Toshiba Tosvert VF-AS1 - Manual (Page 87)

E6581301
E-21
5
5.14 Setting the electronic thermal
VJT : Motor electronic thermal protection level 1
QNO : Electronic thermal protection characteristic selection
H : Overload reduction starting frequency
H : Motor 150%-overload time limit
H : Inverter overload selection
[Parameter setting]
Title Function Adjustment range Default setting
VJT
Motor electronic
thermal
protection level 1
~%
Default
setting
Motor type
Overload
protection
Overload stall
{ (protect) × (not stall)
{ (protect) { (stall)
× (not protect) × (not stall)
Standard
Motor
× (not protect) { (stall)
{ (protect) × (not stall)
{ (protect) { (stall)
× (not protect) × (not stall)
QNO
Motor overload
protection
characteristic
selection
VF
Motor
(special
motor)
× (not protect) { (stall)
1) Setting the motor overload protection level 1 VJT and electronic thermal protection characteristics
selection QNO
The electronic thermal protection characteristics selection QNO is used to enable or disable the motor overload trip
function (QN) and the overload stall function.
The motor overload trip function (QN) needs to be selected with the parameter QNO, while the inverter overload
trip function (QN) is always activated.
[Using general-purpose motors (other than motors intended for use with inverters)]
When a motor is used in the lower frequency range than the rated frequency, that will decrease the cooling effects
for the motor. This speeds up the start of overload detection operations when a general-purpose motor is used in
order to prevent overheating.
■
Setting of electronic thermal protection characteristics selection QNO
Default setting Overload protection Overload stall
{ (protect) × (not stall)
{ (protect) { (stall)
× (not protect) × (not stall)
× (not protect) { (stall)
• Function
This parameter allows selection of the appropriate electronic thermal protection characteristics according to the
particular rating and characteristics of the motor.
Explanation of terms:
Overload stall (Soft stall)
The function of automatically lowering the output frequency before the motor overload trip function
QN
is activated when the inverter detects that an excessive load is applied to the motor. (Lowers
maximum about 48Hz when basic frequency is 60Hz.) This function enables the inverter to output a
frequency commensurate with the load current so that the motor can keep running without tripping.
This function is useful for such loads as fans, pump, and blowers, which have the square reduction
torque characteristic that the current passed decreases as the rotating speed falls.
Note:Do not use this overload stall function for loads with a constant torque characteristic (e.g., a belt
conveyer to which a constant load current is always passed regardless of their speed).