Delta Electronics AC Motor Drive VFD-EL - Manual (Page 118)

Chapter 4 Parameters|
Revision August 2008, 2ELE, V1.02 4-75
AVI
ACM
+10V
PTC
VFD-EL
47kΩ
resistor-divider
R1
internal circuit
Refer to following calculation for protection level and warning level.
1. Protection level
Pr.07.14= V
+10
* (R
PTC1
//47K) / [R1+( R
PTC1
//47K)]
2. Warning level
Pr.07.16= V
+10
* (R
PTC2
//47K) / [R1+( R
PTC2
//47K)]
3. Definition:
V+10: voltage between +10V-ACM, Range 10.4~11.2VDC
R
PTC1
: motor PTC overheat protection level. Corresponding voltage level set in Pr.07.14,
R
PTC2
: motor PTC overheat warning level. Corresponding voltage level set in Pr.07.15,
47kΩ: is AVI input impedance, R1: resistor-divider (recommended value: 1~20kΩ)
Take the standard PTC thermistor as example: if protection level is 1330Ω, the voltage
between +10V-ACM is 10.5V and resistor-divider R1 is 4.4kΩ. Refer to following calculation
for Pr.07.14 setting.
1330//47000=(1330*47000)/(1330+47000)=1293.4
10.5*1293.4/(4400+1293.4)=2.38(V) ≒2.4(V)
Therefore, Pr.07.14 should be set to 2.4.