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How Does a Variable Frequency Drive Convert AC to DC
by Lin Lin SEO
How Does a Variable Frequency Drive Convert AC to DC
Explanation of AC vs. DC
Electricity can be thought of as the movement of electrons. As such, it can usually be described as being either AC (alternating current) or DC (direct current). With direct current, the electrons only move in one direction (forward) so the electrical current is always going in the same direction. Alternating current involves directions moving in two directions--backwards and forwards--which causes the electrical current to change directions. Alternating current also involves a constantly changing electrical current that can be described as a wave. This means that the direction of the current and amplitude change
Variable Frequency Drives
Variable frequency drives are systems that are able to control the speed at which an AC electrical motor rotates. They're able to do this by changing the frequency of the electrical current that's supplied to the motor (the frequency is a measure of how quickly the alternating current completes one full cycle of its wave motion). In order to do this, the variable frequency drive must first convert the incoming AC power to DC, which it does using a rectifier bridge. A rectifier bridge is made up of at least four subunits called diodes, which keep the current always moving in one direction (forward). When the current tries to go in reverse, the diodes reroute it so that it's still moving forward, into the variable frequency drive.
Other Aspects of Variable Frequency Drives
Because the motors that are attached to variable frequency drives run on AC power, the drive must be able to convert the already converted DC power back to AC power. It uses a special kind of circuit,Dreambox dm800 called an inverter switching circuit, to switch the electrical current back to a modified alternating wave form. This kind of circuit is usually able to be controlled externally by changing the settings on the control panel, which will then change the frequency at which the inverter switching circuit generates the waves. This allows for control over the speed of the attached electrical motor.
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