values for VF and IF to find a resistance value, then choose the nearest standard value resistor. Best to "round upwards" if the calculated value lies near the middle of two standard values.

## 1. What is a switched reluctance motor?

A switched reluctance motor is a type of electric motor that operates by the principle of reluctance torque. This means that the rotor is pulled towards the stator when aligned with the magnetic field, creating rotational motion. These motors are typically used in industrial and automotive applications due to their high efficiency and low cost.

## 2. How does a switching circuit work for a switched reluctance motor?

A switching circuit is responsible for controlling the flow of current to the stator windings of a switched reluctance motor. It works by turning on and off the different phases of the stator windings in a specific sequence, which creates the rotating magnetic field that drives the motor's motion.

## 3. What are the advantages of using a switched reluctance motor?

Switched reluctance motors have several advantages over other types of electric motors. They have a simple and rugged design, making them easier to manufacture and maintain. They also have a high torque-to-weight ratio, making them suitable for applications where high power density is required. Additionally, these motors have a wide speed range and can operate at high speeds without overheating.

## 4. Can a switched reluctance motor be used with variable speed drives?

Yes, a switched reluctance motor can be used with variable speed drives. In fact, this is one of the major benefits of these motors. The switching circuit can be controlled to adjust the speed and torque of the motor, making them ideal for applications that require variable speed operation.

## 5. What are some common applications of switched reluctance motors?

Switched reluctance motors are used in a variety of industrial and automotive applications. They are commonly used in electric and hybrid vehicles, as well as in pumps, fans, and other industrial machinery. They are also used in household appliances such as washing machines and air conditioners.

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