BENTLY 350092 136180-01 Series Protection Systems

Monitoring speed is essential in any automation process. The speed of any equipment driven by an electric motor can be due to a variety of reasons, for example. Overloading of transmission components, overloading, breakage, etc. In the case of open loop control, a speed monitoring device is useful to provide an AlRAM or “shutdown” of the motor. In the case of closed-loop control, for example. District of Columbia drive or V/F drive, feedback (4-20MA or 0-10V) is required to take corrective action.

Zero Speed Switches Speed drive sensors, also known as speed drive sensors, are used to detect stopping or unacceptably slow motion of a rotating shaft. Their application is generally in various machines, conveyors, power plants and industries involved in the production of cement, sugar, textiles, paper, etc.

BENTLY 350092 136180-01 Principle of operation.
The speed/motion of a rotating/moving object is sensed by a non-contact inductive sensor. The sensor probe is mounted on the sensing surface near the rotating object. Metal parts (flags) of specified dimensions should be mounted on the rotating object. When these flags pass over the surface of the detector, the front-radiated electromagnetic field of the detector is damped and then converted into corresponding output pulses.

BENTLY 350092 136180-01 is digital in nature and the circuitry is designed for operation in electrically noisy areas. However, the interconnecting cable should be at least 0.5 square grams. Hmmm. Size. The ALED provided at the rear of the detector provides a visual indication of the sensing flag. In the case of sensors other than inductive types, the pulses generated should be connected in the manner specified for individual sensors.

BENTLY 350092 136180-01 In order to monitor under speed conditions, a bypass arrangement must be in place at machine start-up. The output relay of the speed monitor is “closed” for start-up/speed conditions and “open” for normal operating speeds. Therefore, the relay contacts must be bypassed (overridden) during start-up. This can be achieved by using an external timer, by programming the PLC or by using the built-in bypass time delay (ITD).

With the built-in ITD function the output relay switches “on” to the “supply” condition and remains on until the specified time delay. If the device speed reaches a normal healthy speed during this period, the relay will continue to hold. If the speed does not reach the set value or when the speed drops below the set value it will run.