Braking relais

The motors with brake we use, mostly have a brake on DC.
Inside the connectionbox of the motor there is a rectifier from 230V AC to DC. We always use a Releco relais C7 with two contacts (http://www.releco.es), where one contact interrupts the 230V on one wire and the DC-current also on one wire.
I have seen some cases where the relais was welded after one year. I have been thinking about more powerfull relais or even solid states.
What do you use as braking relais? How do you cut the current to the brake?

Think I would break both sides of AC line to brake rectifier. AC is a bit easier to interrupt without arcing than is DC. I would also think about putting a rectifier across the brake coil to bleed off the current from collapsing field. May not be needed since rectifiers will block that from contacts but it sure wont hurt to do it.

Dan Bentler

Plc_User said:

I have seen some cases where the relais was welded after one year. I have been thinking about more powerfull relais or even solid states.

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You need a IEC "DC3" rated relay

milldrone said:

You need a IEC "DC3" rated relay

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Do you have a specific example?

Plc_User said:

Do you have a specific example?

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I'm sure there are others.

http://www.abb-control.com/pdf/catalog/lv023/1.42.pdf

Here is another.

http://www.automation.siemens.com/m...elays-miniature-contactors/Pages/default.aspx

Note the increase in amperage (DC3 load category) when using more than one contact in series.
http://www.promspecrele.ru/documents/LV1T_3TG10.pdf