About soft starters

Firstly, according to what you’ve said, it certainly can’t be due to the starting current; the starting current during soft start is at most 5 times higher, so it definitely won’t reach 800A. In your case, the current increases under normal conditions, which suggests that there’s a problem with the fan itself—things like a lack of oil in the fan, increased resistance leading to overload, or issues with water ingress can all cause an increase in current. This is just a beginner’s opinion; please bear with me

I need you to confirm whether it’s the fuse core that has melted, or if it’s just a simple fuse blowout, or perhaps the conductive tabs at both ends of the fuse have oxidized and caused an arc discharge. Core melting indicates that a very high current was encountered momentarily ； The fusing at the connection of the two conductive plates indicates that the manufacturer did not handle the welding of the internal fuse to the conductive plates properly; over time, oxidation occurred and eventually led to fusing. However, its soft-start protection performance is excellent; it’s impossible for the fuse to blow, unless there is a fault in the soft-start mechanism or no protection is in place. Therefore, it can be concluded that there is a higher likelihood that there is an issue with the insurance itself. However, the original poster didn’t specify whether the system performed a soft start when the current reached 300A, or whether the fuse blew and caused the system to stop

Reply to 3# Baghdad: It wasn’t due to a soft start; rather, the current during operation exceeded 300A for about 1 minute, which caused the fuse to blow. Subsequent inspection by the maintenance team revealed that the bearings were seized. What I want to know is why the current was only over 300A – why did the 800A fuse still blow?

There are problems with the insurance itself, which is quite common; besides, that insurance policy must have been in use for over a year, right? After replacing it, check the other two carefully as well; if parking is significantly affected, it’s best to replace them too.

Reply to 5# Baghdad: There’s so much to talk about! I’ve only been working for a little over a year, so I don’t know much about it! Thank you

The main reason for the breakdown of this marine battery is bearing seizure, which is equivalent to the motor stalling. In such a situation, the current flowing through the motor is very high; even the minimum stall current can be around 3 times normal. If the bearing damage is severe, the value could potentially reach the motor’s starting current. For ordinary motors, the starting current is usually 6 to 7 times the rated current; for a 132KW motor, the stall current will definitely exceed 800A, and the phase with the highest current is likely to be the one that causes the fuse to blow first. Therefore, modern motor controls no longer use fuses; instead, automatic air switches are employed for quick shutdown in the event of a short circuit. This prevents phase loss in the motor, which could otherwise lead to motor damage. Additionally, when starting with a soft starter, the current may exceed 800A. But it certainly won’t reach 7 times; it usually ranges from 3.5 times to 4 times. During a time period of 1 minute like this, the soft starter should not be in operation but rather should operate in bypass mode; otherwise, the soft starter’s protection mechanism should activate. That’s why insurance can blow up.

Reply to 7# qhwangyz: Thank you, I understand. So what kind of circuit breaker do you mean by a quick-acting air circuit breaker?

This type of circuit breaker is not called a quick-acting air switch, but rather an automatic air switch. You can understand it by first reviewing the information on the operating principle of such air switches!

Support for the third floor...........

It also supports floor 7..................... Thank you for your guidance; I’ve learned something new today