Simplified Resistor Sizing Based On Stopping Time - gefran BUy-1020 Manuel D'utilisation

4.5 Simplified Resistor Sizing Based on Stopping Time

1) Add Motor Inertia + Gearbox Inertia + Reflected Machine Inertia = Total System inertia
[ft lb ]
2
Reflected Machine Inertia =
2) Calculate system energy running at top speed.
[Total System Inertia] [Top rpm
3)
rmp
(System Energy) kW ⋅ sec
4) Calculate the resistor Ohms needed to dissipate the average stopping power [kW].
(DC Bus Volts)
(Ave Stopping kW * 1000 * 2)
This is the largest ohm value that can be used to stop the drive in time. Smaller Ohm
values can be used.
5)
Calculate the resistor ohms needed for the motor to reach current limit anytime during
the stop.
Motor HP * .746 = Motor kW
Current Limit kW = Motor kW * 1.5 (150% overload)
61-GB
4300000
Calculate average [kW] needed to absorb to stop, neglecting
friction and efficiencies.
time
(Stop time) sec
2
= Ω
(DC Bus Volts)
Current Limit kW * 1000
—————— Braking Unit ——————
Machine Inertia
(Gear Ratio)
2
]
2
= System Energy [kW ⋅ sec]
= Average Stopping Power [kW]
For ADV as master, at 460 Vac, DC bus
volts = 780.
2
= Ω