Contactor selection 1

[bahram]

I want to use a Telemechanique D9 contactor for
interruption of DC loads as follows:

1- 24VDC, 0.5A, ( one drain diode is mounted at outgoing terminal)
2- 220VDC, 40mA

Since I do not have information from DC interruption capacity of both main contact and auxiliary contact of such contactor type, please help me to this respect.

 

[r19h72]

Hi bahram,
the problem with dc is the missing zero-point. So if you break the line the current should find an alternative path to continue until it goes to zero. I hope that's the way you use the diode.
A reduction-factor of 10 for the AC-rating of the contactor will then be save.

hanness

 

[bahram]

Dear Hannes
thank you for reply
the reduction factor of 10 can give me a quite sufficient margin to break the loads. as I understood this factor is practical ,so is there any standard describing this relation or is there any evidence in technical literatures or catalogues?

 

[MDom]

Hi bahram, you can find this information in Telemecanique catalogue Contactors ( for example July 98) page1/30. The rated current depends on categories of utilization - DC1 to DC 5 . For the DC-2 to DC-5 you have
12 A for 24 V DC - I mean the contactor LC-1,LP-1 - D09.
If you connect 3 poles in series you can obtain 18 A at 24VDC. Of course it's better to connect the main contact in
series.
For 225 VDC you can use LC-1 D09 for the current 0.75A - one pole and up to 6 A for three poles in series.
Our experience shows that it's difficult to interrupt the
DC by the contactor if you have more than 75 V/per pole.
It's not an official information from the manufacturer,but
our practical information.It's necessary to add that I mean the current in tens A and more,but not 0.4 A.
In any case it will be better to connect the poles in series for 225 VDC.
As for auxiliary contact,you can find their characterisics
for category DC-13 on page 1/91 the a/m catalogue.
For 1 million operating sycles the permissible interrupted power for 24 VDC is 120 W - 5 A , for 220VDC - 68 W hence
0.3 A