[Goemon]

These are the speeds at the rated voltage.

These motors are like servo motors, where torque is constant across all rpm.

All motors produce constant torque up to the rated voltage / speed / hp. It's just the speed at which the motor hits maximum power. The specs for the 1.5hp motor on the AT site state a torque of 1.7nm (or 1.3 ft lb) which means it hits peak hp at 6000rpm. If hp does not rise past 1.5 then the torque would obviously decline from 6000rpm to 9000rpm as it switches from constant torque to constant power.

The key point I am making here is that, if you are buying these motors for a hard metal milling machine (the purpose they are sold for), you would still need a gear reduction to deliver low speed torque. I.e. there seems to be no advantage over buying a regular motor plus a vfd, and yet, they cost a good bit more.

You would get over 3 times more low speed torque with a 1.5hp 4 pole 1750rpm induction motor (with no sacrifice in higher speed torque) and they sell new for a fraction of the price. So why do people buy DC motor drives?

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These are the speeds at the rated voltage.

These motors are like servo motors, where torque is constant across all rpm.

All motors produce constant torque up to the rated voltage / speed / hp. It's just the speed at which the motor hits maximum power. The specs for the 1.5hp motor on the AT site state a torque of 1.7nm (or 1.3 ft lb) which means it hits peak hp at 6000rpm. If hp does not rise past 1.5 then the torque would obviously decline from 6000rpm to 9000rpm as it switches from constant torque to constant power.

The key point I am making here is that, if you are buying these motors for a hard metal milling machine (the purpose they are sold for), you would still need a gear reduction to deliver low speed torque. I.e. there seems to be no advantage over buying a regular motor plus a vfd, and yet, they cost a good bit more.

You would get over 3 times more low speed torque with a 1.5hp 4 pole 1750rpm induction motor (with no sacrifice in higher speed torque) and they sell new for a fraction of the price. So why do people buy DC motor drives?