High/Low Speed 3 Phase Fan Contror???

[gareth020]

Hi

I've been asked to move 2 x 3 phase fan control boxes with high and low speed start buttons, stop buttons and LED indicator lamps. They control 2 roof fans. Inside one of the boxes the coil has gone on one of the contactors and needs replacing, but to be honest both boxes are quite old now and the cabelling has not been installed to a good standard. So i was going to suggest replacing the whole unit, but don't want to attempt this until i understand the theory and how it all works. Could anyone suggest where i could get a wiring diagram to study or point me in the right direction on how the control circuit works??? I have searched the forum etc but not found anything yet.

Much appreciated guys

 

[Bidder]

Do you mean star and delta. If it is then this link may help you. Scroll down to 4. Contactors controlling a STAR-DELTA motor and
[h=3]7. Different types of AC Motors[/h]
Good luck

http://claydons.org/public-html/elec/contactor.htm

 

[gareth020]

Thanx, It is set up like that, expect no timer, you manually press the low speed start or high speed start. How does that work?

 

[silva.foxx]

Have a look at this ebook >> http://www.moeller.net/binary/schabu/wiring_man_en.pdf << in the section All About Motors. In there you'll find excellent examples of what you'll be wanting under Multi-speed control, etc...

 

[Knobhead]

As Silva has said have a look through the e-book. There's only 700+ pages

The starters are easy enough, but mak sure you mark the cables to the motors. They don't like going from fast forward to slow reverse.

 

[netblindpaul]

Consider also the other requirements on control upgrades akin to the changes that would be required by BS7671 on a rewire.

 

[Knobhead]

What would you suggest Paul?

This sounds old kit and the owner will most likely baulk at the price for two new starters with the correct control voltage.
In my minds eye I can see the outcome. The starters will be moved still with one knackered contactor.
But you never know, miracles do happen and the owner will pay out.