Can a 37KW pump be used with a 30KW inverter?
Thread Content
The process requires 80 m3/h and a head of 20 meters. The customer has a pump they would like to use. But it has a flow rate of 160 m3/h, a head of about 40 meters, and a power output of 37 KW. Since the design capacity will not exceed 100 m3/h, can a 30 KW frequency converter be used to reduce the speed in order to achieve a flow rate of 100 m3/h along with a lower head pressure?
Without knowing the specific conditions on site, it is not recommended to use a 30KW inverter. 1. If the frequency converter is added only for process requirements, it is not necessary. 2. To make use of existing equipment, the shaft power can be reduced by cutting the impeller; however, the power level after cutting might still be higher than what is required by the process. It’s not clear whether the process requirements are very strict. 3. Choose a frequency converter of 37 KW that matches the motor, and then reduce the frequency
This question can probably be answered by electrical technicians as well
With a voltage of 440V and 60Hz, can an inverter enable the pump to operate at below 30Hz for an extended period of time?
I have no experience with 440V, but based on my own experience, it is not advisable to keep the frequency of an inverter constant for an extended period; its advantages lie in energy savings and adjustability, so it should not be used in that way.
The process requires frequency conversion. However, the pump’s flow rate and head are almost twice the designed values, so it is necessary to operate at a lower frequency. It is estimated that the speed needs to be reduced by half.
There is a pump performance curve, and variable frequency control allows for greater accuracy
The head ratio is equal to the square of the speed ratio, which in turn is equal to the square of the frequency ratio. When the height is reduced from 40 meters to 20 meters, the frequency is 35 Hz; at this point, the flow rate is 160×0.7=100 cubic meters. The shaft power is approximately 11–15 kilowatts. It’s no problem to use 30 kilowatts to drive a 37 kilowatt motor. But the problem is that once your frequency drops to 35 Hz, the pump’s efficiency will decrease by at least 20%. With such low efficiency, it’s more cost-effective to replace it with a new pump. If it is only to be used temporarily, first cut the diameter of the impeller by 20% before using variable frequency drive; this will increase the frequency and enable better heat dissipation. The shaft power is already low, so the actual power of the motor is also low; it can be used. Personally, I still recommend replacing it with a new pump; the electricity savings over a year would be enough to cover the cost of four new pumps.
Select a frequency converter of 37KW that is suitable for the motor; in most cases, a 45KW frequency converter is chosen