DC motors drives and control

A DC motor is a motor powered by DC power. Sheesh, I thought that would have been obvious to anyone.

Ummmmm... go to GlobalSpec, the site that sponsors this forum, and search for "DC Motors and Drives". A link to their main page is in the upper right corner.

it could mean that to control the speed of your dc engine you need a driver (some kind of computer designed for starting different type of engines).

DC motors drives and control

Description/Notes 1/2HP, 90VDC Motor, 115VAC, 1Phase
Speed Range and Regulation: 1% over 60:1 Speed Range. Six (6) User Adjustable Calibration Pots: ACCEL, DECEL, TORQUE, IR COMP, MIN SPEED, & MAX SPEED Stopping Modes: Coast to stop with inhibit terminals (N.O.).

http://www.e-motorsonline.com/

thanks to everyone of you for the replays, however, what is the Importance of dc machine?????

Ummm... if your power source is DC, it is important to use DC drives and controls. AC equipment is not suitable to use on DC systems.

Maybe you should expaoud on your request a little more and give us the context of the question. You seem to be confused.

the dc engines have constant force and speed.

first of all, I would like to know what is the DC motor drives and controls mean.

second, I would like if someone provide me with the background on this thing something that I can understand it from A to Z.

thank you all guys

Dear Night Wolf.

DC motors, are known with good torque and with good startup characteristics comparing to the traditional AC motors. However this is not the only reason to use a DC motor.

An example, for a submarine propulsion system. The unique power source is the charged batteries beneath the water surface. No diesel engine is available due the lack of air. Then the propellers are driven with DC motors from the batteries.

One other example, Automobile electrification. All the power comes from the battery in DC form. Therefore all the motors have to be DC type. (Starter, windshield wiper, heating/cooling fans etc.).

Both type of motors (AC or DC) need drivers if their speeds are to be controlled.

Simple drivers for small DC motors are only made of resistors. Such as the heating fan speed controls in the autos.

Speed controllers for larger motors, such as submarine propeller driving were using huge resistor banks. Now I think they are all history.

But large DC motors need sophisticated drivers. Most of modern drivers are equipped with semiconductors, inverters, of which many components varying according to the manufacturers design.

Before the age, of which the semiconductor speed controllers were invented and developed for AC motors, speed control were easier by using DC motors. by varying the armature voltage and external field current.

(There were one exception, Schrage-Richter motors were AC motors, of which the speed easily controlled by turning the brushes around the armature. They can be considered as turning transormers. They were heavy and expensive motors)

Such old DC motors of over 1 Kw were controlled by Variac transformers and rectifiers from the armature side, and rheostats from the field side. Those motors had 8 terminals at the terminal box. a-b for armature, c-d for the series windings e-f for the compound windings for external excitation and g-h for the compensation windings to eliminate the sparks in the armature brushes.

However those DC motors are history now. Semiconductor drivers are easily controls the speed of any DC or AC motor precisely.

When the speed or torque control is needed for any motor, no matter it is DC or an AC motor, you need drivers.

Drivers for AC motors are in the form of frequency invertors. They rectify the mains voltage to be direct current and then form them again to be a new alternating three phase current, of which the frequency is controlled. Frequency control brings the speed control. They can change the speed of an AC motor from zero to maximum smoothly. Many of them have ramp controls to give an adjustable acceleration time to avoid inrush overloading at the startup

Voltage increases dependent with the frequency increase to maintain same amount of current to flow at any speed (for a powerful startup as well).

Kindest Regards