Power Systems International And Cambridgeshire County Council Develop A High Efficiency Power System For Emergency Evacuation Lifts
Unlike the conventional concept of uninterruptible power supply (UPS) systems where the losses of a 20kVA system can be as high as 2 kilowatts this EPS system has losses of only 50 watts in its quiescent mode of operation. Making it a low energy consumption product and offering excellent ‘green’ credentials.
The EPS series of stand by power systems is designed to supply three phase VVVF traction motor driven hoisting units of emergency evacuation lifts in a premises evacuation emergency or when the public power supply has failed.
The standby power system is provided with a valve regulated or AGM lead acid 10 years design life storage battery with sufficient capacity sized to support the inverter load to permit the lift to make 10 upward and 10 downward journeys within the one hour period as stipulated in the EN-British Standard specification in an emergency situation. It is constructed in a compact dimensioned steel enclosure containing a high performance rectifier battery charger, maintenance free battery and an inverter, automatic bypass and logic controlled by a local or remote key switch.
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 normal operational mode is in “remote” position and permits the EPS to be enabled from an externally located “emergency power” control switch usually installed adjacent to the call button for the lift or on the control panel in the lift car so that an authorised person may take control of the lift to make the prescribed number of journeys. This remote “emergency power” control key switch may be supplemented by other parallel connected key switches sited close to the normal lift call button stations on landings to be used if the lift doors are closed and if access to an “emergency power” control switch inside the lift car is not possible.
The system is supplied with a wall mounting wrap around bypass unit that should be inserted by the electrical contractor into the mains power circuit feeding the lift traction system. This mechanically operated wrap around bypass unit is fitted with a rotary handle operated changeover switch, input and output plugs and sockets and should be installed close to the intended location of the EPS unit.
The EPS standby power supply systems comply with BS EN 60146 and are specifically designed for use with lift hoisting systems fitted with VVVF traction drives and three phase induction motors as supplied by OTIS, Schindler, KONE, Mitsubishi, Oakland etc.
The product can also be supplied for the hydraulic lift hoisting mechanisms using three phase induction motors and for lift hoisting systems with reverse energy recovery, load resistors and braking systems.
Summary points:
- The EPS20 in its normal mode has its internal logic energised by means of a local key switch like the ignition switch in a car. The rectifier logic is on and it keeps the battery charged, the inverter is switched off, the system is in standby
- Power for the lift traction system is fed through the bypass circuit of the EPS, the power flow through the EPS20 will be shown on the LED's in the small mimic panel on the front door of the equipment
- The EPS inverter is of an advanced PWM technology design using IGBT power semiconductors oversized to handle the harmonics produced by VVVF traction drives.
- The inverter overcurrent capacity enables the EPS to trip circuit breakers and rupture fuses using only the battery power source whereas an inverter in a conventional UPS system of the same kVA rating as the EPS cannot offer this capability or the harmonics produced by VVVF traction drives
- A remote “emergency power” control switch commands the logic in the EPS20 to start the inverter and it is then ready to power the lift traction equipment using the normal manual push button controls from within the lift car
- 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 emergency power system. We send a "ready" signal “emergency power on” to the lift control panel as soon as the EPS20 is ready for duty
- The EPS also sends a signal to the remote “emergency power” control switch panel when the EPS20 that it is "ready for duty", this signal is intended to illuminate a lamp adjacent to the key switch and can be remote connected with the summary alarm signal into a building management system
Power Systems International has also introduced a series of digitally controlled intelligent Emergency Lighting Systems (ELS D Series) that provide a centralised source of power to supply dedicated light circuits for open offices, stairways or emergency exit routes in all kinds of public premises.
To receive a quote or for further information about the EPS20 or ELS D series please contact Power Systems International Limited
Email: info@powersystemsinternational.com or Tel: 01494 871544
www.powersystemsinternational.com
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