Analysis of New Energy Vehicle Relays and Contactors
Relay is a control component, which is a circuit switch with protective properties and is a core component of new energy vehicles.
Primary function
A switch that controls the on/off of a high-voltage circuit remotely using low voltage (using safe low voltages of 12V~72V to control unsafe high voltages of 300V~1000V);
Main function
This is commonly used in control circuits for automation. It essentially acts as an "automatic switch" that controls a large current with a small current, and it works together with other components in the circuit to form safety protection mechanisms and switching circuits, among other functions.
Key Features
Characterized by fast action, small size, high arc extinguishing safety, high reliability of action, and long life.
What is the difference between a relay and a contactor?
Initially, devices used for alternating current were called contactors, while those for direct current were referred to as relays. This distinction arose because contactors in AC systems tended to be larger, whereas DC systems utilized smaller versions of these devices, with some being universally called contactors.
Functionally, there is no difference between relays and contactors; both serve as control switches. Early on, contactors were primarily used in AC circuits. As DC circuit design focused on integration and miniaturization, a compact version of the contactor was developed for low-voltage DC applications and was distinguished by being called a relay.
However, as society advanced and the need for higher DC voltages and currents increased, relays evolved to include high-voltage models, and contactors underwent miniaturization. This development made it challenging to differentiate between relays and contactors, as neither the industry nor countries have established a standard distinction. Furthermore, the relay category has expanded to include various specialized versions such as time relays (which automatically connect or disconnect within a set time frame) and thermal relays (which do so based on detecting specific temperatures).
What's the difference between a relay and contactor as a power switch, compared to an ordinary switch?
High-voltage relays are primarily used as remote control switches in high voltage and high current applications.
In high voltage and high current environments, any circuit switching operation can generate arcs or sparks. The higher the voltage, the longer the arc produced; the larger the current, the greater the heat generated. An extended arc could potentially strike an operator or controller circuit or cause high temperatures to damage the control circuit board and render it ineffective, etc.;
For our daily household use with a voltage of 220V and a current of only about 10A, ordinary switches are sufficient;
However, in high-power, high-current industrial applications, specially designed switches are used. These systems are overly complex and massive, consuming a huge amount of energy, making them suitable only for specific projects;
As a result, remote control switch relays that meet the requirements of being compact, capable of handling high currents, low consumption, and safe arc extinguishing have been developed and are widely used in the new energy industry.
Why does a relay have positive and negative poles?
Not all relay contacts have positive and negative poles; this is only applicable to magnetic blowout arc extinguishing relays. The magnetic field has a certain directionality. Introducing current from the positive pole aligns the magnet's magnetic field with the arc's magnetic field, causing the arc to elongate and thin away from the contact point, thereby extinguishing the arc.
Conversely, introducing current from the negative pole results in the current's magnetic field repelling the core's magnetic field, pushing the arc closer to the contact point, forming a stable arc that is difficult to break.
For small current relays, where the arc power is low and easy to interrupt, a core is unnecessary, eliminating the distinction between positive and negative poles. This allows for a smaller volume, while other arc extinguishing mechanisms can also achieve polarity-neutral designs, albeit at the cost of larger volume or excessive energy consumption. Relays aim for lightweight and low consumption designs.
Difference between DC relay and AC relay?
For low-voltage relays, they are distinguished by the control current used, with those controlled by DC current being called DC relays and those controlled by AC current being called AC relays. The contacts can handle both DC and AC currents.
As for high-voltage relays, in addition to distinguishing them by control current, they are also differentiated by their contacts. When the contacts are for DC, there is a polarity distinction, and the arc produced is stable and unidirectional, allowing the use of magnetic blowout technology for rapid arc extinction. Relays whose contacts utilize magnetic blowout for arc extinction are known as DC relays. When the contacts are for AC, which lacks polarity, the arc produced is unstable and self-extinguishes without a consistent direction, and employing anti-arc leakage technology classifies them as AC relays.
What is the relationship between the main contact and the auxiliary contact?
Auxiliary contacts are used to detect the current state of the main contacts, check whether the main contacts are disconnected as per control instructions, and determine if the main contacts have failed.
What can relays and contactors do?
1. Relays in circuits can remotely connect and disconnect circuits, achieving remote switch functionality.
2. By switching on and off, they alternate current paths, enabling multi-path interchange capabilities.
3. This multi-path interchange allows multiple devices to share a line, thus facilitating device miniaturization.
4. They form part of automated control circuits with other components.
5. They contribute to real-time monitoring and safety mechanisms with other components.
6. In conjunction with systems, they provide protection against electric shock, fire, and equipment damage by automatically cutting off power.
7. They enable automation in industries.
8. Relays are core components in control circuits and also essential elements in new energy vehicles.
Application and Scope of High-Voltage DC Relays
1. The main focus is on the new energy industry, including cars, solar energy, wind energy, charging piles, storage systems, industrial automation, etc., to achieve power protection, automation, motion, remote control, measurement and communication, etc.;
2. In new energy vehicles, it involves switching and protecting the battery charging and discharging circuits, combining them into safety mechanisms against equipment failure or short circuits, fires, etc. It automatically detects and isolates faulty circuits to prevent further damage to equipment, save maintenance costs, protect against electric leakage, and effectively extend battery life. It controls the on/off of air conditioning, steering, brakes, air pumps, motors, etc., which are core components of new energy vehicles.
3. In charging piles, it cooperates with the system for automatic billing and power transmission and disconnection of the charging pile. It automatically detects and protects against overcharging, electric shock, electric leakage, and other improper operations.
4. In solar power generation, it is applied in real-time detection systems, assisting solar panel detection systems to isolate aging, damaged, short-circuited panels to minimize efficiency impacts. The system remotely controls panel maintenance to prevent electric shocks and leaks, save maintenance costs, and prevent damage expansion, thereby improving the lifespan of the solar panels.
5. In storage systems, it achieves circuit switching and builds an electric leakage detection system to prevent surge impacts on battery lifespan and protect against overcharging and over-discharging.
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