Need Help!- why do relays get hot

[contactirfu]

olks - when building the new controls for my machine - i face a peculiar problem.

One of the 220v relays is getting heated up.
the relay is rated at 220V and that is supplied to it via a relay (used for estop) 24v - the 220v relay inturn switches on off the 24v timer which is used to bypass the 50-OHM resistor on the main supply to the supply transformer TR1

any ideas and help are welcome.

I will post pictures of my controller build soon.

otherwise follow my UHU controller build here -

http://www.cnczone.com/forums/showth...=60710&page=15

RGDS
Irfan

[Al_The_Man]

There is only a couple of reasons an AC relay will heat up.
If it does in fact have full voltage of 220vac across the coil, then if the relay armature does not pick up fully for any reason, the impedance of the coil drops dramatically causing high current, this does not happen in DC coil relays.
The other less likely reason is to under-rate the contact current carrying rating of the relay.
You may either have a defective relay or something is preventing the armature from closing completely.
Al.

[contactirfu]

Al - I dont exactly have have 220V in the relay coil - its like between 190 and 210v AC.

will that matter?

in fact I have only 24V 1 amp being switched. while the relay contact is rated at 220V 10 AMPS

Thanks for the reply AL -

RGDS
Irfan

[Al_The_Man]

Then it is not the contact switching current, so that leaves the coil.
If the coil voltage drop too low, then it can cause the armature to not become fully sealed in, and this will cause the effect I mentioned.
Is this an open-frame relay or encased in a cover?
If open frame, you can physically see if there is any movement after pull in by pushing on the armature after it is energized.
Also if the mating surfaces of the coil core and the armature are rough or not exactly parallel, this can do it.
Do you have the spec as to what the coil wattage should be?
Al.

[contactirfu]

the relay is encased in a cover. however the relay has a transparent cover. I tried to switch it at home where power is more near 220V still it heats up like anything,

the relay is something like this

RGDS
Irfan

[Al_The_Man]

Those are normally very low wattage, so I would say you either have a defective relay or possibly the wrong coil was put on during assembly.
Al.

[contactirfu]

It was a defective relay - infact the whole batch which my supplier had ordered were defective - I have got better ones now.

Al thanks for the support.

RGDS
IRfan