1.Structural features and operating principle 
This type of holdback is located using a bearing in which several shaped wedges are arranged in the raceway formed by inner race and outer race in a certain pattern so that it operates stably, the outer race is connected with two end covers, while the end covers are connected with the antirotation arm into an integral part through pins and the antirotation arm is limited by the fixed antirotation seat. When the motor operates normally, the holdback makes the wedges deflect by a certain angle through mechanics principle using the special geometry of the wedges so as to be in light contact with inner and outer race, thus reducing the coefficient of friction and improving the service life of the holdback. When the main motor needs to be shut down, the inner race of holdback reverses under the action of gravity of elevated material to drive the wedges to deflect and bring the inner race and outer race of the holdback to be wedged into an integral part so as to effectively prevent the motor from reversing. Therefore, this type of holdback is the most ideal non-reversing protector for conveying equipment such as large belt conveyor, bucket elevator etc. 
2. Service environment
The ambient temperature for holdback operation is -20~50℃, when the holdback is running, it will generate certain heat, so the ambient environment should be well ventilated, the temperature of the holdback running at allowable highest speed can reach 80℃, in this case it is required to check the effect on the motor equipment and take appropriate temperature reduction measures, if necessary. When the ambient service temperature exceeds 38℃ or when it operates in open air, effective protective measures should be taken (for example, use ventilating equipment or cooling equipment etc.). Around the holdback it is not allowed to place corrosive chemicals for fear of damaging the holdback seal
3.Model designation of the holdback
Example: NJD holdback with clockwise rotational direction of inner race, the specification of 130 and the installation hole diameter of 200mm; the model is NJD130-S-200.