5. Operation: Parallel and Series

5.1. Parallel

Two or more SL Series power supplies can be connected in parallel to obtain a total output current greater than that available from one power supply. The total output current is the sum of the output currents of the individual power supplies. Each power supply can be turned on or off separately.

5.1.1. Parallel - Direct

The simplest parallel connection involves attaching the positive terminals of all supplies to be paralleled to the positive point of the load and attaching the negative terminals to the negative point of the load. The output current controls of each power supply can be separately set. The output voltage control of one power supply (master) should be set to the desired output voltage; the other power supply (slave) should be set for a slightly higher output voltage. The master will act as a constant voltage source; the slave will act as a constant current source, dropping its output voltage to equal that of the master.

5.1.2. Parallel - Master-Slave

Master-slave parallel operation permits equal current sharing under all load conditions and allows complete control of output current from one master power supply. With Magna-Power’s master-slave parallel scheme, the master sends signals to control the slave unit’s gate driver, ensuring only one control loop and consistent transient response performance.

Fig. 5.1 illustrates the terminal connection for master/slave parallel operation and salient control circuitry. The control cable can be fabricated by the user or purchased as an accessory, Universal Interface Device (UID47), from the factory. These connections perform the following functions:

  • Jumper connection between ISO (Pin 16) of the slave power supplies and ISI (Pin 35) of the master power supply connects the slave power supplies current monitoring outputs to the master power supply current monitoring input. This connection allows the current of all slave power supplies to be summed along with that of the master power supply.

  • Jumper connection between CONTROL (Pin 31) of the master and slave power supplies connects the control lines between the master and slave power supplies. Command of the control line is automatically selected with the jumper connections.

  • Jumper connection between REF GND (Pin 2), VREF EXT (Pin 3), IREF EXT (Pin 22) of the slave power supplies to REF GND (Pin 2) of the master power supply enables control of the slave power supplies from the master power supply.

  • Jumper connection between POWER (Pin 8) of the master power supply to START (Pin 17) of the slave power supplies connects the power output digital control line of the master power supply to the start digital control line of the slave power supplies. This connection causes slave units to turn on when the master unit is turned on.

  • Jumper connection between STANDBY/ALM (Pin 12) of the master power supply and STOP (Pin

19) of the slave power supplies connects the STANDBY/ALM digital control line of the master power supply to the STOP digital control line of the slave power supplies. This connection causes the slaves units to turn off when the master unit is turned off or when a diagnostic condition appears. * Jumper connections between TVREF EXT (Pin 4), +10V REF (Pin 21), and TIREF EXT (Pin 23) of the slave power supplies sets the slave voltage trip and over current trip set points just beyond full scale values.

The master unit can configured for rotary, external program, or remote input. The slave power supply must be configured for external program (EXT PGM) input.

For more information on setting the slave unit to EXT PGM:

To add a second slave unit, connect the output terminals of the second slave in parallel with the other two power supplies. Furthermore, connect a second control cable between the second slave unit and the master unit, or use an additional Universal Interface Device (UID47) accessory from the factory.

_images/masterslave-parallel.svg

Fig. 5.1 Master-slave parallel DC output and JS1 37-pin external user I/O connections

5.2. Series

Two or more power supplies can be connected in series to obtain a total output voltage greater than that available from one power supply. The total output voltage is the sum of the output voltage of the individual power supplies. Each power supply can be turned on or off separately.

Caution

No plus or minus voltage should exceed the product’s output isolation specification with respect to ground.

5.2.1. Series - Direct

The simplest series connection involves attaching the positive terminal of the first supply to the negative terminal of the second supply. The load is connected between the negative terminal of the first supply and the positive terminal of the second supply. The output current controls of each power supply are operative and the current limit is equal to the lowest control setting. If any one output current control is set too low with respect to the total output current, the series power supplies will automatically crossover to constant current operation and the output voltage will drop.

5.2.2. Series - Master-Slave

Master-slave series operation permits equal voltage sharing under all load conditions and allows complete control of output voltage from one master power supply. Fig. 5.2 illustrates the terminal connection for master/slave series operation and salient control circuitry. The control cable can be fabricated by the user or purchased as an accessory, Universal Interface Device (UID47), from the factory. These connections perform the following functions:

  • Jumper connection between VO2 (Pin 5) of the master power supply and VREF EXT (Pin 3) of the slave power supplies connects the voltage monitoring voltage on the master power supply to the external voltage set point input on the slave power supplies. This makes the slave power supplies operate at the same voltage output as the master power supply.

  • Jumper connection between POWER (Pin 8) of the master power supply to START (Pin 17) of the slave power supplies connects the power output digital control line of the master power supply to the start digital control line of the slave power supplies. This connection causes slave units to turn on when the master unit is turned on.

  • Jumper connection between STANDBY/ALM (Pin 12) of the master power supply and STOP (Pin 19) of the slave power supplies connects the STANDBY/ALM digital control line of the master power supply to the STOP digital control line of the slave power supplies. This connection causes the slaves units to turn off when the master unit is turned off or when a diagnostic condition appears.

  • Jumper connections between TVREF EXT (Pin 4), +10V REF (Pin 21), IREF EXT (Pin 22), and TIREF EXT (Pin 23) of the slave power supplies sets the slave current control to maximum and sets the voltage trip and over current trip set points just beyond full scale values.

The master unit can configured for rotary, external program, or remote input. The slave power supply must be configured for external program input.

For more information on setting the slave unit to EXT PGM:

To add a second slave unit, connect the output terminals of the second slave in series with the other two power supplies. Furthermore, connect a second control cable between the second slave unit and the master unit, or use an additional Universal Interface Device (UID47) accessory from the factory.

_images/masterslave-series.svg

Fig. 5.2 Master-slave series DC output and JS1 37-pin external user I/O connection