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A-8
Nominal Output Torque
Calculate the nominal output torque using the torque values from the MDrive's Speed/Torque Tables.
Nominal output torque (T
) is the actual torque generated at the Planetary Gearbox output shaft which
N
includes reduction ratio (i), gear efficiency (η) and the safety factor (s
ratio (i) is determined, the nominal output torque (T
× i × η ÷ s
T
= T
N
M
Motor torque × reduction ratio × gear efficiency ÷ safety factor = nominal output torque.
For gear efficiency (η) refer to the Mechanical Specifications for the 7:1 Planetary Gearbox designed for
your MDrive.
For motor torque (T
MDrive you have, the torque range will vary. The torque will fall between the high voltage line and the low
voltage line at the indicated speed for the MDrive. (See the example Speed/Torque Table below.)
140
120
100
80
60
40
20
0
0
The Speed/Torque Table above is for an MDrive23 Double Length Motor. This MDrive will produce a
torque range of 51 to 95 oz-in in the full voltage range at the speed of 2000 Full Steps/Second (600 RPM).
Please note that this is not the usable torque range. The torque output to the Planetary Gearbox must
include a safety factor (s
) to allow for any voltage and current deviations supplied to the MDrive.
f
The motor torque must include a safety factor (s
nominal output torque calculation. A 0.5 safety factor is aggressive while a 0.7 safety factor is more conser-
vative.
Example:
The available motor torque (T
NOTE: You may specify a torque less than but not greater than the motor torque range.
For this example the motor torque (T
A 6.75:1 reduction ratio (i) has been determined.
Gear efficiency (η) = 80% from the appropriate table for the Planetary Gearbox which is used
with an MDrive23.
Nominal output torque would be:
= 35) × reduction ratio (i = 6.75) × gear efficiency (η = 0.8) ÷ safety factor (s
Motor torque (T
M
= 0.5 or 0.7)
35 × 6.75 = 236.25 × 0.8 = 189 ÷ 0.5 = 378 oz-in nominal output torque (T
35 × 6.75 = 236.25 × 0.8 = 189 ÷ 0.7 = 270 oz-in nominal output torque (T
With the safety factor (s
) and gear efficiency (η) included in the calculation, the nominal output torque
f
(T
) may be greater than the user requirement.
N
) can be calculated as follows:
N
or:
f
) see the appropriate MDrive Speed/Torque Table. Dependent on which
M
1000
2000
3000
4000
Speed in Full Steps per Second
Figure B.1: MDrive23 Torque-Speed Curve
) ranging from 0.5 to 0.7. This must be factored into the
f
) is 51 to 95 oz-in.
M
) will be 35 oz-in.
M
or
MDriveAC Plus Microstepping Hardware - Revision R031808
) for the MDrive. Once the reduction
f
24 VDC
99
45 VDC
85
75 VDC
71
56
42
28
14
5000
6000
7000
)
N
)
N
Relevant to Firmware Version 3.0.02
f
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