Application characteristics of EPS emergency power supply with motor load
EPS emergency power supply can be divided into different types according to different load applications, including special lighting and special motor load. The following is to introduce the EPS emergency power supply with motor load, what are the application characteristics in the process of use.
First of all, we need to understand the starting mode of the motor, in fact, the starting mode of the motor has frequency conversion, soft start, star triangle start, when choosing EPS emergency power supply products, the requirements and application characteristics are also different.
(1) The motor “hard start” working mode is adopted, and the selection scheme for this EPS output power is the same as described in 2.2. The advantage of this scheme is that the EPS emergency power supply can ensure the continuous operation of the motor when the mains power supply is interrupted or when the mains power is restored to normal work. The disadvantage is that a high-power EPS emergency power supply needs to be selected, and the cost is high.
(2) Select motor special EPS with frequency conversion start function
When the mains supply is normal, it supplies power to the motor load through AC bypass and transfer switch. At the same time, the mains power is also charged to the battery pack by the charger. When the mains power supply is interrupted, in order to ensure the safe operation of EPS, it is hoped that he performs the “delay switching” operation, so that the motor stops rotating completely and then starts the inverter, which performs the operation of frequency conversion starting from 0~220Hz and gradually increasing (starting time is a few seconds) for the following motor. The benefits of using the variable frequency start-up scheme are:
1) To prevent the potential clapping hazards caused by the EPS emergency power supply and the self-excitation power supply generated by the motor in the “inertial motion state” in the “non-synchronous lock” state of each other;
2) Can reduce the output power of EPS emergency power supply and reduce investment costs. At this time, the output power of EPS only needs to choose 1.2 to 1.4 times the rated power of the motor to meet the requirements.
The disadvantages are:
1) The user’s motor load is required to stop first, and then “frequency conversion start” at full speed, resulting in “discontinuity” of the motor load work.
2) If the following several motors need to carry out “time-sharing start” operation at different times, you may encounter such technical problems: When starting the motor in a static state, if the output power of EPS is large enough, it may withstand the impact of 5 to 10 times the motor starting surge current. Otherwise, it will force the EPS emergency power supply to re-enter a new round of “frequency conversion start” working state. One of the problems caused by this is that the motor that was originally at the normal working speed will be transferred again to the variable speed starting stage from 0 to 50Hz, which will bring trouble to the user’s work.
When the user chooses the EPS emergency power supply for the load of the motor, he must first determine the starting mode of the motor, and the EPS technician will make a matching solution according to your equipment, so that the entire emergency system will be more safe and reliable.