Watlow Power Series Rev H - Manual (Page 9)

I n s t a l l a t i o n , C h a p t e r 2 Wa t l o w P o w e r S e r i e s ■ 2 . 3
Enclosure Guidelines
The Power Series must be mounted in a suitable electrical enclosure. It must
have adequate wire bending space and cooling. The maximum ambient
temperature in the enclosure must not exceed 50°C (122°F) for name plate
rating. For other output ratings and enclosure ambient temperatures, see output
rating curves on pages 2.5 and 2.6.
To maintain the proper cooling, the enclosure must be large enough to dissipate
the heat generated by the Power Series, or there must be some form of active
cooling.
1. Air circulation — fans bring air into the bottom of the enclosure and louver
plates to allow the air to exit the top of the enclosure. Filters are not
recommended as they can become plugged and block air flow. To maintain
80 percent of the CFM of a fan, the outlet must be four times the area of the
fan inlet. Ensure that each Power Series is within an unobstructed
airstream.
2. Vortex coolers operate on compressed air and provide good cooling on a
sealed enclosure, but are noisy and consume a lot of air.
3. Cabinet air conditioners work well on sealed enclosures.
4. Heat pipe coolers work well on sealed enclosures, but do not provide as
much cooling as vortex coolers or air conditioners.
To determine how much cooling is required:
1. Determine the amperage load on the Power Series. Multiply the amperage by
1.2 and then by the number of phases controlled. This is the output power
dissipated by the SCRs in watts. Add the watts dissipated by the controller’s
power supply (21W) and multiply the total power in watts by 3.41 to get
BTUs per hour. Vortex coolers, heat pipe coolers, and air conditioner cooling are
rated in BTUs removed.
2. Add up the watts generated by other electronics in the enclosure and
multiply by 3.41 to get BTUs per hour.
3. Add up the total BTUs inside the enclosure and pick a cooling device that will
remove that amount of BTUs.
4. For fan cooled enclosures, enclosure and fan manufacturers usually have
free software programs and application notes to help size the fans for
enclosures. If necessary, contact the Application Engineers at Watlow
Controls for assistance.
Harsh Environment
The Power Series meets standards UL508, Pollution degree 3 for safety which
states: “Conductive pollution occurs or non-conductive pollution occurs which
becomes conductive due to condensation which is to be expected.” However,
Watlow recommends that the Power Series be used in a clean, dry environment
to ensure long-term reliability.