Intelligent Motion Systems MDriveAC manual Nominal Output Torque, Speed in Full Steps per Second

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.

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.)

	140							24 VDC	99
								45 VDC
	120								85	Torque
Oz-In								75 VDC
	100								71
	80								56
in										in
	60								42
Torque										N- cm
	40								28
	20								14
	0	0	1000	2000	3000	4000	5000	6000	7000

Speed in Full Steps per Second

Figure B.1: MDrive23 Torque-Speed Curve

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 conser- vative.

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.

A-8	MDriveAC Plus Microstepping Hardware - Revision R121707
	Relevant to Firmware Version 3.0.02