High-voltage motors and low-voltage motors

Conventionally, it is divided into 200kw units, with some being 185kw; that’s basically it

It cannot be generalized; it depends on the industry. In the past, in industries such as lifting equipment and power plant auxiliary systems, things were handled according to the practices of various motor manufacturers – 750KW served as the lower limit, while 1200KW was the upper limit. Taking ABB motors as an example, high-voltage motors with a capacity below 750KW were basically custom-made. This is because both high-voltage motors and high-voltage frequency converters are quite expensive; it is not economically viable to use motors of too small a size for high-voltage applications. But nowadays, for port projects, the 250KW motors used in design institutes are all high-voltage types, with a current of only around 10 amperes. Perhaps it is due to the special nature of power supply and distribution in ports; currently, all cables are buried. For a current of 30A, 4×25 square millimeter cables are required, and this ratio is really too low. Moreover, equipment such as conveyor belts can be several kilometers long, and it is precisely this special environment that has given rise to such practices. As for the claim that high-voltage motors are not used abroad, that’s nonsense. Previously, 3KV voltage levels existed because high-voltage motors were only capable of operating at 3KV. With technological advancements, high-voltage motors can now operate at 10KV, which is why voltage levels such as 3KV for power distribution have disappeared. It’s clear that the problem with high-voltage motors has been resolved. Compared to low-voltage motors, they have extremely low wire losses, and their cables are much thinner; moreover, only high-voltage motors can be built on a large scale. Trying to make a 2000KW low-voltage motor? That’s just a joke. Overall, if the distance is short, within 100-200 meters, a conventional choice can be made, with 800KW serving as the dividing line ； In cases where the transmission distance might be particularly long, direct high-voltage starting can be used; a 250KW system can operate at high voltage.

Thank you for providing such detailed information based on your own experience. When I first started working, I encountered cooling water circulation pumps with a capacity of 400+ KW that used high-pressure systems; recently, in another department, there were also cooling water pumps with a capacity of 500 HP, but those used low-pressure systems. This led to some doubts, and after searching on Baidu, I found a wide variety of answers

We use high voltage for 160kw. With long-term operation, high voltage is of course more economical. But it depends on your power grid capacity configuration and distance. And whether to use an inverter.

JGJ 16-2008 Code for Electrical Design of Civil Buildings 3.4.2 When the total capacity of electrical equipment is 250kW or more, or the capacity of the transformer is 160kVA or more, it is advisable to supply power at 10(6)kV； When the total capacity of electrical equipment is 250 kW or less, or the transformer capacity is 160 kVA or less, low-voltage power supply can be used.