Problems with using automatic transfer switch devices to control pumps!
Thread Content
Critical equipment is powered by dual power supplies, and automatic transfer devices are used to ensure that the motors continue to operate without stopping due to brief power outages during the transfer process. When selecting such devices, consideration should be given to the timing of the automatic transfer and the operating time of the motor’s AC contactors; it may be necessary to install additional devices, such as B-series AC contactors with a delayed shutdown function This post was last edited by mu99899 on 2008-1-25 16:27.]
The switching of the standby auto-transfer device involves not only the issue of contactor tripping due to loss of voltage. When the voltage at the motor terminal drops to around 60% of the rated voltage, the motor draws a large amount of reactive power, and its torque drops sharply. If the standby power source is connected when the residual voltage on the main bus drops below this critical value, it will **worsen the conditions for the motor to start on its own; in fact, the motor may fail to start, causing the standby power source to trip due to overcurrent and low voltage. Therefore, to ensure the continuity of the production process, a backup power supply should be activated before the critical voltage is reached. The automatic transfer switches available on the market today are unable to ensure a disturbance-free switchover between two power sources. There are systems described in literature that use a backup power source for continuation of operation, but it is unclear whether this technology is mature. For individual small-capacity critical loads, a delayed auto-start device or UPS can be installed to ensure uninterrupted operation. These are just my personal opinions; please correct or supplement them if they are incorrect.