Basic Operation

Power Converters & Transfer Relays

Progressive Dynamics is discontinuing support for our older products listed below. We are providing customers with owners manuals and troubleshooting information for the discontinued models.  Unfortunately we will no longer be able to provide support for these models.


Power Converters...How They Operate

Power Converters consist of the following components

  1. Transformer – Reduces the 120 VAC from the Shore Power Cord down to approximately 13.8 Volts AC (Alternating Current) at its secondary output.
  2. Diode Rectifier – Converts the 13.8 Volts AC from the Transformer secondary output to approximately 13.8 Volts DC (Direct Current)
  3. Relay – Automatically disconnects the RV Battery from the 12-volt RV circuits and then connects the 13.8-volt power to the RV 12-volt circuits when Shore Power is connected to the RV.
  4. Battery Charger Circuit Board – Senses the battery voltage and then provides a signal to the SCR (Silicon Controlled Rectifier) to turn it ”ON”, which in turn supplies charging current to the RV Battery. The charger board is equipped with an LED (Light Emitting Diode) that indicates the charging status as follows. (LED optional on some units)
    1. Light “ON” all of the time – The battery is being charged.
    2. Rapidly Flashing Light – The battery is approximately 90% charged.
    3. Very Slow Flashing Light – When the light blinks approximately every 5-10 seconds, the battery is fully charged.
  5. SCR (Silicon Controlled Rectifier) – This is basically an electronic switch that is controlled by the circuit board. It is turned “ON” when the battery needs charging current and is turned “OFF”, when the circuit board senses the battery is charged.
  6. Current Limiting Resistor – This resistor limits the amount of charging current that can be delivered to the battery.

In Figure 1 shown above no AC power is connected to the RV. The RV battery is supplying 12-volt power (Red Arrows ) to the RV branch circuits through the N.C. (Normally Closed) contacts of the relay. See figure 2 below for operation when AC power is applied. The Isolated Circuits for the Radio, TV or Stereo are connected directly to the battery positive terminal. (Green Arrows).

When AC power is applied, the Transformer reduces the 120 VAC down to 13.8 VAC (Alternating Current). It is then fed through the Diode Rectifiers, which convert this AC Voltage to 13.8 VDC. This DC power is also fed to the Relay Coil, which in turn pulls down the center arm of the Relay so that it makes contact with the lower N.O. (Normally Open) contacts. Now the converter feeds DC Power to the branch circuits (red arrows). This action also disconnects the RV battery from the branch circuits and places it on charge (blue arrows). Note that the DC power for the Isolated Circuits is always coming directly from the battery or the charging circuit when 120 VAC power is applied to the RV (green arrows).

NOTE: All models operate in this same manner.

Transfer Relays...How They Operate