Status Alarming
The auxiliary contacts in a motor starter are commonly used to indicate when the 
motor is running. However, auxiliary contacts only indicate the position of the contactor, not the actual load status. If a downstream disconnect is open (for example, for maintenance) or the contact fails (either sticks or dirt build-up) there can be serious consequences.
At a large fish farm, failed aerator pumps resulted in massive stock losses. Because the auxiliary contacts remained closed when the pump failed, the alarm was never activated, the back-up pumps were not switched on and the fish suffocated due to lack of oxygen. Now NK Technologies’ Current Operated Switches have been installed to provide an alarm signal and a signal to automatically switch over to the back-up aerator pumps.
DC Motor Installations
Many applications requiring high torque at low speeds, like bridge cranes and log 
carriages, use DC shunt wound motors. Since it is relatively easy to control the speed of a DC motor by adjusting the voltage to the field windings, precise regulation is afforded to applications like printing press paper feeds or web control of multiple motors in the paper making process. Using an NK Technologies’ DC Current Transducer will provide an analog signal that can be used to keep the motor from over-current situations. Using an NK Technologies’ DC Current Operated Switch will insure that if the motor field supply is lost, the motor will not over-speed to the point of self-destruction.
Crusher/Grinder/Shredder Motor Interlocks
The performance of size reduction equipment like crushers or grinders can be optimized by controlling the in-feed in order to:
- Help prevent jamming
- Improve the uniformity of the resultant product
- Enhance overall production efficiency
By installing an NK Technologies’ Current Transducer or Power Transducer to monitor the in-feed to a crushing process, the speed of the in feed drive can be slowed when the crushing motor is working too hard, or the speed can be increased when the crusher is under worked. The analog 4-20mA proportional signal is fed directly into a VFD, and the drive does the rest of the control.
Additionally, NK Technologies’ Current Operated Switches installed on other conveying motors can be used to signal malfunction (for example over-load or motor failure) to help prevent costly equipment damage.
NK technologies current sensors come in a variety of configurations for quick and simple installation either for the OEM or End-User.