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Atwell International Limited
The VG Overspeed Governor (VG OSG) is designed to be installed with new
lifts and retro fitted to existing passenger and goods lifts and when used in
conjunction with other VG Safety products such as the VG Safety Gear and or the
VG Rope Brake will provide a complete solution to the requirements of EN81-
20/50:2014. It can also be used with other “CE” marked safety products, but the
responsibility lies with the lift designer to ensure correct operation.
The VG OSG connects to the main lift control panel via its own specific control
box (VG OSG – CB01). From here it can receive power and signals to tell if the lift
doors are open, the state of the main motor contactor and the condition of the
main safety circuit. It also sends signals to the lift, warning the lift controller if the
lift speed reaches 110% above the normal running speed (Alert Signal) and will
operate the “CE” marked braking means in the event of overspeed or unintended
car movement.
The system will always deploy immediately and interrupt the main lift safety
circuit, if overspeed is signalled, unintended car movement away from the
landing with the landing door not in the locked position and the car door not in
the closed position or if the emergency stop button on the front of the control
panel (VGOSG-CB01) is pressed.
The governor incorporates a bi-directional drop-jaw mechanism which is
monitored by state of the art electronic sensors and operates by releasing a
12V dc electro-magnet in the event that either overspeed or unintended car
movement is detected, or the emergency stop button pressed.
When either overspeed or excessive unintended movement is detected the
governor will be activated which in turn will deploy the brakes under its control
and in addition to this an emergency stop signal will be sent to the main lift
control panel, by means of interrupting the main saftey circuit.
There are other functions included as standard with the system such as:
indictaion of status to assist with fault finding, remote reset and the ability to
bypass the Unintended Movement monitoring but still maintaining overspeed
detection. Other functions allow for a Test speed of 0.63m/s mechanical trip and
0.63m/s electrical trip (or trip speed if this is lower) to be selected and a hand-
winding function which will lower the overspeed trip to 0.3m/s.
Power loss is catered for by the incorporation of an internal battery back-up
system to seamlessly switch from mains power to battery and back again
without the need for manual intervention to reset the VG OSG. But if during the
power loss excessive movement occurs, or that the over speed governor trips,
a full reset will be required but this is done using a key switch mounted on the
front face of the VGOSG – CB01A control box.
If during its normal operation the system develops a fault then an error or alert
signal will be sent requesting the lift stops at the next floor and when the doors
opened the VG OSG will activate until the fault can be rectified by a competent
person.
Overview
