Elevator voltage dip and frequency dip

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shortcircuit1

Senior Member
Location
USA
Hello,

I am sizing a generator with one elevator on emergency.Its 25HP,3phase,208v.When you select the load as elevator in sizing software if defaults to a voltage dip of 15% and frequency dip of 5 Hz. I tried to contact with the elevator manufacturer to see whats the voltage and frequency dip that their controller can withstand when the generator kicks in but they dont seem to have any idea what i m talking about. This is a KONE MRL(Machine room less) elevator.

Any thoughts or has anyone sized with the elevator on generator?

Thanks,
shortcircuit.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
180731-0857 EDT

Shortcircuit1:

I can't answer your question.

Internal combustion engines are peak power limited. If you exceed that power, then engine stalls. Said engine can possibly run continuously at its peak capability. Thus, engine needs to be big enough to handle motor starting power.

An electrical device (resistor, transformer, motor, generator) may be able to be greatly overloaded, run many times its rated continuous value, for a short time.

You have two things to consider. What is peak load power when elevator motor starts? Your engine will need a capability somewhat above this.

Your voltage dip, and frequency drop will be determined by the equivalent source impedance of the engine and generator, and the motor load on that source impedance.

.
 

shortcircuit1

Senior Member
Location
USA
180731-0857 EDT

Shortcircuit1:

I can't answer your question.

Internal combustion engines are peak power limited. If you exceed that power, then engine stalls. Said engine can possibly run continuously at its peak capability. Thus, engine needs to be big enough to handle motor starting power.

An electrical device (resistor, transformer, motor, generator) may be able to be greatly overloaded, run many times its rated continuous value, for a short time.

You have two things to consider. What is peak load power when elevator motor starts? Your engine will need a capability somewhat above this.

Your voltage dip, and frequency drop will be determined by the equivalent source impedance of the engine and generator, and the motor load on that source impedance.

.

I dont have the information that you are asking for.But i am curious to see how other people size their generators especially with so much stringent restrictions on elevator voltage and frequency dip
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
180802-1106 EDT

shortcircuit1:

Assume your 25 HP motor is 30 HP and that starting current is 3 times full load current, then guess at 100 HP for the generator drive engine. There is some mechanical inertia in the generator system. Is this enough to carry thru motor startup? My guess is not.

You need to find out starting current and duration. Then contact generator manufacture and see what they suggest to meet your specifications.

.
 

topgone

Senior Member
How are they starting their elevator motor? Auto-transformer start? VFD? or DOL?
If you have the transient reactance of your genset, you can compute for the voltage dip when starting the elevator motor at its starting method. Most controllers can withstand a 20% voltage dip.
 
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