Energy can flow back from the load.
A motor can generate electrical energy when electromagnetic torque opposes its rotation. This can happen during deceleration or when gravity drives an unbalanced load.
In a traction lift, load and direction matter. A heavily loaded car descending or a lightly loaded car ascending can produce generating conditions, depending on balance and losses.
The electrical system needs an energy path.
- Motor generatesMechanical energy enters the electrical system.
- DC link receivesReturned energy can raise DC-link voltage.
- Energy is managedA resistor dissipates it or suitable equipment returns it to the supply.
A braking resistor converts energy into heat.
A braking chopper can connect a suitable resistor to the DC link as required. The resistor dissipates electrical energy as heat rather than returning it to the supply.
Its duty involves both power and energy over time. A resistor’s resistance alone does not describe its ability to absorb repeated or prolonged braking.
Energy and time determine average power.
That is 2,000 W average during the interval. Short peaks and repeated cycles can impose different thermal demands.
This is an energy example, not a resistor-selection calculation. Actual requirements include the drive limits and duty cycle.
Returning energy needs compatible equipment.
A regenerative front end or suitable regeneration unit can return energy to the supply. An ordinary diode input bridge cannot simply pass power backwards to the mains.
Electrical braking controls energy flow while moving. It does not remove the need for the lift’s mechanical holding brake and other safety provisions.
A closer look
Generating operation is not limited to slowing down. A gravity-driven load can return energy during steady-speed travel, so braking duty cannot always be estimated from stopping events alone.
Check your understanding
Does every VFD return braking energy to the electricity supply?
Reveal the explanation
No. Some installations dissipate it in a resistor. Returning it to the supply requires a suitable regenerative power path.