Replacing a DC Motor with an AC Motor

What do you exactly mean by inverter - is it for speed control?

I'm not sure how much power inverters can handle as stand alone units but these days you should be able to buy them as a set; motor combined with controller.

Not quite understanding what your are asking,

Look at this web site. ven der graaf

you can have speed control on this also.

p911

Yes it will work assuming the motors have the same basic speed and service factor ratings. The VFD (Variable Frequency Drive) unit will do all of the speed control and power handling so there should not be much for overall problems with it.

You will likely gain a few advantages as well being a good VFD unit will have some added features that most DC motor controls don't have.

My advise NO. These equipment requires very high starting torque (600% to 800%) which VFD can not give (Max.150%).

Dears,

It means if the starting torque requirement of load is less than 150% (where a DC motor is connected) then we can replace the DC motor & drive with AC motor & Inverter. OK?

Yes. I worked for some rubber companies. Study starting torque requirements at various load conditions. Do not jump into conclusion in a hurry, take several trials/ tests. Connect a power analyser or energy meter and collect Maximum demand factor of that equipment and when you are very sure that it never crosses 150%, then you can go for VFD.

Yes, but there is more to this than just the starting torque.

Look at my previous post

Yes, it can be done. I've selected a few AC motors (successfully) to replace DC motors.

Give more information on the DC motor, ie the DC motor speed. Normally DC motor has a base speed (this is the speed the 10kW is calculated from), min and max speed (the low and high speed the DC motor can operates without overheating) Normally on motor rating plate. You may also measure these speeds from the DC motor in operation or read from the DC drive.

Minimum speed is required to determine if the AC motor requires force cooling and the maximum speed to determine if the AC motor will be able to produce the required torque at that speed.

Give as much detail from your DC motor and we can select a replacement AC motor.

Yes. minimum speed is also impartent as VFD do have cogging effect at very low speeds. In this application they are already using belt drive and hence can be taken care-of.

Normally this should be possible but there are a few considerations and selection criteria to think about.

General description of application and what you are trying to achieve?

What is the main reason to change from DC to AC VFD?

What is your supply voltage?

What is the motor rating in power, speed, armature voltage, armature current?

What are the armature currents during starting, running, normal and peak?

Is the application speed or torque control?

What is the reference signal (0-10V?) and where does this come from?

What control inputs are available for operator needed or used now?

Any extra requirements?

This information will then help to determine both the suitability of correct VFD (open or closed loop, speed or torque control, or both) and motor (self cooled, force cooled, braked or with encoder feedback) for your application.

Hope this helps, I can then advise further if you wish.

I agree, should have had some of this info in the original post.

Are you looking to control the speed of the motor? If so there are DC drives, I belive AB, ABB and Eaton have these.

I don't see the need to change from DC - AC if that is all you want to do

Not a problem. Two ways to do it; inverter or d.c. motor driving a.c. generator driving a.c. motor. Done it a bunch on D.C. boats.