Device for overload protection of electrical drives

摘要

In the case of electrical drives, particularly in the case of lifting motors of lifting appliances, such as block and tackle systems, cable winches, crane installations or lifting tables, overload protection is required. In order to create rapid and reliable protection of the electrical drive and hence also of the lifting appliances operated by it against overload with relatively little structural complexity, a circuit is proposed which measures the current and phase angle of the drive motor as a direct function of the torque of the drive motor and hence of the load during the drive process and forms a mixed load signal from this measurement. This mixed load signal is compared with an adjustable maximum value and switching contacts of output relays are opened if the maximum value is exceeded.