The selection of the high-voltage motor starter cabinet should in principle be greater than the capacity of the motor being driven. The rated capacity of the motor soft start cabinet usually has two nominal types: one is based on the power rating of the corresponding motor; the other is nominally based on the allowable current of the soft start cabinet.
The following two points should be noted:
1. According to the nominal capacity of the motor, the rated current of the products with different voltage levels is different.
2. The nominal operating capacity of the soft starter cabinet is nominal, and the rated capacity of the products with different voltage levels is different.
In addition, comprehensive considerations, such as the load capacity of the soft start cabinet, working system, environmental conditions, cooling methods, etc.
High voltage soft start cabinet
Need to increase capacity in the following cases
1. Soft starters or soft starters that use energy-saving control methods are often operated under heavy load conditions. It may cause the soft starter to overload, so the soft starter capacity should be increased.
2. The motor is used for continuous variable load or intermittent load, and the cycle is short. In this case, the motor is not allowed to run for a short time. Otherwise, the starter may be overloaded during operation, so the capacity should be increased.
3. The motor is used to repeat the short-time working system, and the cycle is less than the starting time interval specified by the manufacturer, which may cause the soft starter to overload during startup, so the capacity of the soft starter should be increased.
4. Some loads are too heavy, or the grid capacity is too small. When starting, the motor starts too long, causing the soft starter to trip. If the motor is not damaged, the capacity of the soft starter can be properly amplified.
5. For loads with special requirements on acceleration time, the length of motor acceleration time is a relative concept of inertia size. Some loads require a shorter acceleration time, and the motor's acceleration current will be larger. In this case, the capacity of the soft starter can be properly amplified.
6. The load with large inrush current during the transition process may cause overcurrent protection action, which can properly amplify the capacity of the soft starter.
The motor adopts direct start, and the starting current is 7 times of the full working current of the motor, which will cause excessive line voltage drop on the busbar, which will cause rapid and short-term voltage fluctuations in the power supply and busbar system connected to the motor, affecting the system. The normal operation of other electrical equipment. Therefore, the motor soft start cabinet is selected as the motor start control device.