GeePlus Bistable Rotary Solenoids:
ideal for battery-powered applications or applications
where heat dissipation or radiated electrical noise are critical.
The bistable rotary solenoid from GeePlus (also known as magnetic latching or self-holding solenoids) is a line of rotary solenoids that take advantage of a high performance permanent magnet. The principle of operation is similar to all rotary solenoids:
When the coil is energized, the plunger moves toward the pole piece. This permanent magnet rotor can be energized for polarization in either magnetic direction. The advantage of the bistable solenoid is that, once plunger movement has occurred, the plunger willl remain in the end position without any further electrical power input. The ability to hold in either end position reduces power consumption and dissipates heat.
The ability to drive in either direction also eliminates the need for a return spring; the fully-developed torque is available to accelerate the load for fast operation. For fastest operation, a high-power pulse is applied to obtain maximum torque and speed; power to the solenoid is then cut and it holds the end position without any power being required.
Operation is described in relation to the picture and graph shown for a 2-pole device. In the de-energized condition the rotor will try to turn so that its magnetic poles are aligned with the stator poles.
When the rotor is turned away from this position, a torque is developed which tends to return the rotor to one of these two end positions. This torque increases initially as the rotor is turned further from the stable position, then decreases towards zero as it approaches the position P+ or P- midway between the stable positions. As the rotor passes through this position, the torque reverses direction and acts towards the other stable position.
In the energized condition, the rotor will try to drive towards the 90º position from any other angular position (the -90º position is an unstable equilibrium point where zero torque is developed).
How to apply the bistable rotary solenoid:
The description of how to apply the Bistable Rotary Solenoid relates to the illustration showing installed end-stop configuration. Dimension drawings for all BRS-series products show the part in the cental (unstable equilibrium) P+ position.
Two types of operation:
Bistable operation yields the fastest achievable cycle time. To operate in this way, the mechanical end-stops should be located an equal distance either side of the centre (P+) position. A forward current pulse will drive the device in a clockwise direction; a reverse current pulse drives the device in the counter-clockwise direction. In the de-energized condition the solenoid will remain in its current end position unless disturbed by an external influence.
Monostable operation defaults to a preferred position in the event of power loss to the system. Both end-stops are positioned to the same side of the center position as shown in the RH view. With no power, the solenoid will default towards the end-stop furthest from the center position. The solenoid can be driven electrically in both directions for fastest operation, or can be driven in one direction, and allowed to return under the influence of the residual field. In the latter mode the device can functionally replace other types of rotary solenoid. |
