To control the sequence of operation of electrical devices, a time relay with a 220 V off delay is used. After turning on the electrical device, after a specified time, the load is disconnected. Thus, the sequence of operation of the elements of the electrical circuit is regulated and electrical appliances and technological processes are controlled.
Content
- Relay types
- Using timers
- Plant characteristics
Relay types
All relays are subdivided into galvanically isolated and non-galvanically isolated devices. Galvanic isolation refers to the electrical isolation of circuits in relation to other circuits in the vicinity. There is complete isolation between the control circuit and the controlled circuits.
In practice, the following devices are used:
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Devices based on the electromagnetic principle. Designed to work in DC circuits. A separate short-circuit is added to the coil of the device. Due to the residual magnetic field, there is a deceleration for releasing or closing the contacts. Regulation limits - up to 5 seconds. - Devices with pneumatic deceleration. After a signal is received, the armature cannot turn on the contact while the air is in the damper. The delay time is set by adjusting the hole. The delay is possible up to 60 seconds. The pneumatic time relay can be used to control metal-cutting machines or for stepwise regulation of acceleration and deceleration.
- 220 V turn-on delay motor relays are used to delay time from 10 seconds to tens of hours. They consist of a synchronous motor, gearbox, electromagnet and contacts.
- The devices on the clockwork are adjusted by means of a spring charged by an electromagnet. The relay contact is activated only after the clock has counted down the time. Before the advent of electronic relays, clockwork was widespread. They are distinguished by simplicity of regulation, accuracy of timing and easy readjustment.
- Electronic time relays with a turn-on delay are used when switching low-inductive or non-inductive loads. Energy savings can be achieved by using an electronic relay. It can turn off lighting in entrances and corridors after a certain estimated time, which is enough to leave the room.
Electronic timers have high accuracy, but their delay interval is much shorter than that of electromagnetic ones, and they require programming. Electromagnetic devices are less expensive and easier to set up. They do not require maintenance, but their resource of work is limited.
Using timers
Time relays can be divided into built into appliances and purchased separately. In multicooker, washing machine and dishwasher, the timers are programmed and cannot be influenced. You can independently use separate timers that control lighting, heating, door opening. The most common are digital timers, which are based on a quartz resonator with a stable frequency.
Replacement of human labor when operating various mechanical devices, increasing productivity devices without human intervention, increasing the safety of production - these tasks can be performed by relays time.
Plant characteristics
The characteristics determine the possibility of using devices in certain working conditions. The properties of time delay settings have four directions:
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Delay time range. It can be regulated within wide limits. - Stability of work. This parameter refers to electronic devices and characterizes the ability of the device to function when the supply voltage changes.
- Durability measured in on-off cycles.
- Electronic devices are characterized by power consumption.
Each timer is characterized by certain parameters. The algorithm of work is important, namely the sequence of switching on and off.
The most commonly used algorithms are:
- Turn-on delay - after the timer is powered up, the output pulse is generated after the set time has elapsed.
- An impulse is generated when the timer is turned on - the signal appears at the moment the timer is powered on and disappears after the set time has elapsed.
- After turning on the power supply of the timer, the output signal appears at the moment the control signal is removed and disappears after a set time.
- Delay off after power outage - the output signal appears when the timer is powered on and disappears after the set time after power off.
- Cyclic mode - after turning on the power supply of the timer, the pulse time alternates with the pause time and so on until the power supply is turned off.
In order to connect the timer, you need to know in which network it will be mounted - single-phase or three-phase. It is important to consider what this timer will commute, what load needs to be turned off or on. Using this data, you can select a device with the required characteristics.
