Discussion on motor and pump speed issues
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Hello, friends of Haichuan. Today, I compared the nameplates of the pump units on site and found that the rated speed of some pumps is higher than the speed of the motors designed to drive them, while the rated speed of other pumps is lower than the speed of their corresponding motors. When the pump’s speed is lower than that of the motor, doesn’t this result in the pump operating at an excessive speed? Isn’t that also harmful to the pump itself? When the pump’s speed is higher than that of the motor, the pump cannot perform its tasks adequately, failing to meet the requirements of the process. Regarding these two options, which approach would be better? I hope my friends can give me some advice.
There must be a reason. The clues should be in the design documents; it’s recommended to check them.
Firstly, the speed of the motor remains roughly constant within the load range. Some parameters of the water pump are related to the rotational speed. Usually, the motor must be matched to the requirements of the water pump in order to meet the process needs. But it is allowed within the limits permitted by certain process requirements. For reference.
1. If the difference in rotational speed is small, there is no need to focus on the exact values. 2. For pumps, a specified rotational speed is required during design in order to determine the pump’s hydraulic and structural parameters. When determining the speed, too much consideration is not given to the rated speed specified on the nameplate of the specific motor used. Some pumps use 2-pole or 4-pole motors to achieve different hydraulic performance, provided that the designed speed of the pump is suitable for the 2-pole motor, so as to ensure that the strength of the impeller meets the required standards. 3. For the motor as well, there is a designed speed; the speed of the pump is not taken into consideration. 4. During operation, if no speed-changing device is used for coupling, the pump and the motor rotate at the same speed
I truly appreciate your valuable explanation.
When the speed of the motor is greater than that of the pump, a frequency converter can be used for adjustment
This discussion applies only to AC motors and does not cover variable-frequency motors.
Speed tolerance ±3%； If it exceeds this value, contact the manufacturer……
There’s no need to worry; it’s far from the critical speed