What are the protective measures for power devices

Power devices are electronic components with relatively high output power. They are the general term for electronic components and equipment. They are power amplifiers.. Power amplification uses the current control function of a triode or the voltage control function of a field effect transistor to convert the power of a power source into a current that varies according to the input signal. It is mainly composed of electronic component industry, semiconductor discrete device industry, and integrated circuit industry.. Power electronic devices are widely used in power electronic devices such as power supplies, servo drives, frequency converters, and motor protectors.. Next, we will mainly introduce the protection measures for power devices..

What are the protective measures for electrical equipment?.

This is a traditional protection. Fuses are often connected in series with the power input of a circuit to control the total current of the entire circuit. Its working principle is to rely on the increased fault current after a circuit fault to flow through the fuse, causing it to heat and melt itself, thereby cutting off the power supply and achieving the purpose of protection.. The fuse method has the advantages of simple implementation, easy maintenance, low cost, and being able to completely cut off the power supply during protection. Therefore, it is widely used in all electronic circuits and equipment at present.

However, because the total current of a circuit flows through a fuse, changes in the operating current in a single power semiconductor device are not sufficient to cause its effective response. In addition, the melting speed of the fuse is slow, and it can only be blown when the power semiconductor device is damaged or the fault current doubles after a malignant short circuit fault occurs. Therefore, it can only prevent further expansion of the fault and has no impact on power semiconductor devices. For protection.

2. Method of detecting main circuit current.

The method is to connect the detection elements in series to the input terminal of the main circuit power supply. Sensing resistors, transformers, etc&# 41。 The voltage drop or current magnitude of the total current in the detection circuit is detected on the detection element to obtain a corresponding current or voltage signal, which is amplified and processed by the circuit, and compared with the action threshold of the protection circuit to determine whether to protect.

Due to the use of electronic technology, this protection method has improved sensitivity and response speed compared to the fuse method. However, this method still detects the total current of the circuit, and the operating current of the faulty power semiconductor device only accounts for a small portion of the total current. This change is not sufficient to cause an effective response of the protection circuit.

Therefore, this method always responds after the formation of fault currents, resulting in delayed detection results and protection actions, which simply cannot meet the protection requirements of power semiconductor devices.. Therefore, this protection method is the same as the fuse, and can only prevent further expansion of the fault after the power semiconductor device is damaged and a malignant overcurrent fault occurs.. The protection of power devices is still powerless.

This is a relatively common protection method for power semiconductor devices, which has a certain protective effect on power semiconductor devices.. The method is to insert a detection element in series into the working current path of the protected power semiconductor device. Resistance or current transformer, etc., The current or voltage signal of the working current of the protected device is detected on the detection element, and then the fault signal is obtained through circuit processing. Then, it is protected by using a fuse or cutting off the power supply.

The working principle and circuit structure of the method for detecting the working current of a power device are the same as the method for detecting the main circuit current. The difference is that the detection object is the working current of the protected device, so it is more sensitive and effective than the method for detecting the main circuit current. 2。 If the protection method of switching off the current path of electronic devices is adopted, it can play a certain protective role in the event of overcurrent faults in electronic tubes..

4. A method for detecting the voltage of power devices in parallel.

As the name implies, this method is to connect the protection circuit in parallel with the protected power device, obtain a signal by detecting the voltage at which the protected device is operating, and determine whether the circuit has failed based on the voltage situation. The protection method adopts the local protection method, which is to forcibly cut off the control signal of the protected power supply device itself and force it to stop working to achieve its protection 40。 Detect the voltage of the protected device and directly protect the protected device&# 41.

Due to the conduction resistance of the power semiconductor device itself, any overload and overcurrent will cause an increase in its saturation voltage drop or operating voltage drop. That is, regardless of the operating state of the semiconductor device, the device itself will have a corresponding operating voltage drop. Monitor and monitor the voltage drop during the conduction of power semiconductor devices, and determine the condition and degree of overcurrent and overload based on the magnitude of the voltage drop.

The working principle and connection method of this method are the same as the working state voltage detection method of parallel power devices, so it also has all the advantages of the working state voltage detection method of parallel power semiconductor devices. The difference is that this method quantitatively detects the operating voltage of the protected device, making it more accurate to measure the operating state and judge faults. 2。 This method can detect and realize the protection of power semiconductor devices against underexcitation, overcurrent overload, load short circuit fault, and the effect is very ideal.