Efficiencies and Power Dissipation

Abstract

As a rule, hydrostatic transmissions are more efficient than equivalent valve-operated flow controls. The choice of pump configuration can, however, significantly affect power efficiency. In Section 5.2, four basic valve control circuits were described; meter-in, meter-out, meter-in/meterout and bleed-off. In the bleed-off circuit, the pump operates as a flow source, in the other three cases the pump acts as a pressure source. We shall now examine several types of pump arrangement with special emphasis on power dissipation and efficiency. The five basic circuit arrangements are:

• (1) Fixed displacement pump at constant supply pressure.

• (2) Pressure-compensated variable displacement pump.

• (3) Fixed displacement pump with pressure match.

• (4) Variable displacement pump with power match.

• (5) Fixed displacement pump with bleed-off.

Circuits (3) and (4) can further be broken down into either fixed or variable pressure or power match.