Energy Efficient Drive Selection

Many pump systems are designed without variable speed drives because only one duty point is planned. As explained under Motor Selection, most electric motors are oversized and pump flow is regulated by a valve. This increases friction to achieve the correct flow rate, so energy is wasted.

CP pumps with variable speed drives

The relationship between a pump’s speed and its energy requirement is known as the cube law because the need for power increases with the cube of the speed. This means that a small increase in pump speed requires a lot more power, but also that a modest speed reduction can yield significant energy savings. Using a variable speed drive, a pump running at half speed consumes only one-eighth of the energy compared to one running at full speed.

Frequency inverters are very cost-effective and often deliver a payback in a matter of months on energy savings alone. In addition, by matching the speed to the needs of the process, users often find they get better product quality and reduce maintenance costs. While some companies, not least small and medium-sized enterprises, are reluctant to take the financial risk of replacing drives, they can often benefit from state, local and utility energy efficiency incentives that are offered in many countries to help lessen the initial financial burden.

Variable speed drives not only cut your energy costs but also improve process control, increase production capacity, reduce maintenance costs and require less reactive power. Other benefits of these drives include:

• Smooth starting reduces maintenance
• Infinitely variable speed control provides accurate process control
• Full motor protection prevents many cable and motor faults
• Soft starting and stopping minimises mechanical wear in the process
• Wide range of speed, torque and power gives accurate speed control, resulting in process optimisation and better product quality
• Improved power factor helps maintain motor efficiency at reduced load
• EMC protection prevents interference with other sensitive equipment
• Productivity increases as motor speed is correctly matched to load requirements

Variable speed drives reduce energy wastage in all phases of operation. Changing production volumes by mechanical means is very inefficient. With variable speed drives, this can be achieved by adjusting the motor speed. Particularly in pump applications, that saves a lot of money because the shaft power is proportional to the flow rate. This is why CP partners with various drive manufacturers to offer you a wide choice of drives.

CP partners offer a range of variable speed drives from 0.05 kW to 100 kW

• Low voltage variable speed drives

Learn more about how CP can help you save energy.