Relay for monitoring the rotation speed of the electric motor RKS
Information about the speed of rotation of electric motors can be obtained from various speed sensors, as well as from the motor itself. The speed of AC and DC motors determines the magnitude of their EMF. Thus, if you measure the magnitude of the EMF, then this way information about the magnitude of the velocity will be obtained.
Relay for electromechanical speed control (RKS)
The electromechanical speed control relay (RKS) works on the principle of an induction motor. The relay rotor is a permanent magnet 1 connected to the motor shaft whose speed is measured. The permanent magnet is placed inside an aluminum cylinder 5 which has a squirrel coil. The cylinder can be rotated around the axis at a small angle and switched at the same time using the limiter 3 contacts 4 (6).
Schematic of the RKS speed control relay device
When the engine is stopped, the brake is in the middle position and the relay contacts are in the «normal» position.With the rotation of the engine and thus the magnet 1, already at low revolutions, a torque begins to act on the cylinder 5, under the influence of which it rotates and ensures with the help of the limiter 3 the switching of contacts 4.
When the engine speed is close to zero, the cylinder returns to the middle position and the contacts 4 go to the «normal» state. The switching speed of the relay contacts is determined by the position of the adjusting screws 2.
Speed control relays are useful for automating the braking process when it is necessary to ensure that the motor is disconnected from the mains after reducing the speed to zero, which is why the speed control relay is very often used in automatic braking circuits of squirrel-cage rotor three-phase induction motors by the opposition method.
RKS Speed Control Relay Specifications
Rated current of the contacts — 2.5 A. Rated voltage of alternating current on the contacts — 500 V. The maximum speed of the relay is 3000 rpm. Number and type of contacts — 2 switching