Gearbox Selection Example – 1
Available Data About the Project
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Driven machine type: Drive type: Motor speed: Speed of driven machine nd: Torque required for driven machine Md: Daily operation time: Number of start-ups per hour: Operation time in an hour: Operation environment: G.box input speed= Motor speed: G.box output speed: |
Bucket Elevator Electric motor 1460 rpm 23 rpm 9000 N.m 24 hours Continous 60min (FD: 100%) Closed, 20°- 25°C 1460 rpm 23 rpm |
The gearbox will be connected to the motor by hydraulic coupling and to the driven machine by elastic coupling.
Gearbox types, which are selected by the technical staff, are DA3 and DK3 models.
Calculations
Power Piş required for driven machine:
Mdiş (N.m) . niş (rpm) 9000 . 23
Piş = _________________ = _________ = 21.7 kw
9550 9550
Gearbox transmission ratio: i = n1 / n2 = 1460 / 23 = 63 / 1
Operation Safety Factor F:
Motor factor fm : 1.0 for electric motors.
Driven machine factor fiş : 1.5 for elevators.
Start-up factor fdk : 1.0 for a machine operating continuously.
Daily operation time factor ft : 1.25.
Thus F = 1 . 1.5 . 1 . 1.25 = 1.875
Power gearbox should transmit: Pre = F . Piş = 1.9 . 21.7 = 41.2 kw. Nominal power Pn for selected gearbox should be greater than Pre. Pn > Pre
In power table of DA3 model gearbox, it is stated that the nominal power DA3-500 model gearbox can transmit is 55 kw for ninput = 1500, noutput = 24 rpm. Thus, DA3-500 model gearbox is suitable for this project.
Thermal power of DA3-500 model gearbox is Pt = 75 kw Since Pt > Pre, DA3-500 model gearbox can transmit power Pre without cooling.
In the power table for DK3 model, nominal power of DK3-400 model gearbox is stated as 55 kw under same operating conditions. Since Pn > Pre, DK3-400 can also be used for this project.
Gearbox Selection Example – 2
Available Data About the Project
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Driven machine type: Drive type: Motor speed: Speed of driven machine niş: Torque required for driven machine Td: Daily operation time: Number of start-ups per hour: Operation time in an hour: Operation environment: Gearbox and motor connection: Pulley ratio: Gearbox input speed Gearbox output speed
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Belt Conveyor Electric motor 1450 rpm 60 rpm 1800 N.m 10 hours At most 5 50min (FD: 80%) Open, 25°- 30°C V-belt pulley 1.5 / 1 1450 / 1.5 =960 rpm 60 rpm |
Gearbox is mounted on conveyor shaft.
DG2 model shaft mounted gearbox is suitable for this project.
Calculations
Power Piş required for driven machine:
Mdiş (N.m) . niş (rpm) 1800 . 60
Piş = _________________ = _________ = 11.3 kw
9550 9550
Gearbox transmission ratio: i = n1 / n2 = 960 / 60 = 16 / 1
Operation Safety Factor F
Operation safety factor can be taken from the table on page 17 as 1.5, for a conveyor which is a machine driven by electric motor, operating 10 hours daily, with medium shock loading.
Power gearbox should transmit: Pre = F . Piş = 1.5 . 11.3 = 17 kw.
Nominal power for selected gearbox should be greater than power Pre. Pn > Pre.
In power table of DG2 model gearbox, it is stated that for ninput = 1000, noutput = 63 rpm, the nominal power of DG2-250 model gearbox can transmit is 20 kw. DG2-250 model gearbox is suitable for this project.
Thermal power of DG2-250 model gearbox is Pt = 40 kw (from thermal power table.)
Since Pt > Pre, DG2-250 model gearbox can transmit power Pre without cooling.
Gearbox Selection Example – 3
Available Data About the Project
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Driven machine type: Motor power: Motor speed: Speed of driven machine niş: Torque required for driven machine Mdiş: Daily operation time: Number of start-ups per hour: Operation time in an hour: Operation environment: Chain sprocket ratio: Gearbox input speed = Motor speed: Gearbox output speed: |
Drying Mills 15 kw 1460 rpm 24 rpm 4650 N.m 10 hours At most 5 60 min (FD: 100%) Open, 25°- 30°C 2.5 / 1 1460 rpm 24 x 2.5 = 60 rpm |
Motor is directly connected to gearbox. Gearbox is connected to drying mill with chain sprocket.
DMA3 model, heavy industry type motor gear is suitable for this project .
Calculations
Power Piş required for driven machine:
Mdiş (N.m) . niş (rpm) 4650 . 24
Piş = _________________ = _________ = 11.7 kw
9550 9550
Operation Safety Factor F
Operation safety factor can be taken from the table on page 17 as 1.5, for a drying mill which is a machine driven with electric motor, operating 10 hours daily, with medium shock loading.
Since a motor with 15 kw power is connected to gearbox, safety factor in motor selection is Pm / Pd = 15 / 11.7 = 1.3
In the power and selection table of DMA3 model gearbox , it is shown that for 15 kw power and 60 rpm gearbox output speed, DMA3-120 model gearbox with 1.8 service factor should be selected. The nominal power DMA3-120 model gearbox is
Pn = 15 . 1.8 = 27 kw.
Actual safety factor based on power required for driven machine Piş is Pn / Piş = 27 / 11.7 = 2.3.
Motor gear is selected with a safety factor greater than necessary.
