116 The internal cooling circuit
Maintenance
Filling up and bleeding the internal cooling circuit
Converter line-ups with a customer cooling unit
Both the converter and coolant must be at room temperature before filling in the cooling
circuit.
WARNING! Ensure that the maximum permissible operating pressure is not
exceeded. When necessary regulate the pressure to appropriate level by draining
excess coolant out of the system.
WARNING! Bleeding of the cooling circuit is very important and has to be done
with great care. Air bubbles in the cooling circuit may reduce or completely block
coolant flow and lead to overheating. Let the air out of the cooling system while
filling in coolant and, eg, after any power module replacements.
Notes:
• The bleed valves in the line-up are used only to vent the air from the circuit so that it
can be displaced by the coolant. The actual bleeding of the circuit must be done via an
external bleed valve installed at the highest point of the cooling circuit. The most
practical location for the valve is usually near or at the cooling unit.
• Observe the instructions given by the manufacturer of the cooling unit. Pay special
attention to filling up and bleeding the pumps properly as they may be damaged if
operated when dry.
• Draining liquid into the sewer system is not allowed (it may contain harmful
substances like propylene glycol).
1. Open the main bleed valve at the cooling unit.
2. Open the inlet, outlet and bleed valves of one converter cubicle.
3. Lead the bleed hoses into buckets or other suitable containers. Extend the standard
hoses if necessary.
4. Fill the circuit with coolant. For coolant specification, see below.
5. After the converter unit is filled up, coolant will start flowing from the bleed hose of the
converter cubicle. Let some coolant flow out before closing the bleed valve.
6. Close the inlet, outlet and bleed valves of the converter cubicle.
7. Open the inlet and outlet valves in converter cubicle. Let any air remaining in the
system out through the bleed valve at the cooling unit.
8. Close the bleed valve at the cooling unit.
9. Continue to fill in coolant until a base pressure of 100…150 kPa (1…1.5 bar) is
achieved.
10. Open the bleed valve of the pump to allow any air out.
11. Re-check the pressure and add coolant if necessary.
12. Start the coolant pump. Let any air remaining in the system out through the bleed
valve at the cooling unit.
13. After one to two minutes, stop the pump or block the coolant flow with a valve.
14. Re-check the pressure and add coolant if necessary.
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