Is there a motor designed to be constantly overloaded?

Question

So I'm very, very new to electronics so this may be a really dumb question but here goes. Is there a motor that either a. is designed to be constantly overloaded or b. run in such a way that overloading it will not cause it to fail?

Here is the thought experiment that I would like to solve. Imagine an electric winch towing in a truck with say 1,000 lbs of force, though capable of towing in with let's say 10,000 lbs of force total. The truck is just in neutral and not providing any force in the opposite direction.

Now, imagine that the truck was put into drive and started pulling on the winch with a force of 1,100 lbs of force. In this situation the winch would be overloaded (is that the right word) and the truck would start to increase it's distance away from the winch.

Next, imagine the winch being able to sense this increased force by the truck (let's just assume that this is possible through the use of other sensors and microcontrollers) and then automatically increases it's towing force to 1,200 lbs. At this point that truck will now be pulled back in towards to winch.

Let's assume that this push and pull process continues indefinitely until the truck runs out of gas and is eventually towed all the way in. Also, let's assume that the force the truck exerts in the opposite direction NEVER exceeds the maximum 10,000 lbs total towing capability of the winch. Also, let's assume that the winch should always exert a pulling force. Meaning that we should not ever have it halt even when being overloaded by the truck.

Are there such motors out there that can operate effectively under these conditions? In my mind it seems illogical that motors would be designed for these types of purposes but I'm not sure.

Anyways, despite being very, very new to electronics here is my current thinking on this problem. From what I've read simply overloading a motor isn't the problem, but instead the overheating caused by overloading is the problem. And any time a motor is overheated beyond specifications then failure can occur. However, if a motor is overloaded while operating at only 1/10th (or some other small percentage) of it's total capabilities then the heat caused by overloading will probably not be too much for the motor to handle, right?

Like, I said this may be a really dumb question but it's one that I'm curious about and could not find the answer to anywhere else. It could be that this type of action is impossible from a physics standpoint as well, but I'm unsure. Thanks in advance for the help!!

Answer 1

Engineers use "overload" to indicate that that level is not intended for continuous use.

I mean, if a product is rated for say 900 W but a continuous overload at 1000 W is allowed, then why not simply call it 1000 W. As it can handle 1000 W continuously, the 900 W level loses its meaning.

What would make sense is 900 W continuous allowed load and an allowed overload of 1000 W for 10 seconds every 200 seconds. Note the time restriction. It indicates that you cannot have this condition continuously, only for a limited time.

Answer 2

There are "torque motors" which are designed to operate continuously stalled.

Most motors can be operated stalled provided the current is kept within appropriate limits, though they may not be designed for that operation (for example, the cooling may not be optimal because no internal fan is spinning).

An example from the distant past might be a motor that drives a reel to keep the magnetic tape taut as it emerges from the capstan drive in an old-fashioned reel-to-reel tape drive.

This is not considered 'overload' but just a mode of operation.

Answer 3

The ability of a motor to operate at low speed and high torque - in the extreme, to operate while stalled - is a matter of thermal design of the motor, providing a thermal path which will allow the motor to survive.

This is not normally done, since it produces a bulky, heavy motor which also needs careful attention to how and where it is mounted. After all, if the heat produced by the motor can't go anywhere the temperature will rise (more or less) indefinitely.

There is a class of motors which does this, and they are generally called torque motors . They are intended for high-torque, low-speed operation, and are commonly rated for continuous stall. As direct-drive motors, the load is connected directly to their shafts, and the body is commonly press-fit into a metal housing, which allows good heat transfer.

Answer 4

DC winches with brushed motors yield the highest torque and RPM depends on number of poles .

Gear reduction also transforms torque while the product with speed RPM is almost equal power on both sides with some gear losses in between.

The cooling is normally fan driven on the motor rotor if designed for high power in a small weight.

Normally if a fuse blows to protect the motor it leaves the motor to free wheel so and better electronic protection from overload is to open the electronic switches or typically a solenoid.

While shorting the motor to act as a safety brake, might be a good idea but adds extra cost.

The also have manual dial controlled brakes since an operator should be nearby.