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Dear Che, What I meant with transition delay is the delay between opening of the star contactor and the closing of the delta contactor.

Dear marke, It is indeed that the full speed current in Star is in the order of 30s Amps. However, I'm concerned with the starting current that could increase as high as 200 Amps, that the contactor would get damaged because its rating for continuous Amps is only 105 A. The high current doesn't...

Dear Marke, As I've previously mentioned, it had been done before when the transition delay was set at 1.6 seconds. However the contactors broke down in just about a little more than a month. And since the star contactor broke down first, I guess the problem is not just the arc, but...

Dear Marke, Thanks for the explanation. Based on that, I assume the problem is actually the arc when switching the contactor. If that's the case then, what do you think is the suitable solution to make sure that the arc has been extinguished before the other contactor closes?

Dear Bill, I'm not sure I know what you mean with grape. But here is the burn marks that I was talkig about.

Dear Lionel, It reached full speed in star mode

Dear Che, My arguments for buying the SN-220 is because the peak current for both the star and delta contactors after I've measured it is about 165-200 amps. Thus, I figured that if I buy the SN 220, which has a rated current of 220 A, there would be no more welded contactors. The thing is, I...

Dear all, Thank you for all of the feedbacks. I have one other question. So, I have done plenty of experiments using the same loads with the same machine and by using new contactors(but the same type). The motor was able to reach full speed in less than 4 seconds, so I guess nothing is wrong...

Dear lionel Thanks for the advice. I do believe so, that the culprit is because of the contactor is undersized. However, I'm struggling to find the right size. So about the AC -4 contactor, what should the rated current be? should it be at least the same with the FLA of the motor? Thanks.

Dear Bill, Apologize, I just realized the current on the delta side is larger😂. Okay I understand now. The motor is used to mix paint, a very high density and viscosity paint. When the machine is mixing lower viscosity and density paint, there were no problems with contactors. But when it mixes...

Dear Che, Thanks for the insights and advice. and about the schematic. I'm afraid we don't have one. However, I would try to draw it from scratch.

I think I was mistaken. It is not by changing the voltage to change the speed, but by adding resistance

Dear Waross We change the speed by adjusting its winding to change its voltage, hence, its speed.

Dear Che, Here is the damage on the contactor. I'm not sure what causes it, overheating or short ciruit. What certain is that the star and delta contactor is both melted, making them unable to open. My best guess is that the star contactor got burnt when starting, causing it to fail to open. So...

Dear Lionel Could you please explain a bit about the 95% speed. Is it 95% of rated speed or 95% of any speed of the motor?(Because most of the time, the motor started at low speed, about 200 or 300 rpm from rated 1000 rpm, we change the speed by changing the motor tap). Also, could you give me...

che12345 Dear Che, the main contactor has the same rating with the other two contactors, and it's also AC-3 rated. However, I don't understand about the contactor's coil voltage. Is it different with the main voltage? The contactor I mentioned is this.

RRaghunath Yes, I checked the starting current, which only about 165 A when the load is light. The speed when the star is open is about 800 rpm of full speed 1000 rpm. I haven't checked the current yet if the load is heavy because the management currently doesn't allow it(The contactors got...

Hello I have a 45 kw induction motor with starting method using star delta method. The star and delta contactors of the motor have been for several occasions got burnt. However, I haven't figured out why the contactors got burnt. The FLA is 93 A, and the contactors have a rating current of 105...