Functions; Voltage Protection; Compressor Protection Against Short Cycling; Zero Cross Technology - Danfoss EET Series User Manual

Refrigeration controller, type EET series

Functions

Voltage protection

The voltage protection feature protects the compressor against high and low voltage fluctuations by limiting the
compressor operation within specified voltage limits. Whenever the supply voltage goes beyond the defined
voltage limits set in the controller, it will switch the compressor OFF, and resume the operation when the voltage
falls under the operating range.
Figure 1: Voltage protection
uHi
V
uLi
uLo

Compressor protection against short cycling

This feature protects the compressor from short ON-OFF cycles. The EET controller ensures that the compressor is
switched ON and OFF for a minimum time specified under Minimum run time (Crt) and Minimum stop time (cSt)
except during voltage and condenser protection.
Figure 2: Compressor protection against short cycling
min. run time
ON
OFF
min. stop time
CUT-IN
CUT-OFF

Zero Cross Technology

The Zero Cross Technology controls the relay's switching time by ensuring that the relays switch ON or OFF close to
the 0th position of the voltage curve. This ensures reduced relay contact welding, increased relay life and reduced
switching noise. This feature should only be used when the compressor is directly driven by the EET relay and no
external contactor is used.
© Danfoss | Climate Solutions | 2023.07
uHi Maximum voltage limit above which the
compressor is switched off
V Supply voltage
uLo Minimum voltage limit below which the
compressor is switched off
uLi Minimum voltage limit above which the
compressor can start
time
time
BC320944106159en-000301 | 5