How much torque can produce a DC Motor?

An AC motor can produce maximum 150% starting torque while a DC motor can produce upto 300%.

You really need to look at the manufacturer's curves for the motors. Both AC and DC motors can produce abundant torque.

If the AC motor and DC motor are operating at the same speed, then the torque produced is the same, assuming both motors are rated for the same hp output. The motors can also be about equally efficient, with high efficiency AC motors being a little easier to find, perhaps. (Some brushless DC motors can be very high efficiency -- 95% or so, whereas standard motors are apt to be 85%-90% efficient.)

AC motors typically produce very high torque at low speeds and then produce roughly constant hp at higher speeds, meaning that the torque falls off with high speed. The characteristics of a series wound DC motor are somewhat similar, while a DC shunt motor operates more or less naturally as a fixed speed motor. Compound motors are in between shunt and series in operation.

The trend in variable speed motors in industrial use has been toward AC inverter drives and away from DC drives (which were the more common variable speed motors a couple decades ago). In smaller motors, however, and where precise positioning is a concern, then DC motors are used. DC motors have long been used for traction in fork lifts, etc. although the trend has been toward AC motors in these applications.

A good book on the subject which elaborates considerably on the differences is Electric Motors and Control Techniques by Gottlieb.

Hi Guest,

This site below, may be useful.

Torque curves

D.C. Motor Torque/Speed Curve Tutorial:::Understanding Motor ...

1 : a force that produces or tends to produce rotation or torsion (an automobile .... We can express this work in terms of torque and an angular displacement. ... In other words, there is a tradeoff between how much torque a motor...lancet.mit.edu/motors/motors3.html - Cached - Similar -

Hope you find this a help.

take care.

Hi,

this depends very much on the operation mode (continuous versus short time) and on the cooling.

I saw a 10W small Faulhaber servo being operated at 1 KW for some milliseconds in a high-speed camera.

I saw a motor that used liquid copper as "windings" inside a ceramic block.

There is the established use of copper windings at -200 to - 270°C. (I had to design the flexible bearings nearby that supported the IR scanner for a survey of our Galaxy in the 10 to 100µm wavelengths.)

-200°C is resulting in a decreasing resistance of near a factor of 250 so your allowed current (and thus torque) will be up a factor of sqrt(250)=near 14.

All these examples are pure PMDC motors, magnets are stable (if designed properly) and coils are without iron, so easier to cool.

RHABE

Hi RHABE,

Nice post about the various types of Motor you have seen!

They are pretty amazing things and for the size give dependable power, so they hardly have to think about it? What would we do without Motors?

Take care.