Can the "slip" of a fixed frequency induction motor be used to estimate power?

[e100]

I have a single phase induction motor and centrifugal pump that pumps water through a filter that gets clogged over time.
As the flow decreases, does the motor speed increase and get closer to the line frequency? In other words does the rotor slip decrease because it is moving less water and therefore doing less work?
In theory it sounds like it should but I don't know in practice and I don't have an easy way of clogging the filter to do the experiment.
If this is correct it would be an easy way of measuring the flow rate without installing flow meters.

Mike

[amiq]

Hello Mike, yes the slip can be used to estimate the output power.  But you'd have to test your pump to see how it behaves when blockages are introduced.

[Zero999]

What sort of pump is it?

[TimFox]

In an induction motor, there is a curve for rpm vs. torque, where the slip (rpm less than synchronous frequency) goes to zero at zero torque (although there is always some torque required for the bearing).  You could use the manufacturer's data curve to estimate the torque for a measured rotational frequency.

[Delta]

If it's a positive displacement pump, the mechanical load on the motor, and therefore the slip, will increase as the filter clogs, due to the increase in backpressure.

If it's a centrifugal pump, the load (and slip) will decrease as the increased backpressure results in a reduction in flow.  (I think...)

[Seekonk]

I think I would look a phase angle between voltage and current.

[G7PSK]

If the filter is on the output side of the pump the load on the motor increases as the pressure rises, dose not matter whether that is due to the head height or restriction on flow. If the filter is on the input side less fluid in the pump will reduce the load but either way with an induction motor the speed will not vary very much. It would be better to put a pressure sensor in the filter.