Why does a 240VAC/24VAC 50VA transformer draw decreasing current on 48V DC supply?

i need to connect a 48V DC to an inductive load so i used a transformer's primary as the load with the secondary open. i need a constant 1A draw by the load but when i used the transformer the current starts from 1.8A and drops to 1.04A but it takes 15mins to reach that value. is there a reason behind this? transformer rating: 240VAC/24VAC, 50VA, 60HZ