Intelligent Motion Systems MDrive34Plus manual Nominal Output Torque

Nominal Output Torque

Calculate the nominal output torque using the torque values from the MDrive’s Speed/Torque Tables.

Nominal output torque (TN) is the actual torque generated at the Planetary Gearbox output shaft which includes reduction ratio (i), gear efficiency (η) and the safety factor (sf) for the MDrive. Once the reduction ratio (i) is determined, the nominal output torque (TN) can be calculated as follows:

TN = TM ⋅ i ⋅ η ⎟ sf or:

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.

	1000
	900
- In	800
	700
Oz
	600
in
	500
Torque
	400
	300
	200
	100
	0 0

							706
							635	Torque
					24 VDC		465
					45 VDC
							494
					75 VDC
							423	in N
							353
								-
							282	cm
							211
							140
							71
1000	2000	3000	4000	5000	6000	7000
(300)	(600)	(900)	(1200)	(1500)	(1800)	(2100)

Speed in Full Steps per Second (RPM)

Figure B.1: MDrive34 Torque-Speed Curve

For motor torque (TM) see the appropriate MDrive Speed/Torque Table. Dependent on which 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.)

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 (sf) to allow for any voltage and current deviations supplied to the MDrive.

The motor torque must include a safety factor (sf) ranging from 0.5 to 0.7. This must be factored into the nominal output torque calculation. A 0.5 safety factor is aggressive while a 0.7 safety factor is more conserva- tive.

Example:

The available motor torque (TM) is 51 to 95 oz-in.

NOTE: You may specify a torque less than but not greater than the motor torque range.

For this example the motor torque (TM) will be 35 oz-in. 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:

Motor torque (TM = 35) ⋅ reduction ratio (i = 6.75) ⋅ gear efficiency (η = 0.8) ⎟ safety factor (sf = 0.5 or 0.7)

35 ⋅ 6.75 = 236.25 ⋅ 0.8 = 189 ⎟ 0.5 = 378 oz-in nominal output torque (TN) or

35 ⋅ 6.75 = 236.25 ⋅ 0.8 = 189 ⎟ 0.7 = 270 oz-in nominal output torque (TN)

With the safety factor (sf) and gear efficiency (η) included in the calculation, the nominal output torque (TN) may be greater than the user requirement.

Appendices A-7