Issues regarding relay wiring and the DO/DI points of DCS cards
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I have a question for everyone: In DCS systems, where the DO or DI points are powered by 220AC voltage, and these DO points are used to start motors through relays, how is the wiring done exactly? Should the DO signal be applied to the coil of the relay or to its contacts? How can a connection with 220V voltage be established? How can the coil be powered so that the relay contacts operate? Is it the power supply that is connected in series? http://img.co188.com/ivp/images/product/161/381/214/57240320.jpg
You need to learn a bit more about electrical appliances! Just knowing about instruments isn’t enough to understand things properly! The motor usually comes with three wires, in two sets: one set for starting and the other for stopping. The start wire is connected to the normally open contact of the relay, while the stop wire is connected to the normally closed contact. The DO signal controls the coil of the relay; once the coil is activated, the normally open contacts close, thereby sending a start signal. This causes the motor’s contactor to operate and engage in self-protection mode. After a few seconds, the start signal is discontinued and the motor begins to run. A signal indicating that the motor has started is sent back to the DCS as a DI signal, and the DCS then displays that the motor has been started. As for the starting voltage of the motor, that is, the voltage across the two wires of the normally open contacts, it can be either DC or AC – 110V or 220V, depending on the specifications set by the electrical equipment When it is necessary to stop the motor, the DCS sends out a DO signal; the relay connected to this stop signal then activates, causing its normally closed contacts to open. This interrupts the motor’s self-holding mechanism, resulting in the motor stopping, and the operation signal sent to the DCS disappears The DCS will display that the motor has stopped! Generally, there are local and remote switching switches on the motor’s local control panel; when remote control via DCS is required, indicators showing the standby status are available behind the DCS cabinet
In other words, we connect the DO signal directly to the coil of the relay; when the coil is powered, does that mean the signal from DO becomes charged? Are the contacts of the relay connected in series with 220AC? Thank you
The points generated by DO are usually equipped with protection, and there are also intermediate relays that serve as a isolation mechanism. The signal from DO is typically 24V; this voltage is used to control the intermediate relay, which in turn controls the energization of the coil! Whether the normally open and normally closed contacts of the relay are connected to 220AC depends on what the starting voltage of your motor is! There are both DC and AC types. I’ve seen ones with 110AC, 220AC, 110DC, and even 70DC! It’s different! It depends on the signal coming from the appliance! As long as it does not exceed the voltage rating of the relay!
The DO point DCS card can supply 24VDC power, directly controlling whether the intermediate relay is powered; the contacts of the intermediate relay then control whether the electrical contactor is powered, thereby determining whether the motor starts.
2nd floor: Can the contacts of a relay be connected to any voltage? I see that the supply voltage for the relays in DCS is 24VDC, while the electrical lines connected to the contacts are at 220VDC; there are also those at 220VAC. Does the difference in voltage of the electrical side signal wires (including start/stop and operating signals) impose any requirements on the DCS DO and DI relays? Thank you!
The DO output of the DCS is connected to the coil of the relay; the contacts of the (13–, 14+) relay (such as 9+, 5–) are connected to the electrical wires. When these contacts close, the electrical contactor maintains the signal, and the motor starts to operate.
The DO output of the DCS is connected to the coil of the relay; the contacts of the (13–, 14+) relay (such as 9+, 5–) are connected to the electrical wires. When these contacts close, the electrical contactor maintains the signal, and the motor starts to operate.
The DO output of the DCS is connected to the coil of the relay; the contacts of the (13–, 14+) relay (such as 9+, 5–) are connected to the electrical wires. When these contacts close, the electrical contactor maintains the signal, and the motor starts to operate.
The DO output of the DCS is connected to the coil of the relay; the contacts of the (13–, 14+) relay (such as 9+, 5–) are connected to the electrical wires. When these contacts close, the electrical contactor maintains the signal, and the motor starts to operate.