Basic Types Of Ac Power Regulators

There are two basic types of industrial power conditioner. Basic voltage regulators are either series or parallel, depending on the position of the regulating element relative to the circuit's load resistance.

1. Parallel Regulator: While one of the simplest semiconductor regulators, the electrical power conditioner is typically the least efficient. single phase power conditioner can be used to provide a regulated output when the load is relatively constant, the voltage is low to medium, and the output current is high. Parallel regulators utilize the voltage divider principle to regulate the output voltage.

The diagram below shows the basic form of a parallel regulator. Because the regulating element is connected in parallel with the load resistor, it is called a parallel regulator. The fixed resistor R5 is connected in series with the load resistor RL and the variable resistor RrcE, forming a voltage divider in the input circuit.

A brief operational description of the basic parallel regulator will be used to explain how output voltage regulation is achieved.

All current flowing throughout the circuit flows through the series resistor RS. The magnitude of this current and the voltage drop across RS are controlled by the variable resistor Rreg. The voltage across RS is equal to the difference between the larger voltage of the DC power supply and the output voltage across the load resistor RL.

The voltage difference across Rs varies as needed, thanks to the action of resistor Rreg, to compensate for circuit variations and maintain the load's output voltage at the desired constant value.

If the input voltage to the regulator circuit decreases, the voltage across the load resistor RL and the variable resistor Rreg tends to decrease. To offset this decrease, the resistance of Rreg is increased, thereby reducing the total current flowing through Rs, and thus reducing the voltage drop across it. Therefore, by reducing the voltage difference across RS, the decrease in input voltage is compensated, and the output voltage remains constant at its nominal value. Conversely, if the input voltage is increased, the voltage across RL and Rreg tends to increase. To offset this increase, the resistance of Rreg is decreased. This results in more current flowing through RS, thus increasing the voltage across it. The increase in voltage difference compensates for the increase in input voltage, and the output voltage again remains constant at the regulated value.

The parallel regulator must be able to withstand the entire output voltage of the DC power supply; however, it does not need to withstand full current unless it needs to be adjusted from an off-state to a full-load state. Because the series buck converter Rre used with a shunt regulator has relatively high power dissipation, the regulation efficiency of such regulators may be lower than that of other types of regulators. One advantage of shunt regulators is that they provide inherent overload and short-circuit protection. The series resistor RS is located between the DC power supply and the load; therefore, a short circuit or overload will only reduce the output voltage of the regulator circuit. However, note that under no-load conditions, the shunt regulator must consume the entire output; therefore, shunt regulators are most commonly used in constant-load applications.

As can be seen from the general discussion given in the preceding paragraphs, a shunt regulator is essentially a voltage divider circuit, where the output voltage across the load remains essentially constant regardless of changes in the input voltage or load current. The control action required to change the resistance of Rre and thus produce a variable voltage drop is completely automatic. This basic principle of voltage regulation is used in the transistor shunt voltage regulator described later in this section.