Without doubt, the most obvious intention of the Separation of Powers is to provide a checking, restraining, controlling influence on Government. Political commentators generally accept that the checks and balances are there to protect Liberty and prevent tyrannical rule. However, as important is its purpose in creating a good, competent government, with the people's consent. This is achieved by the Constitution by attracting people to the job and allowing them to be elected only if they are suitable for the job. This may seem untrue in present situation, but the way in which a President is elected reflects how his/her term in office should be run: Making friends, persuading, fund raising, public speaking. These attributes will be found in most Presidents. The system assumes a potential President is driven by ambition seeks "public honour" and will not pursue a regime of self-interests. Therefore the Constitution looks to exploit this in a President. .
The Congressional elections varying terms and election years make for a group of people who learn to do their job well while representing the public mood and their constituents. The Senate's staggered election, in particular, adds stability to the process; hopefully outdoing mood-bias in a short period. The President's terms of office call for speed, secrecy and popularity; attracting to the position therefore, people with "energy", who are robust and reflect the public opinion. The unlimited terms of office for the Supreme Court are expected to attract "able and ambitious characters to those offices". This is because the office gives the holder opportunities for governing well. .
So the aim of "Separation of Powers" is not to provide separate institutions sharing power, but each branch is give a specific kind of power. Each of the three branches then makes a specific contribution to Governance. From the Framers" Point of view, they were intending to create a system that would encourage Federal Government.