Husnen Rupani:
In this video, we will use a programmable relay to create a direct online circuit with DC injection braking. Let’s get started.

Hi, I’m Hus. In this video, we’ll use Zelio programmable relay to program a direct online circuit with DC injection braking using our control circuit and motor starter pracboxes. First, we will look at the circuit diagram, then we’ll connect the circuit, then we’ll look at the program that we’ve written, and then we’ll test the program with the circuit. Let’s start with the circuit diagram. This is the circuit diagram that we’ll connect in this video. Just a disclaimer, I’ve only made this circuit functional, so it might be missing a few things, but it will work as expected for our particular application.

Let’s identify all the components in this circuit first. Here’s our three-phase motor. This is our main contactor’s contacts and this is our main contactor. These are the contacts of our braking contactor and this is our braking contact coil. This is our stop button. We’re going to use both normally open and normally closed sides. And this is our start push button. And this unit here in the middle is the inputs and outputs of the Zelio programmable relay that we’ll use. Let’s understand how this circuit will connect because we have two different power supplies here. You can see that we’ve got L1, L2, L3 going through the contacts and to the motor. However, we also have a DC source here. So the DC supply is used for a couple of things. One is for the Zelio operation and the inputs and for the braking as well.

Let’s connect the circuit. We’ll start by wiring our control circuit to Zelio and then to the contactors and then after that we will connect our power circuit. So far we have connected our inputs. So we’ve connected our stop button that has NC and NO and our start button, which is just a normally open. The way we’ve connected is we’ve taken the 24 volts going inside the one side of the contacts and then the other side going to I1, I2, I3. Now, I1 is our stop button, which is normally close side. I2 is our start button, which is normally open. And I3 is our stop button, is normally open side. So these are our inputs. Now normally you would also connect the common, but in this pracbox the common of the Zelio is connected internally to this power supply, which has now completed our circuit. So we won’t have to worry about connecting the common wire. So the other thing we haven’t done is connected the 24 volts and common to the Zelio. That’s because it’s internally powered. So as soon as we power the box, Zelio will get power. Let’s continue our circuit.

So what we’ve connected here is the L1 going to Q1 and Q2. Now, Q1 and Q2 are the relay contacts. So we’ve connected that on one side. And on the other side of Q1 and Q2, we have connected our main contactor and the braking contactor. Let’s continue the circuit. We have now finished connecting our control circuit. We’re going to now wire our power circuit. We have now completed our power circuit as well. So just to see the flow, the three phase will go to our main contactor, come out of the main contactor, go to our three phase motor here. And the terminals of the motor will go to this side of our braking contactor. On the other side of the braking contactor, we have our DC supply connected.

Now that our circuit is complete, let’s look at our Zelio program and understand it. This is the Zelio program that we’ll download to our Zelio programmable relay to have our DOL plus DC injection braking operation. Let’s understand how this program works. So if you look at rungs one and two, that is basically our direct online circuit. So that’s our stop button. When the stop button is connected and normally closed, this will automatically close. When our start button is pushed, this will close and our main contactor will energize, closing this contact, giving us a holding circuit. Now, this will only operate if the brake contact contact is closed in this case, which means the brake contactor coil is de-energized. So that’s our interlock that we’ll use. So those two contactors can’t energize at the same time. What you might notice here is this TX and RX. I will talk about those … So those are messaging. I’ll talk about those after I’ve gone through the rest of the program.

So skipping rung four because that’s also messaging going to rung five. When the brake button is pressed, which is our stop button is normally open side, if we keep it pressed, then our timer will start timing. At the same time our brake contactor will energize. As our brake contactor energizes, we have the DC going to the motor. But we have to ensure that the AC supply doesn’t interact with DC. So to avoid that, we have our interlock here, which means that if the main contactor is operating, our brake contactor can’t come on. And as soon as the timer has finished counting down, this contact will open, which will then de-energize our brake contactor.

Now, that’s the working of the program. Let’s understand all the messaging that we have here. So there are four messages that we are using. The messages are motor on, motor off, motor is braking, and finally, the motor has stopped or motor stopped. The way that we’ll operate is when the main contactor comes on, we will say that energize motor on, but also reset motor is braking because we know that there is an interlock. We can’t brake while the main contactor is on. So that’s the message that will get displayed when the first rung is energized. When the main contactor is off, our final message, which is motor off, will be displayed. So that message will be there all the time. We’ve kept that there. That way we know that if the main contactor is off, we know the motor will be off.

The third message is motor braking, which comes on at this rung here. So this will display the message that the motor is braking. Now, that will only operate while the timer contact is closed, which means the timer is still counting down. Finally, when the timer has finished counting down, this rung will energize because our brake contactor will be off, which means this rung will turn on and this contact will close, showing that the timer has finished counting. The final message will show that the motor stopped. So that motor stop will be if we’re still pressing the brake button. And as soon as we let that go, this rung four message will get displayed, which says motor is off. Now let’s see how the whole circuit will operate.

I have already downloaded the program to the Zelio programmable relay and you can see that it’s showing motor off at the moment. What we’ll do, we’ll only turn on our L1. And since our control circuit’s powered through DC, the power is already there. We’ll keep the main power supply, which is the three phase, and the DC power supply off to see how our control circuit will work first. Then we’ll turn the power on and test the whole operation. When I press the start button, I’m expecting the main contactor to turn on and this message to change from motor off to motor on.

We can see that that the contactor is pulled in and the motor on message is displayed. If I momentarily press the stop button, we can see that the contactor disengaged and the message changed to motor off. If I press the start button again, the contactor is pulled in, motor on. This time I’m going to keep the stop button pressed, which will then turn on the brake contactor and change the message as well. Let’s see. That’s turned on, motor braking. As soon as the timer finishes, this coil disengages. It says motor stopped because I’m still pressing the brake button. As soon as I let that go, the message changes to motor off. So our control circuit works as expected. Let’s turn on all the power and test if the rest of our operation works as expected.

Okay, let’s turn on our motor. We can see that the motor is turning, motor on message is there. I’ll momentarily press the stop button to see what it does. We can see that the motor eventually coasts and stops and motor off is displayed. Let’s turn it on again. This time I will keep the stop button pressed to see if the motor brakes instantly. And we can see that that stopped instantly, motor braking. Coil disengaged so the braking has now stopped. Motor has also stopped. If I let that go, the message changes to motor off. So our circuit is working as expected.

I hope you enjoyed this video of DOL with DC injection braking using Zelio programmable relay. If you have any questions or feedback, please feel free to contact us. Thanks for watching.