Energy Savings are available for Hydraulic Powers Packs.
Reducing the motor speed at off load times will offer significant energy savings. Savings are available by reducing the volume of oil flowing against the by-pass valves, when movement of the load cylinders is not called up by the control system. Reducing the flow while the by-pass pressure is maintained, will provide savings roughly in proportion to the reduction in speed.
Option 1 Simple Open Loop Control Scheme: -
The requirements are:
- Install a suitable Inverter Drive in the power circuit of the existing motor.
- Set the Inverter Drive for two speed operation from digital inputs.
- Set high speed at its normal operating speed and low speed to a value to maintain minimum oil flow at full pressure against the by-pass valves.
- Reduce the acceleration and deceleration ramp times.
- Arrange Volt free contacts from the valves controlling the movement cylinders to call up high speed when cylinder movement is required and low speed when all movement valves are closed.
Install an IP20 protected Inverter Drive into an existing or new panel, or install an IP66 Inverter Drive independently mounted nearby.
The drive will need to be capable of a rapid speed change from low speed to normal operating speed. The minimum speed should not be set below 50% unless the load Current is significantly below is continuous rating or a motor force cooling fan is fitted. The deceleration ramp setting is not required to be so short and could be extended to support repeated cylinder movements, then reducing the motor speed over a few seconds when the load cylinders are idle.
Option 2 Closed Loop Control Scheme: -
The requirements for a large Hydraulic Power Pack are:
- Install a differential pressure sensor close to the machine cylinders.
- Install an Inverter Drive in the power circuit of the existing motor having a PI or PID feature.
- Arrange the actual pressure signal as feedback for the closed loop control system in the Inverter Drive.
- Set a value of pressure above the working pressure of the cylinders and below the by-pass pressure.
The PI or PID function of the drive set in closed loop control would maintain the working pressure at the cylinders. The motor speed and hence the volume of oil required would be automatically adjusted to maintain the pressure set.
The drive and its PI/PID setting will need to be capable of a rapid speed changes to accommodate changes in oil flow without momentary loss of pressure. The minimum speed limit from the PI/PID should not be set below 50%, unless the load Current is significantly below is continuous rating or a motor force cooling fan is fitted.
If there is a cooling fan on the power pack, this could be arranged in closed loop control with feedback from a temperature sensor located in the oil pipework. ‘Fan Law’ states kW load is proportional to the ‘Cube’ of speed. This means a 20% reduction in fan speed will provide a 50% reduction in kW load.
Increased maintenance periods would be an additional benefit of adding speed control.
For more information contact us.