You asked,
is it common to increase the standard raise?
Yes - it's fair to say that people generally expect an increase when they get a promotion, in addition to any increase that is given annually (typically for "expected" growth and/or cost of living increases).
If so, by how much?
It may be helpful to step back and determine how your employer determined the salaries employees are already paid. Hopefully, that was done by essentially pricing out the job description - in other words, determining the market rate for the work that's being accomplished. Although, for some employers, it may have been much less intentional than that. But at the end of the day, pay is usually tied to the responsibilities of the position.
Understanding that gives you a default process by which you can answer your own question. If you have a team of people with Junior title, and you're wondering what the pay them once they're promoted to Middle or Senior titles, you first need to determine what the differences in responsibility, skills, and expectations are. Then, you can just iterate your original process. We can't tell you if a Senior is worth 5% more or 50% more than a Middle title, but you can determine that once you have a documented job description for both, and are able to quantify the differences.