confused about stepper motor torque

[cubdh23]

Ok, i have been trying to get a feel for how powerful a stepper motor is by reading it's specs but i still dont get it.
For example I have a Slo-Syn stepping motor RUN 220 oz.in 72 RPM
120V 0.33 AMPs.
I know that the 220 oz.in tells the torgue but I have seen online of stepper motors that read RUN 300 oz.in but only 2.4 Volts 3 amps.
How can a motor running at 7 Watts from the same company be more powerful than a motor rated at 40 Watts?
Can someone please explain?
thanks.

 

[Styx]

Ok, i have been trying to get a feel for how powerful a stepper motor is by reading it's specs but i still dont get it.
For example I have a Slo-Syn stepping motor RUN 220 oz.in 72 RPM
120V 0.33 AMPs.
I know that the 220 oz.in tells the torgue but I have seen online of stepper motors that read RUN 300 oz.in but only 2.4 Volts 3 amps.
How can a motor running at 7 Watts from the same company be more powerful than a motor rated at 40 Watts?
Can someone please explain?
thanks.

I hate awkward units Torque is Newton-meters, oz.in is just energy (but then again so is Nm, but Nm is more convineient)

Machine 1)
Torque = 220 oz.in = 1.5535414 newton meter
speed = 72 RPM
Voltage = 120V
Amperage = 0.33A

Machine 2)
Torque = 300 oz.in = 2.1184655 newton meter
speed = Not stated
Voltage = 2.4V
Amperage = 3A


Power is such an abstract term.
Just because a machine is rated at 120V and 0.33A does not mean that it will take that. Yes you may supply it with 120V but it will only draw as much amperage as it needs to meet the load.

An indication of a machines power is done by the machanical power equation:

P = Tw
P = power in watts
T = torque in Nm
w = rotor velocity in rad/s

thus how can you say one machine is more "powerful" than another if speed (a critical component) is not stated.

IF a machine delivers 1000Nm at 1rpm it is only outputting 100W of useful power (forget about copper/iron losses needed to get that torque)
Equally if a machine was rotating at 1000rpm against 1Nm it is also outputting 100W.

Not very powerful

IF it was 1000rpm against 1000Nm then that is a decent amount of power - 100kW !!!