FYI:
The
IEC definitions of voltage bands are:
- Extra Low Voltage: AC below 50V and DC below 120V
- Low Voltage: 50 - 1000V AC or 120 - 1500V DC
- Medium voltage: 1kV - 35kV
- High voltage: 35kV - 230kV
- Extra-high voltage: >230kV
This is not some pedantic technical point - if you start getting involved in doing your own electrical work, and start learning about regulations etc you'll come across references to "Low voltage", and it'll be no good you thinking that that means 12V...
Anyway.
If you just replace the 3 pendants with 3 downlighters the illumination will be terrible, because you'll be using lights which were not originally designed to light up rooms. They are often called spotlights, with good reason - they give out a narrow beam of light which is designed to highlight individual items or small areas. They were originally designed for retail display lighting, and are s***e at doing anything else.
If you install lots more to get around that problem then your electricity bill will be horrendous, and you'll still have brighter/dimmer areas where the beams overlap.
And in England or Wales it would be notifiable, which raises the problem of what do you do about the fact that you'd be in contravention of Part L.
With no access from above you'll also have another contravention of Part L because of the reduction in insulation, and as it's in a kitchen you may create a Part C contravention.
Depending on the depth of the roof, you may not have enough clearance for the lights, and if solid insulation has been installed you'll need to initially make large holes to get rid of enough, and then make good. On the ceiling around the lights you may then get condensation and, over time, dirty marks caused by convection currents.
Cable runs will be compromised by where the joists are and where they run, and again solid insulation may make installing extra cabling very difficult - removing and replacing the ceiling may be the only option. ELV currents are quite high so you'll need to watch the cable sizes carefully given de-rating factors caused by insulation and for voltage drop.
http://www.tlc-direct.co.uk/Book/4.3.1.htm
http://www.tlc-direct.co.uk/Technical/Lighting/VoltageDrop.html
Any screwed cable joints, e.g. junction boxes, transformer connections need to be accessible for maintenance and inspection, and transformers can be unreliable anyway.
So in short it could be a difficult job, it could cause you legal problems, it will be expensive to run, and the results will be s***e.