Remote Sense output voltage control function in MEAN WELL power supplies


One of the main tasks in the field of transmission and use of electricity is to reduce losses, which, on the one hand, create useless energy consumption, and, on the other hand, provide unnecessary heating of equipment and connecting wires. If at low power these losses may not be significant, then at medium and high power (hundreds and thousands of W) the losses can already be significant.

The presence of losses in electrical engineering is based on the fact that almost every conductive material, such as copper, has some inherent (specific) resistance. So, the resistance of the connecting wires is determined by the formula:

Lead wire resistance formula Lead wire resistance formula

As can be seen from the formula, the length and cross-sectional area of the wire directly affect the losses, and the longer the length and the smaller the cross section, the higher the resistance to electric current in the wire and, as a result, there will be more losses. Ultimately, these losses are expressed in the heating of the connecting wires, as well as in the voltage drop directly at the load connection point, which can be critical for starting or operating the final equipment. The voltage drop on the wire due to its resistance is calculated based on Ohm's law:

Voltage drop across the wire according to Ohm's law Voltage drop across the wire according to Ohm's law

Since it is not always possible and / or economically feasible to use wires of the largest possible cross section and with the lowest resistivity, it is easiest to increase the output voltage level on the power supply itself to compensate for losses to provide a given voltage level at the load. In MEAN WELL power supplies, the function of controlling the output voltage and increasing the output voltage to compensate for losses is called Remote Sense (RS).

A feature of using the function is the need to connect the RS outputs at the place where the load is connected at the output of the connecting wires via the main channel. The connection of the RS pins must be carried out with a twisted pair for noise immunity on this connection, the wire cross-section does not matter, since the current consumption for measurements is minimal. When connecting the RS wires, it is important to observe the polarity - plus to plus, minus to minus, in order to avoid failure of the power supply.

Connecting when using the Remote Sense function using the RSP-750 as an example Connecting when using the Remote Sense function using the RSP-750 as an example

The amount of voltage drop compensation is small - about 0.3-0.5V depending on the series, the adjustment of the output voltage by the power source is carried out automatically. The Remote Sense function is implemented in medium and high power case-type power supplies - a series without built-in power factor corrector (PFC) SE-1000 , powerful and functional power supplies of the PSP-600 series, low-profile power supplies with PFC of the RSP-500 , RSP-750 series , RSP-1000 , RSP-2000 , HRP-150 , HRP-300 , HRP-600 series high reliability power supplies and other series.

Also, in most MEAN WELL power supplies, a ±10% output voltage trim is built-in, which can also be used to compensate for voltage drops on the wires. In this case, when installing the power system, one-time measurements of the actual drop should be made and the output voltage should be increased by the required amount.

More detailed technical characteristics and features of MEAN WELL power supplies are presented in the Specifications on the product page. To consult or clarify information on MEAN WELL power supplies, please contact .