SYSTEMAIR

SYSTEMAIR
Chapter II
Motor protection
Most fans have an integral thermal protection relay which provides the motors with better protection against overheating than an overcurrent protection relay.This is especially important if the fan is speed controlled by means of voltage reduction as it a then impossible to stipulate the precise over-current. The thermal contact are fitted in the motor winding it will open and disconnect the power supply to the fan when the critical temperature is reached.This is 130ºC for motors with insulation class B and 155ºC for motors with insulation class F.
Integral thermal contact
Fans with integral thermal are reset either automatically or manually by switching off the current and then wait for up to an hour before the fan can be started again.
External leads from thermal contact
Fans with external leads from the thermal contact are supplied with two leads connected to the integral thermal contact.These leads must always be connected to a motor-protection relay.
The S-ET 10 is suitable for single phase fans for the AWE-SK if the current is below 0.45A and the STDT -16 is suitable for three phase fans .If the thermal contact has opened the protection relay must be reset manually.
Thermal contacts that can be reset electrically
If a fan is better with a thermal contact that can be reset electrically one must first switch off the current and then wait for up to an hour before the fan can be started again.KVLF and small KD fans are among those models which require electrical resetting.
Rated current
Rated current means the maximum current used by the fan from the mains supply at nominal mains voltage .When the fan the current in the motor may exceed the specified rated current when the voltage is low .The increased current in the motor requires a reduction of the maximum permitted temperature for transported air in the technical tables the highest permitted temperature for transported air is shown for both the rated current and for speed control.
Air flow
The air flow is shown for free blowing conditions . Air flow is measured in accordance with DIN 24 163 and BSA BS 848 .Assumed air density is 1.2 kg/m3 at 20ºC.
Pressure
The static pressure is shown in the fan diagrams as ps( Pa )