Transcript - Mitsubishi Electric Factory Automation

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Industrial Automation
How to calculate brake duty?
i=1:4
Inverter
FR-A740-7.5k
M
Gearbox
Pully
Lowering speed
3m/s
Lifting distance = 30 m
Period of cycle = 120sec.
Load
300 kg
Mitsubishi Electric – Inverter basics
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Industrial Automation
Needed technical data from the application
Load
Lifting distance
Lowering speed
Efficiency
Period of cycle
Mitsubishi Electric – Inverter basics
ML = 300 kg
h = 30 m
v =3m/s
h Mechanism = 98%
h Gearbox
h Motor
t total
= 95%
= 92%
= 10 min.
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Industrial Automation
Calculation of the Potential Energy
W pot. = ML
X
g
x
h = 300kg
X
9,81m/s²
x 30m
ML = 300 kg ( Load )
g = 9,81 m / s² ( gravity )
h = 30 m ( lifting distance )
Wpot.
kg m 2
 88290
s2
Ws  J 
The potential energy which is stored in the raised load. Is now given back to
the brake resistors in time t Brake .
Mitsubishi Electric – Inverter basics
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Industrial Automation
Brake power if lowering speed is slow
Calculation of Braking Time :
t Brake 
h
30m

 10 s
v
3m
s
Within 10 s, the entire potential energy will be feed back into the brake resistors.
Calculation of the Brake power :
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PBrake 
W pot.
PBrake 
88290Ws
* 0,95 * 0,98 * 0,92  7,562 KW
10s
t Brake
* h Gearbox *h Mechanism * h Motor
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Industrial Automation
Brake power if lowering speed is high
Calculation of Braking Time : t Brake 
h
30m

 0,5s
v
60 m
s
Within 0,5 s, the entire potential energy will be feed back into the brake resistors.
Calculation of the Brake power :
PBrake 
W pot.
t Brake
PBrake 
Mitsubishi Electric – Inverter basics
* h Gearbox *h Mechanism * h Motor
88290Ws
* 0,95 * 0,98 * 0,92  151KW
0,5s
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Industrial Automation
Duty cycle
Every option which is working with a brake resistor has a
duty cycle. With this value you can calculate the shortest
time to the next allowed brake duty.
Duty cycle
Mitsubishi Electric – Inverter basics
Ed 
t1
t2
[%]
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Industrial Automation
Ed in case of A700 and external
brake Resistor
Jumper PX->PR
only PR
100% torque,
10% ED
100% torque,
6% ED
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Industrial Automation
In case of slow lowering speed Ed fits
10s
Period of cycle = 120sec.
Duty cycle
Mitsubishi Electric – Inverter basics
Ed 
t1 10s

 8,33%
t 2 120s
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Industrial Automation
But brake power is to high!
Braking capability of ABRH series
PBrake 
Mitsubishi Electric – Inverter basics
88290Ws
* 0,95 * 0,98 * 0,92  7,562 KW
10s