Wiring of a workshop planer

[Thermo]

Ive put this in electrics as it is specifically an electrical question.

i have a large old dewalt planer thicknesser type dw1150, which is a 240volt model. The incoming wiring goes through an industrial type on off switch box, with a large red stop button. from there it goes to a small box that has a condensor in it. When i bought it the old boy said it needed a new condensor.

When i opened it up to replace the condensor (which ive done) i found there were some wires that were unconnected in the switch gear housing. Having managed to get some photos from someone else with a working one, ive wired it all up as it should be. When i power it up i get a hum from but nothing else. (also stops humming if i press the off switch!) the motor turns freely by hand.

Based on the limited info ive posted so far anyone got any ideas?

secondly, what is the function of a condensor?


Ill see what other info i can get from the machine if needed.

 

[holmslaw]

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[TicklyT]

Many single phase AC motors are not inherently self-starting. The rotor would just vibrate in the alternating magnetic field around it, not knowing wether to spin clockwise or anticlockwise.
In three phase motors the magnetic field appears to rotate, rather than alternate, so the rotor just follows it.

Adding a condensor to a circuit shifts the relationship between maximum current and maximum voltage, so a condenser is used, along with a second field winding in the motor to generate a second phase. With two phases, the field appears to rotate instead of just alternating. This kicks the rotor around far enough to start it spinning. Once spinning, an alternating field is usually sufficient to power it, so the second winding is often disconnected by a centrifugal switch inside the motor case.

The direction of rotation of the motor is usually determined by the connections to the second field winding. Reversing them reverses the direction of rotation.

If the centrifugal switch or condensor has failed open circuit, or is connected incorrectly, the start winding will not function, so the motor will not spin.

Same will happen if the main field winding is open circuit.

 

[Thermo]

that explains it.
i by passed the switch and it works fine. having looked at the switch wiring connections, they all appear to be rusty and to have seen better days, so now i know it works, ill order a replacement.

many thanks

 

[Thermo]

ok next question. Im looking to replace the switching unit, but a bit confused with what i need.

i assume im looking at something like this:-

http://www.toolstation.com/shop/Ele...ories/DOL+Starter+240V+3KW/d190/sd3080/p95364

am i right in thinking it comes with the gubbins inside and this will be all i need to replce it?

the original is here and it may as well be written in greek!

Untitled

• Thermo
• 9 May 2010
• 1

Untitled

• Thermo
• 9 May 2010
• 1

 

[viewer]

No volts switch?

 

[ricicle]

That is just a straightforward DOL starter with no overload. There are two aux. contacts, one for start and one for stop. The orientation will need to be maintained for the pushbuttons to reach the contacts.
How do you know that this one has failed ?

 

[holmslaw]

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