Attic fan

I've a whole house attic fan mounted on roof top. The motor has been burnt for this fan as per the electrician. Is it good idea to change/replace the motor or it's advisable to change the entire attic fan ?

One of the electrician suggested that changing motor meight burnt again if it's not properly mounted or balanced, so it's better to change the fan, but it's costing me a lot by changing the entire fan.

Pl. suggest what should I do. Help will be appreciated.

Thx in advance.