…starting to fail for unknown reasons?
If it is, be sure to consider this…
Voltage power optimisation (VPO) has received increasing interest as a means of reducing electricity bills – with savings of 10 to 20% often being claimed.
VPO products balance phase voltage, filters harmonics / transients and reduces input voltage.
Great in theory but not in all practices.
Lower voltages on some motors will increase current and therefore increase costs. A number of companies are offering this type of energy saving product to the market.
Amongst these are companies who offer to simply reduce the voltage of the incoming supply to the building, thereby claiming to save energy.
This involves reducing the voltage at the supply to a value that is within the theoretical acceptable limits currently used for new electrical equipment but may be outside the design limits or initial setup of older equipment such as a lift.
Voltage Optimisation is great for constant impedance equipment such as lights, heaters, etc. but not good for constant horsepower equipment e.g. lift and pump motors.
Lift control systems and drives contain components such as relays, contactors, electromagnetically operated brakes, induction motors, DC motors and solid state drives such as Variable Frequency and Static Converters. Many of these components may have been selected to operate on a nominal 415 volt 3 phase supply to the lift.
If the supply voltage changes significantly, then some component characteristics may change to the point that the lift becomes unreliable or will not run.
In theory reducing incoming voltage by introducing Voltage Optimisation could be a major problem. This is particularly true on all lifts installed prior to 1995. In 1995 an EU initiative to allow free trade across EU boundaries was introduced, therefore motors, controllers, etc. were designed to operate over 380 – 415 volts, not 415 volts or more. (Same with domestic equipment in your home, note rated voltage is now 230 not 240).
Traction Lifts prior to the introduction of Variable Frequency drives required a high torque to start the machine to enable the load to be lifted. Torque is proportional to the square of the input voltage. Therefore; reducing the voltage will reduce the torque, the reduction is not pro rata and a small decrease in input voltage may result in a high torque loss.
Power dips may cause problems and lifts may be unable to lift full loads and motors may stall. A Variable Frequency drive fitted to an old type traction lift motor may work but is not guaranteed due to the poor efficiency of the older machines.
Variable frequency drives input current will increase in order to maintain the rated load and speed of the lift. This may overload the drive and the supply voltage supervision in the drive may shut down due to the reduced input voltage.
Hydraulic lifts (goods, goods passenger and passenger lifts) fitted with Ziehl Abegg oil submerged motors will operate over a range of 380 – 415 volts and there should be no issues even on lifts installed before 1995. Other motors such as Leroy Somer, Rexroth, Brook Crompton Parkinson and Elmo installed prior to 1995 may not provide sufficient torque to turn the pump.
If you are getting feedback on lifts not lifting full loads, fuses or overloads popping (motors stalling) or hydraulic lifts cutting out due to high oil temperature(lifts running at 380 volts actually require more current, therefore oil will get hotter). Then the cause may be attributed to the introduction of Voltage Optimisation. It is also true to say that poor maintenance, old oil on geared traction machines may also cause problems as well.
Contactors and relays may not energise correctly causing chatter and thermal overload of contacts, this will ultimately lead to lift failure.
If you discover an unusual increase in lift failures that leads you to believe the supply voltage may be suspect you should make enquiries in relation to voltage reductions systems that may have been installed. Do not assume that because voltage reduction measures have been installed there is a voltage problem. Many systems are sophisticated and will ensure the voltage is suitable and stable. If however you suspect an issue, a voltage analyser may be required to be installed on the lift supply to record the findings and enable the root cause to be identified.
Individual cases should be reviewed accordingly. However a simple solution would be to make sure the lift supply is connected to the input side of the Voltage Optimisation System and not the load side.
For more expert advice relating to your lift power problems… or any other matters, please feel free to call us on UK 01483 215 215, Intl: (0) 1483 215 215.