DC and AC models of Chint small relays
There are significant differences between DC and AC models of Chint small relays in terms of design principles, structural characteristics, and application scenarios. The specific analysis is as follows:
I. Differences in Core Working Principles
1. **Coil Power Supply Type**
- **DC Relays**: They need to be connected to DC voltage (such as 6-220VDC), and the coil generates a magnetic field through direct current to drive the contact action. A typical model is NXJ/2ZH(D) 12VDC, whose coil has strict polarity requirements. Reversing the connection will cause the indicator light to fail or the coil to be damaged.
- **AC Relays**: They use AC voltage (such as 6-380VAC), and the coil drives the contacts through the alternating magnetic field of alternating current. For example, HH52P-AC220V has no polarity requirements and allows for more flexible wiring.
2. **Arc Extinguishing Mechanism**
- **DC Relays**: Since DC current has no natural zero-crossing point, the arc is difficult to extinguish. Chint, through its patented technology (such as CN109585224B), integrates a permanent magnet magnetic field into DC relays. It uses the Lorentz force to introduce the arc into the cooling chamber for arc extinguishing, making it suitable for high DC loads.
- **AC Relays**: The alternating current periodically crosses zero, so the arc is easy to self-extinguish. For example, the AC models of the NJX6 series adopt silver alloy contacts and an optimized structure, which have high arc-extinguishing efficiency and do not require complex arc-extinguishing devices.
II. Comparison of Structural Design
1. **Iron Core and Short-Circuit Ring**
- **DC Relays**: The iron core is mostly made of soft iron and has no short-circuit ring. For example, the iron core design of DC models in the JTX series pays more attention to magnetic field stability to ensure quick contact closure.
- **AC Relays**: The iron core is made of silicon steel sheets to reduce eddy current loss and has a built-in short-circuit ring (such as HH54P) to offset the magnetic field fluctuation when the current crosses zero, reducing vibration and noise.
2. **Contact Parameters and Materials**
- **Contact Capacity**: DC relay contacts have a lower voltage but stronger current capacity. For example, the DC contacts of the JTX series can switch 10A/28VDC, while the AC contacts are 10A/220VAC. In the HH52P series, the DC (DC-13) rated power is only 140W, while the AC (AC-15) reaches 1100VA.
- **Material Differences**: Both use silver alloy contacts (with a contact resistance ≤ 100mΩ). However, the contact gap of DC relays is larger. Some models (such as NJX-13FW) achieve "zero arcing" through sealed packaging, adapting to harsh environments.
III. Performance Parameters and Application Scenarios
1. **Power Consumption and Response Speed**
- **Coil Power Consumption**: DC relays have lower power consumption. For example, the power consumption of the DC24V model is about 0.9W, while that of the AC model (such as AC220V) is about 1.8VA.
- **Action Time**: DC relays act faster (≤20ms), suitable for PLC control that requires quick response; AC relays act slightly slower (≤25ms) but have better stability, and are often used in industrial machinery.
2. **Typical Applications**
- **DC Scenarios**: Automotive electronics (such as the JD1926A series), PLC control (NJX6 series), and circuits that require precise polarity. Attention should be paid to the correspondence between positive and negative poles during wiring.
- **AC Scenarios**: Power protection, automation equipment (such as HH53P used for motor control), and high-voltage environments, without considering phase issues.
IV. Selection and Usage Notes
1. **Voltage Matching**
- The coil voltage must be strictly matched. For example, connecting a 24V DC signal to a 220V AC relay coil will cause burnout.
2. **Load Characteristics**
- For DC relays, attention should be paid to the load type: inductive loads (such as solenoid valves) need to be connected in parallel with freewheeling diodes, while resistive loads do not require additional protection.
3. **Installation and Environment**
- For DC relays in low-pressure or humid environments, it is recommended to choose sealed models (such as NJX-13FW). For AC relays, attention should be paid to the ambient temperature (-40℃~+85℃).
V. Model Comparison Examples
| Parameter | HH52P-AC220V | HH52P-DC24V | NJX6-1Z AC277V | NJX6-1Z DC30V |
| Coil Voltage | 220VAC | 24VDC | 277VAC | 30VDC |
| Contact Capacity | 10A/220VAC | 10A/28VDC | 6A/277VAC | 6A/30VDC |
| Arc Extinguishing Technology | Natural zero-crossing + silver alloy contacts | Permanent magnet magnetic field arc extinguishing | Silver alloy contacts + optimized structure | Silver alloy contacts + sealed packaging |
| Typical Application | Motor control, power protection | PLC output expansion, automotive electronics | Industrial automation | Low-voltage DC circuits |
Summary
Chint small relays have significant differences between DC and AC models in structure, performance, and application. DC relays focus on polarity control and arc-extinguishing capability, suitable for low-voltage precision scenarios; AC relays emphasize stability and high-voltage adaptation, and are widely used in industrial environments. When selecting a model, comprehensive consideration should be given to the power supply type, load characteristics, and environmental conditions to ensure the reliable operation of the system.
