Toshiba VF-nC1 instruction manual Setting the electronic thermal, Explanation of terms

E6581090

5.10Setting the electronic thermal

QNO : Electronic thermal protection characteristics

VJT : Motor thermal protection level 1 (%)

• Function

Selects the electronic thermal protection characteristics that fit with the ratings and characteristics of the motor.

■Parameter setting

Title	Function		Adjustment range			Default setting
		Setting		Overload	Overload
		value		protection	stall
		0		○	×
	Electronic thermal	1	Standard	○	○		5
		2	motor	×	×	0
QNO	protection
		3		×	○
	characteristics
		4	VF motor	○	×
		5		○	○
			(special
		6		×	×
			motor)
		7		×	○
VJT	Motor thermal	30～100 (%)				100
	protection level 1 (%)

★ ○ : valid, × : invalid

1) Setting the electronic thermal protection characteristics selection

motor electronic thermal protection level 1 VJT

QNO and

The electronic thermal protection characteristics selection QNO is used to enable or disable the motor overload trip function (QN) and the overload stall function.

While the inverter overload trip (QN) will be in constant detect operation, the motor overload trip (QN) can be selected using the parameter QNO.

Explanation of terms

Overload stall : When the inverter detects an overload, this function automatically lowers the output frequency before the motor overload trip QN is activated. The soft stall function allows the drive to run with balanced load current frequency without a trip. This is an optimum function for equipment such as fans, pumps and blowers with variable torque characteristics that the load current decreases as the operating speed decreases.

Note: Do not use the overload stall function with loads having constant torque characteristics

(such as conveyor belts in which load current is fixed with no relation to speed).

[Using standard 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 standard motor is used in order to prevent overheating.

■Setting of electronic thermal protection characteristics selection QNO

Setting	Overload	Overload
value	protection	stall
	○	×
	○	○
	×	×
	×	○

○: valid, × : invalid

■Setting of motor electronic thermal protection level 1 VJT

If the capacity of the motor is smaller than the capacity of the inverter, or the rated current of the motor is smaller than the rated current of the inverter, adjust the electronic thermal protection level 1 VJT so that it fits the motor's rated current.

E-9