Let’s look at important things here –
Sun - Sun represents Personality, King, Government, Father, Authority, Career, Top Positions, Ego, Self Esteem, Health, Education etc.
Purva Bhadrapada Nakshatra - It is a nakshatra related with mystical events and experiences. It is also nakshatra of duality. Please check this link for more info on Purva Bhadrapada Nakshatra - https://www.astrosaxena.com/pbnaksha.
Aquarius - As Purva Bhadrapada is part of Aquarius sign, Aquarius and things represented by Aquarius are also important here. Aquarius is 11th sign of zodiac belt, hence it signifies the things and energy related with 11th house of horoscope, such as Gains, Desires, Hopes and Wishes, Large Organisations, Network Circles etc. Besides this, Aquarius also represents Scientific Thinking & Research, Uplifting the Society, Higher Goals & Rewards for all. Aquarius is made of another set of 2 and half Nakshatra, i.e. Dhanishtha, Satabhisha and Purva-Bhadrapada. Aquarius Lord is Saturn & Rahu.
Pisces - As Purva Bhadrapada is also a part of Pisces sign, Pisces and things represented by Pisces are also important here. As Pisces is the 12th sign of zodiac belt, it represents the same energy and things which are represented by 12th house such as Isolated Places, Spirituality, Imagination, Other Dimension or Other World etc. Besides these things, it also represents your Hidden Talents, Ability to work in background, Spiritual Self etc. Pisces is consisted of last 2 and half nakshatra, i.e. Purva-Bhadrapada, Uttara-Bhadrapada & Revati. Pisces' lord is Jupiter.
Saturn & Rahu - As Saturn-Rahu co-rule Aquarius, their position and dignity is important to know about the overall functioning of any planet in Purva Bhadrapada/Aquarius.
Jupiter - As Jupiter rules Purva Bhadrapada and Pisces, its position and dignity is important to know about the overall functioning of any planet in Purva Bhadrapada/Pisces.
Houses Involved – Also, we can’t afford to forget the houses involved as a planet can be ruling different houses and sitting in different house for every person as per ascendant and planet’s position. To know overall affect, we have to consider the houses involved as those areas of life are being impacted.
Interpretation of Sun in Purva Bhadrapada Nakshatra – This is one placement which can go on either extremes from highly spiritual or mystical to the biggest of trickster or scammer. Lot depends on how evolved is the soul of the person. It is mainly because of the representation of this nakshatra through a double-faced person. This shows that either they can be very spiritually evolved and completely devoted to spiritual/mystical pursuits or they can be the one who are showing-off to the people that they are spiritually evolved but actually they are not. They may use such an image for their material gains. So, this duality or split can stay with their personality. They can also be having dual career, means 2 totally different career at same time. It also shows that their real personality can be under cover every time and people may not have idea about their true self. They can be seen as spy or detectives or any kind of work related with secrecy. As it is ruled by Jupiter, the common significance of Jupiter as a teacher or guide comes with this placement but more in spiritual/mystical side of life. I think one differentiation we can make with this position is through the sign involved. In Pisces, person can be more spiritually evolved. In Aquarius, person can be more about making gains through serving society. But interpreting final result here is tricky if you don't have the full chart.
Role of Saturn & Rahu - Also, Saturn-Rahu placement is important to guide Sun in right direction, being Aquarius lords.
Role of Jupiter - Likewise, Jupiter placement is important to guide Sun in right direction, being Pisces lord.
Other Factors – And of course, we need to consider conjunction, aspects, house lordship, house position and dashas etc to know the exact results of Sun in Purva Bhadrapada. So, we always need to take a holistic view of chart rather than just 1 planetary position.
Conclusion – So, this is how I see Sun in Purva Bhadrapada can work in a chart.