Balance is the quiet variable behind a whole category of “intermittent” faults. A unit that behaves perfectly empty and badly loaded – or the reverse – is telling you where to look.
The two masses that shape behaviour
| Element | Function | Effect when wrong |
|---|---|---|
| Counterweight | Balances car plus roughly 40-50% of rated load | Machine works harder in one direction; brake and drive stressed; current imbalance by direction |
| Compensation ropes/chains | Offsets suspension weight as the car travels | Machine sees changing load with position; faults appear at particular floors |
| Rope/belt tension equalisation | Shares load across suspension means | One rope takes more load, wears faster, can trip a slack device |
| Car own weight (tare) | Fixed baseline | Wrong after an alteration without re-balancing |
Load-dependent symptoms and their meaning
- Fault only when fully loaded: drive torque limit, brake holding capacity, or a machine at the edge of its rating.
- Fault only when empty: the same components in the other direction, or an over-compensated system.
- Fault only going up or only going down: imbalance, brake, or a guide/rail issue that loads one side.
- Levelling error that depends on load: brake timing, or relevant levelling settings – mechanical balance does not cause levelling drift by itself.
- Different current per phase depending on direction: supply or motor, not balance.
Balance testing, done deliberately
- Measure machine current at constant speed in both directions with the same load – the comparison is what matters, not the absolute figure.
- Repeat with a known weight (for example 50% of rated load) and record both directions.
- Then repeat at rated load if the machine rating allows it.
- Compare with the original balance figure from commissioning. If balance was never recorded, record it now for the next visit.
After an alteration, re-check balance. Changing the car interior, adding a door operator, or replacing a controller can shift tare weight enough to move the machine’s duty point and create load-dependent faults that did not exist before.
Related: ride quality, ropes and belts, drives and motors.