As a result of the changing and more demanding environment for duty of care and the need to make provision for the evacuation of disabled, injured or incapacitated persons from public premises. The Local Governments of the UK have embarked upon an initiative to provide purpose built standby power systems for emergency evacuation lifts to be installed in schools, libraries, hospitals, and other public buildings.

This EPS series of stand by power systems is designed to supply three phase and single phase motors and traction motor drive units of emergency evacuation lifts in an emergency or when the public power supply has failed.

The EPS standby power system is a fully self contained, free standing high performance rectifier battery charger and an inverter with secure bypass and change over feature. The EPS system is provided with a valve regulated or AGM lead acid 10 years design life storage battery sized to support the inverter load for an autonomy period long enough to permit 10 upward and 10 downward lift car journeys within the one hour period as stipulated in the British standard specification.

In normal mode the control logic of the power system is energised so the rectifier will maintain the battery in a fully charged condition. The battery charging function will automatically revert to standby when the battery is fully charged.

The power consumption of the EPS standby power system in quiescent mode and with the battery in the fully charged condition does not exceed 100 Watts.

The operational mode is by means of a local key selector switch with “local”, “remote” and “automatic” positions fitted to the control panel of the EPS system. The normal operational mode is in “remote” position connected to an externally located security key switch that will enable an authorised operator to take control of the lift and allow it to make the prescribed number of journeys.

If normal mains power is still available during the emergency use, the remote key control switch actuation allows the use of the mains power source and preserves the stored energy in the batteries.

If the mains should subsequently fail or if the mains power is switched off during the emergency evacuation process, the lift motor or traction drive system is automatically powered by the inverter using the stored energy of the battery.

The EPS standby power supply systems comply with BS EN 60146 and specifically designed for use with lift traction systems using single phase and three phase induction motors fitted with VVVF traction drive systems as supplied by OTIS, Schindler, KONE, Mitsubishi etc.

• The EPS20T in its normal mode has it’s internal logic energised by means of a local key switch like the ignition switch in a car. The rectifer logic is on and it keeps the battery charged, the inverter is switched off, the system is in "cold" standby.
• The lift traction system is fed through the bypass circuit of the power system and the power flow through the EPS20T will be shown on the LED’s in the small strip mimic panel on the front door of the equipment.
• The EPS20T system logic can be switched into the hot standby mode by means of the local key operated switch or by an external contact closure command from auxiliary terminals on the remote located emergency lift evacuation switch.
• This evacuation switch commands the logic in the EPS20T to start the inverter and it is then held in hot standby ready to power the lift traction equipment.
• The lift motor traction system and controller does not have a brain so it does not know if it is being fed from a mains power source or from the standby power system so we send it a “ready” signal as soon as the EPS20T is ready for duty.
• We also signal to the remote evacuation switch by means of a contact closure in the EPS20T that it is “ready for duty”, this signal is intended to illuminate a lamp adjacent to the remote evacuation switch.