what do u need to rpair t-b1 power armour u get from fort constaine . thx in advance

From traders i guess.
I guess you can repair em with normal power armor too.
I don't like that armor though i think it's overpowered.

If you do not mind glitching, then head over to Point Lookout and visit 'Haley's Hardware'. Enter the shop, exit, run to the river and enter store again. Haley's Repair skill will increase by 5 points each time until it reaches 100, which means he can repair any of your items.

But if you don't have access to Point Lookout, then I suggest you invest in the caravan trader Crazy Wolfgang. Do this by speaking to Uncle Roe at Canterburry Commons. Wolfgang's skill will be boosted to 75, though you can increase it a little more by reverse-pickpocketing clothing which gives a bonus to Repair.
By doing this method, you still won't be able to repair the T-51b to perfect condition, however. But I'm led to believe it's the best you can do in the vanilla game.

God bless the Enclave.

thx but one more question is there any other unique power armour and is it better to use the englave hell fire armour , t-1b armour or winterized t-1b armour

Yes, I believe there are other unique Power Armours, such as Lord Ashur's from The Pitt.

Out of the three armours you mentioned, I'd definitely say regular T-51b is the worst. It's got great DR, sure, but visually it looks terrible (or at least I think so) and cannot be repaired to 100% without glitching. Hellfire Armour on the other hand is just as durable, can be repaired, has Fire Resistance, and doesn't look old and rusted. Plus, it's the armour of the Enclave -- what could be more honourable than representing the saviours of America?

Wintersized T-51b is great, too. It could be directly hit by a nuke and still remain unscathed, and the armour sure does look badass, too. The only downside is that its total DR is 5 points less than the other two.

Winterized armor and t1 b is the same.
Hellfire is the coolest and most baddasest armor evar.

thx ill definetly use the hell fire armour

Don't forget the +1 Strength. Thus, while it may weigh 40 units (not including the helmet), it actually weighs 10 units less when worn.