slow start 240v motor help

Hi

I have a 12w aquarium water pump connected to a relay timer which switches on and off about every 20 seconds.
Everytime the motor starts it shudders and makes quite a loud noise due to the quick start.
Can I add a capacitor in parallel to the motor to slow the start of the motor hence quitening the start?
If so what capacitor would you recommend?
Any other ideas?

Is it a squirrel cage, totally enclosed armature, type of motor where the armature is connected to the impeller?

hi colin55

yes the armature is connected to the impeller but as for squirrel cage im not sure as the motor is inside a sealed waterproof unit.

thanks

Is only the rotor floating in the water it is transporting?

Does the field consist of a coil of wire?

The pump is a totally submersable sealed unit with the rotor attached to a permenant magnet.

It is plugged in to a basic on/off timer switch.

In this case the armature is running in the water of the fish tank and the bearings are very sloppy. There is nothing you can do to fix the pump. It looks like it is worn out.

thanks colin for your reply but there is nothing wrong with the pump.
when the pump is turned straight on the impellor shudders under the friction of the water.
most submersible aquarium motors have a permenant magnet on a solid shaft. the magnet is attached straight to the impeller. there is no bearings, it is a very simple design.
when hooked up to an expensive timer with a slow start, there is no shudder.
the timer i have is a simple on off switch. i would like to slow the start of the pump.
is it possible to run a capacitor parallel to the pump so the pump dosnt get full power straight away?

The motor is AC and all you are powering is a coil. I don't see any way to soft-start the motor.

Hi,

aquarium pumps are normally "greased" with water. They also have a circular magnet attached to the rotary unit which rotates with plenty of play on the center rod (as a bearing). If you tilt the pump slightly (away from the motor packet windings) the magnet will not be pulled strongly towards the motor windings anymore and as a result the pump will operate quietly.

Best way to avoid any noise caused by the pump is mounting it vertically (motor axis) with the rotary unit horizontal.

This is done in all "Eheim" filter, heater and pump units.

My 10,000l aquarium was fitted with five of those units with a total exchange rate of 2,500l/hr and the silence was about the same as in a chapel.

Boncuk

hey thanks very much for your ideas Boncuk,

Are any of your pumps set up as wave makers?

This is what i am trying to do

Adze