How to choose a motor for starting
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Which expert knows which motor power level requires a high-voltage start method, or should it be started directly? Several of the circulating water pumps in our company are 450 KW in capacity. Is it feasible to use 380 volts? Should I just choose a 10,000-volt high-voltage motor?
First, the poster needs to determine the voltage category of the motor’s power supply – whether it is 380V or 10,000V. Regarding such issues, one must first consider the capacity of the factory transformer (i.e., the size of the system capacity); this is mainly a theoretical approach, as it isn’t very practical in reality； It is recommended that the poster opt for high-voltage starting, mainly for the safety of the power grid, as this can reduce the impact on it.
There is 10kv power in the factory, as well as low-voltage power. I mainly want to ask if there are any relevant standards or something like that.
If you need to consult standards, you can refer to petrochemical standards! According to petrochemical standards, for motors with a power of 160 KW or more, medium-voltage motors (6 KV and above) are recommended. If the owner is not in the petrochemical industry, low-voltage motors with a capacity of 250KW or less can generally be considered. Above this power level, the current in the motor is higher, which requires more stringent specifications for the cables, and its operational reliability is not as good as that of high-voltage systems ； Of course, if your company has a 690V (IEC standard) system (referred to as 660V in China), then the motor power can reach 315KW, which would result in lower investment costs.
Based on my nearly 20 years of experience in AC speed control projects, the supply voltage for frequency conversion motors is usually selected according to the following criteria: 1. For fans and pumps: ≤250KW, Ue=400V； >250KW & 1000KW: Ue=10KV. 2. In applications such as rolling mills and paper manufacturing where high-precision speed control is required, the capacity is usually large, and the supply voltage is Ue=1100V/3300V/6600V. This arrangement is determined by investment and operating costs. Of course, for a specific project, it is necessary to apply flexible judgment based on the actual circumstances!