Discharge circuit in electric vehicle

In summary, when designing an electric car, the motor controller contains capacitors that need to be discharged to prevent high inrush of current. A precharge resistor is attached to the contactor to achieve this. To discharge the capacitors, a resistor can be connected in parallel or diodes can be used. The value of the resistor must be carefully chosen to balance power efficiency and discharge time. A solid state device is recommended for controlling the motor speed in a car, as electro-mechanical relays are not suitable. The discharge resistor in industrial systems may have a longer discharge time compared to vehicles, where efficiency is prioritized. A circuit diagram is needed to determine the best solution for discharging the capacitors in the motor controller. One
  • #1
nikita
11
0
we are designing a electric car. in that motor controller has capacitors which get charged when supply is given.so across the contactor we are attaching a precharge resistor,which prevents the hiigh inrush of current in motor controller. now we are stuck on the ques that how to discharge the capacitors? what is a discharge circuit?
 
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  • #2
A circuit diagram of what you have so far would be helpful.

In general you can connect a resistor in parallel with the capacitors to discharge them. There will be engineering concerns with the value of the resistor. It will have to be high enough so that you are not wasting power by running a high current through it but also not so high that it takes too long to discharge the capacitor. It all depends on your application. Look up RC circuits to see more on that.

It's also pretty common to use diodes to discharge capacitors in voltage regulators and motor drivers. A circuit diagram would be needed to see exactly what your application does and where a diode might be appropriate.

When you say contactor are you talking about an electro-mechanical relay? That would not be a good choice for a variable speed motor application like you might have in a car. A solid state device would be much better. The reason is that you typically control the duty cycle of a DC motor to regulate its speed and torque. An eletro-mechanical relay doesn't switch quickly enough or reliably enough to do this properly. The contacts in a contactor also wear out over time from electrical arcs.
 
  • #3
The concept in vehicles is often to make a mechanism that connects a discharge resistor - before the access to the capacitors ( or batteries) is allowed.

Usually just discharged through a resistor. For example - you can use a screw in a cover plate to press a limit switch, as the screw is removed the switch closes completing the circuit through the discharge resistor.

Oh... in industrial systems the Resistors are sometimes left on permanently, and may have a 5 minute discharge time, and be labeled as such. IN the Vehicles they care more about efficiency and want a faster discharge - so a different solution is used.
 
  • #4
circuit diagram

this the circuit diagram.please refer and help me how to discharge the capacitors in controller
 

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  • #5
Can you add a NC contact to the key switch? ( i.e. the the key is off or removed, the contact is closed?)
 

Related to Discharge circuit in electric vehicle

1. What is a discharge circuit in an electric vehicle?

A discharge circuit in an electric vehicle is a system that controls and regulates the flow of electricity from the battery to power the vehicle's motor. It is responsible for converting the battery's direct current (DC) into alternating current (AC) to power the motor.

2. How does a discharge circuit work?

A discharge circuit works by using a series of components such as diodes, capacitors, and transistors to convert the battery's DC into AC. The AC is then sent to the motor at the appropriate voltage and frequency to power it. The circuit also includes safety features such as fuses and circuit breakers to protect the vehicle from electrical malfunctions.

3. What are the main components of a discharge circuit?

The main components of a discharge circuit include a battery, an inverter, a motor controller, and various safety features such as fuses and circuit breakers. The inverter is responsible for converting the DC from the battery into AC, while the motor controller regulates the flow of electricity to the motor.

4. Why is a discharge circuit important in an electric vehicle?

A discharge circuit is essential in an electric vehicle because it controls and regulates the flow of electricity from the battery to the motor. Without it, the motor would not receive the correct voltage and frequency needed to function, and the vehicle would not be able to run. The circuit also includes safety features to prevent electrical malfunctions that could be dangerous for the driver and passengers.

5. Can a discharge circuit be upgraded or modified?

Yes, a discharge circuit can be upgraded or modified to improve the performance of an electric vehicle. Upgrading the inverter or motor controller can increase the vehicle's speed and power, while modifying the safety features can enhance the vehicle's safety. However, it is essential to consult a professional and make sure the modifications are compatible with the vehicle's existing components.

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