What can cause power surges in an elevator?
The connection of the motors used to operate elevators, hoists , lifts , etc., which are the ones that do the “hard work” in the installation, produce unnecessary intensity peaks on a daily basis.
These violent starts cause different damages, such as:
- Electrical problems due to voltage and current transients caused by direct or star-delta starting. These transients can overload the network and cause voltage variations that interfere with the operation of other electrical equipment connected to the network.
- Mechanical problems that affect the entire drive, from the motor itself to the hydraulic equipment , and can cause extreme stress on the components.
- Functional problems, such as sudden increases in pressure in the pipes .
The economic consequences can be considerable: every technical problem and every downtime costs money, both in terms of repairs and in terms of lost productivity. Soft starters are the ideal and simple solution to these problems. With this type of starter, it is possible to start and stop smoothly, reducing electrical and mechanical stress to a minimum.
The advantages and disadvantages of the three starting modes of an electric motor are summarized below: direct starting, star-delta starting, soft-starter starting.
What is direct boot
HOW DOES IT WORK?
The line voltage is applied directly to the motor terminals by contactors (electromechanical component that establishes or interrupts the flow of current). See operating curves.
DISADVANTAGES: ELECTRICAL CONSUMPTION
- A motor starting at half or full load can draw 5 to 8 times the rated current.
Example: If we perform a direct start with a 58.8 Kw motor, the installation would have to be designed to absorb 369 A, the equivalent of having more than 10 elevators installed with a power of 2.2 Kw.
- Excessive torque applied: During motor start-up, a series of sudden torque fluctuations occur as the speed increases. This excess can cause mechanical shocks and water hammer in the pump , resulting in a sudden start of the elevator.
- Massive motor overheating: Overcurrent can cause sudden voltage drops on low-capacity lines and requires appropriate sizing of contactors and fuses to avoid damage.
- Additional engine heating: causes premature engine wear.
- Cost of line sizing.
- There is no engine control.
What is the STAR-DELTA start?
HOW DOES IT WORK?
The engine is connected in two stages to reduce initial consumption by contactors. See operating curves.
DISADVANTAGES: ELECTRICAL CONSUMPTION
- A motor starting at half or full load can draw 2 to 3 times the rated current.
- Timed relays must be mounted to perform the connection change.
- Very high peak currents occur during the change from star to delta.
- High mechanical stress is produced on the engine.
- Cost of line sizing.
- There is no engine control.
Continued on What are Soft-starters?
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7 comments
Good morning Mar,
It is very good because I see that you have condensed and structured the concepts very well and adapted the ideas to our sector.
I see that you are gradually improving, I have even stayed with the suspense of seeing how the story will end on May 7th.
On the operational side, this blog will do very well.
Good job
Thank you very much!
Excellent article, with valuable information.
All the best !
Benedict
I have a recently installed GMV hydraulic lift and it starts up very abruptly, it is single-phase.
Can I put a delayed contactor?
The elevator technician says there is no solution.
He says that the speed can be lowered
If you can, please let me know as soon as possible.