A/B Stepper Card (1746-HSPT1) getting really hot!!

[SCADA_Dude]

I have a 7 slot rack with 4 A/B 1746-HSTP1 stepper cards (Plus 1 DI, 1 DO & SLC 5/03). I have a 90W 24V DC supply connected to the cards to supply power for the cards IO, along with various other devices in the panel (Other I/O cards, switch, protocol converter, etc).

After about 5 minutes the four stepper cards are getting VERY hot up on top. The DO card which also is powered from the same supply is not hot at all. I removed one of the cards and the hot spot is the heat sink for the voltage regulator. According to the manual, these cards can handle 24VDC 09A Max.

I removed 3 stepper cards and hooked up 24VDC from the Rack P/S (P1) to the one stepper card and the card does not get hot, which confirms my suspicion that the card is getting to much current. I tried to wire all four cards to the Rack PS, but the voltage sags to 4 VDC.

I am using a 90W 24VDC Rhino PS (PSM24-090S) from Automation Direct, which I think is a switching power supply. Do I need a small 24VDC power supply just for these cards or is this normal? It seems like something is not right, as I can barely hold my hand on the cards. Any ideas would be greatly appreciated!

BTW, the cards operate fine so I don't think its a bad card or mis-wiring etc.

Thanks

 

[Sergei Troizky]

I've used the mentioned cards and they never needed anything distinct among other 1746 cards.
Never had overheating problem, but obviously this card should heat up more than a regular I/O one.

 

[SCADA_Dude]

I just noticed that the 1746-P1 power supply is actually overloaded (by 75mA) with the IO configuration I am using. I will try a 1746-P2 to see if that helps.