PLC power supply system reliability design - Database & Sql Blog Articles

GW MB10F 0.8A 1000V rectifier bridge

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

High-power led 1W red light imitation lumens led Sanan 30mil gold wire copper bracket 40

1. Plc power supply design In general, the basic power supply of PLC generally uses ACIOOV/240V and DC24V.
When the PLC ACIOOV/240V power supply is used, the input power supply voltage is usually allowed to fluctuate from -15% to +10%. For example, when the rated input voltage is AC100V, the input voltage is usually allowed to vary from AC85 to 110V. When the rated input voltage is AC240V, the allowable range is AC200-AC264V. The PLC requires a low frequency for the external AC power supply. The allowable frequency variation range is usually ±3 Hz. That is, when the rated input frequency is 50 Hz, the allowable input frequency varies from 47 to 53 Hz. When the rated input frequency is 60 Hz, the allowable The range of variation is 57 to 63 Hz.
When the PLC uses the DC24V power supply, the input voltage is generally allowed to vary from 15% to +20% (ie, DC20.4 to 28.8V, such as SIEMENS PLC), and some PLCs can reach -35% to +30% (ie, DC15). .6~31.2V, such as Mitsubishi Q series PLC). Compared to other computer control systems, it has relatively low input power requirements and is often easy to meet.
However, in order to ensure the normal operation of the PLC and suppress the line interference, in principle, for the AC 100V/240V power supply PLC, an isolation transformer, a surge absorber or a voltage stabilization measure should be added to the power input circuit. The PLC input power supply should be separated from the equipment power supply, AC control loop power supply, and AC output power supply, and have an independent protection circuit and a separate isolation transformer.
For DC-DC24V-powered PLC, in principle, it should be powered by a regulated power supply: at least three-phase bridge rectification and filtering should be used for power supply; generally, the DC power supply that only uses single-phase bridge rectification cannot directly supply power to the PLC. The PLC input power supply should be separated from the equipment DC power supply, DC control loop power supply, and DC output power supply, and have independent protection loops. When the windings are more complicated, the PLC should be powered by an independent regulated power supply.
When the system adopts a modular structure, the capacity of the power module should ensure that the power requirements of the PLC system are met. The rated output capacity of the power module should be greater than the sum of the power consumed by all the components in the system, and 20% to 30% is reserved. The balance.
2. 1/0 device external power I/O external power refers to the power supply for the PLC source input module, PLC output module, input sensor (such as proximity switch, etc.) and output actuator.
The external power supply for the PLC input signal is typically DC24V. Since the voltage fluctuation of the input signal may directly affect the change of the PLC input state, it is required to be high. In principle, it should be powered by a regulated power supply; at least it should be powered by three-phase bridge rectification and filtering; Single-phase bridge rectified DC power supply to prevent input signal sampling errors.
The external power supply for the PLC output signal and the output form of the PLC are related to the load requirements, which can be either AC or DC. Especially when using relay contact outputs, the power requirements are completely dependent on the load.
Normally, the PLC requires less output power than the input power. For example, for DC 24V intermediate relays and solenoid valve loads, a single-phase bridge rectifier DC power supply can generally be used. However, when the output of the PLC needs to be input to other control devices of the system: CNC, etc., it must be based on the latter. The requirement is to select the output power.
3. The design of the total power supply system of the PLC main power supply system must be analyzed according to the nature of the control object, technical requirements, system composition, and environmental conditions. The hardware design example of the PLC control system is given later in this chapter. reference.
As the basic design principle of PLC total power supply system, we should pay attention to the following aspects:
1 In the system, all power supplies related to the PLC can be disconnected through the total power switch of the equipment to achieve isolation from the power grid.
As the main control device of the system, 2PLC should be put into operation immediately after the total power supply of the equipment is turned on, without any other start-up operation, so that the control system can effectively monitor the control object.
3 For the control system that uses the basic unit and the expansion unit at the same time, the power of the expansion unit should be turned on before the basic unit or at the same time, so that the basic unit can effectively monitor the expansion unit.
4 The external power supply for the PLC input signal can be shared with the PLC basic power supply, but independent protection devices (such as circuit breakers, etc.) must be installed in the circuit.
5 When the external power supply for the PLC input signal is set independently, this power supply should be put into the work immediately after the total power supply of the device is turned on, so that the PLC can effectively monitor the current state of the device through the input signal.
6 External power supply for PLC output signal, can be shared with input power or independently set. For control systems with complex components and many actuators, multiple power supplies can be set as needed.
7 When the PLC output uses a common external power supply, multi-channel protection (such as circuit breakers) should be classified according to the different output objects, and the power-on sequence of each type of output should be different. The design shall ensure the on/off of various types of output power of the PLC, and be constrained and controlled by the "interlocking" condition of the high-voltage control loop.
8 For other control loop power supplies in the system, when the voltage is the same (such as DC24V control loop), it can be shared with the PLC input or output power, but must be installed with independent protection components (such as circuit breakers, etc.).