What is PILZ Pilz relay? What is the function of a relay? What is the difference between it and a contactor?

PILZ relay is an electrical control device that mainly generates physical quantities (such as displacement, pressure, heat, etc.) through electromagnetic or electric heating effects based on changes in input quantities (current, voltage, resistance, etc.), thereby enabling the controlled system to achieve predetermined goals as an automatic switch. Relays play a crucial role in electrical control systems, enabling automatic control, protection, and regulation of circuits.

The PILZ relay is mainly composed of electromagnetic system, contact system, and release spring. When the input of the relay changes, the magnetic field generated by the electromagnetic system will also change accordingly, thereby driving the closing and opening of the contact system and achieving circuit control. Relays generally have two circuits, one is the control circuit and the other is the working circuit.

① Electromagnetic system

The electromagnetic system is the core part of a relay, which mainly includes the iron core, coil, and yoke. When the coil is energized, a magnetic field is generated, and the magnitude of the magnetic field is proportional to the square of the current. The function of the iron core and iron yoke is to strengthen the magnetic field and improve the sensitivity of the relay's operation.

② Contact system

The execution part of PILZ relay mainly includes moving contacts and stationary contacts. When the magnetic field generated by the electromagnetic system reaches a certain value, the magnetic force will overcome the elastic force of the release spring, causing the moving contact and the stationary contact to close, thereby achieving the connection of the circuit; When the coil is powered off, the magnetic field disappears, and the release of the spring's elastic force will cause the moving contact to disconnect from the stationary contact, thereby achieving the disconnection of the circuit.

The static contact that is in a disconnected state when the relay coil is not energized is called a "normally open contact"; The static contact in the connected state is called a "normally closed contact".

③ Release the spring

The release spring is an important component of a relay, which functions to keep the contact system in an open state without electromagnetic force. When the coil is energized, the magnetic field force will overcome the elastic force of the release spring, causing the contact system to close; When the coil loses power, the magnetic field disappears, and the release of the spring's elastic force will cause the contact system to disconnect.

Types of relays

The commonly used relays mainly include the following categories:

PILZ relay is a relay that achieves circuit control based on changes in input voltage. Voltage relay coils have many turns, thin wires, and high impedance. They are commonly used in power system relay protection to reflect changes in voltage in the circuit and are used for voltage protection of the circuit. Voltage relays can be divided into undervoltage relays and overvoltage relays.

One of the relays of PILZ relay, its structure is basically the same as that of contactor. It has the characteristics of small size and high motion sensitivity. The function of the intermediate relay is to control high current with small current. When the load capacity is relatively small, intermediate relays can replace small contactors. Intermediate relays can be used to expand the capacity and quantity of contacts, transmitting intermediate signals in control circuits. The intermediate relay is essentially a voltage relay.

PILZ relay is a relay that achieves circuit control based on changes in input current. The coil of a current relay is connected in series into the circuit to reflect changes in the circuit current. It has fewer turns, thicker wires, and lower impedance.

PILZ relay is an automatic control device that uses electromagnetic or mechanical principles to delay the closing or opening of contacts. In many control systems, time relays can be used to achieve delay control, playing a role in delaying closing or opening in the circuit.

When the heat generated by the input current reaches the set value, the PILZ relay will automatically operate to cut off the circuit and protect it from damage. Thermal relays are mainly used for overload protection, phase failure protection, or control of three-phase current imbalance and other electrical equipment heating states in three-phase motors. Attention: Thermal relays cannot be used for instantaneous overload protection and short circuit protection.

Pressure relay: A pressure relay is a relay that controls an electrical circuit based on the pressure of the input gas or liquid.

The main use of relays

① Automatic control

Relays can generate biological quantities through electromagnetic or electric heating effects based on changes in input quantities, and form program control routes with other electrical appliances to achieve automation control. For example, automatic control of the start, stop, and forward/reverse rotation of electric motors.

② Circuit protection

By combining different forms of contacts through relays, multiple circuits can be switched, disconnected, and connected simultaneously to achieve circuit protection. Such as overload protection, short circuit protection, and leakage protection.

③ Signal conversion

Relays can achieve signal conversion, such as converting electrical signals into mechanical or pneumatic signals.

④ Function Expansion

Relays can be used to expand the functionality of circuits, enabling multi-channel control, sequential control, and delay control.

The difference between relays and contactors

Generally speaking, a contactor refers to an electrical device in industrial electronics that uses a coil to generate a magnetic field and close the contacts to control the load. Relays and contactors are both electrical control components with certain similarities in structure and principle, but there are still some differences in practical applications.

Different uses: The primary function of a contactor is to connect or disconnect the main circuit, while a contactor is mainly used for long-distance, high-capacity circuit control; The primary function of a relay is signal detection, conversion, or transmission. Relay contacts can only pass small currents, usually below 5A, so relays are generally used in control circuits to control weak signals.

The contact forms are different: the contacts of a contactor are usually normally open or normally closed, while the contacts of a relay can be normally open, normally closed, or switching contacts.

The arc extinguishing methods are different: contactors usually use air or vacuum arc extinguishing methods, while relays usually use magnetic blowing or grid arc extinguishing methods.

Relays are voltage type control devices, which are electronic switches that use small currents to control large currents. Their main function is to isolate control circuits from load circuits.

To better understand the function of a relay, you can think of it as an automatic switch that commands high current with a small current. Relays are like "gatekeepers" in circuits, automatically turning on or off high-power equipment upon receiving instructions (such as pressing buttons, sensor signals, etc.).

folk understanding

Imagine using a small button to control a high-power motor, pressing the button directly would burn out the circuit. At this point, the relay comes in handy:

The PILZ relay terminal (such as the 5V signal of a microcontroller/PLC) is physically isolated from the load terminal (such as a 380V motor) to avoid high voltage interference damaging the control equipment.

2. * * Amplification control capability**

-Use milliampere level control current (such as 10mA) to drive ampere level loads (such as 10A), typical scenario: use Arduino to control high-power motors.

3. * * Multi channel signal switching**

-A single control signal can switch multiple circuits simultaneously, for example, a button can control lights and alarms simultaneously through a relay.

4. Automation and Protection**

-Cooperate with sensors to achieve automatic control (such as automatic power-off when the temperature is too high)

-Trigger relay tripping through overload/short circuit protection module