L3-04: Stall Prevention during Decel

No. (Hex.)	Name	Description	Default (Range)
L3-04 (0492)	Stall Prevention during Decel	Sets the method that the drive will use to prevent overvoltage faults when decelerating.	1 (Determined by A1-02)

Stall Prevention during deceleration controls the deceleration as specified by the DC bus voltage and does not let high inertia or fast deceleration cause ov [Overvoltage] faults.

0

Disabled

The drive decelerates as specified by the deceleration time. If the deceleration time is too short, the drive can detect an ov fault.

Note:

If an ov fault occurs, connect a dynamic braking option to the drive. If an ov fault occurs when you connect a dynamic braking option and A1-02 = 0 or 2 [Control Method Selection = V/f or OLV] and L3-04 = 0, set L3-04 = 3.

1

General Purpose

The drive decelerates as specified by the deceleration time. When the DC bus voltage is more than the Stall Prevention level, the drive stops deceleration until the DC bus voltage is less than the Stall Prevention Level. The drive then starts to decelerate at the set deceleration time. Frequent use of Stall Prevention will help prevent ov faults when the deceleration time is shorter than the drive can usually accept.

Note:

The Decel Stall Prevention function will increase the deceleration time to stop and the deceleration time will be longer than the setting. This function is not applicable for conveyor applications because the precision of the stop position is very important. As an alternative, use a dynamic braking option in these applications.

The input voltage setting of E1-01 [Input AC Supply Voltage] sets the DC bus voltage level for Stall Prevention.

Table 1. Stall Prevention Level during Deceleration

Drive Input Voltage	Stall Prevention Level during Deceleration
200 V Class	377 V
400 V Class	754 V

Figure 1 shows the Stall Prevention during deceleration function.

2

Intelligent (Ignore Decel Ramp)

The drive adjusts the deceleration rate to keep the DC bus voltage at the L3-17 [DC Bus Regulation Level] level. This makes the shortest possible deceleration time and will not let the motor stall. The drive ignores the selected deceleration time and the possible deceleration time cannot be less than 1/10 of the set deceleration time.

This function uses these parameters to adjust the deceleration rate:

• L3-20 [DC Bus Voltage Adjustment Gain]

• L3-21 [OVSuppression Accel/Decel P Gain]

• L3-24 [Motor Accel Time @ Rated Torque]

• L3-25 [Load Inertia Ratio]

Note:

The deceleration time is not constant. For applications where the precision of the stop position is very important, use a dynamic braking option and set L3-04 = 0. If an ov occurs, set L3-04 = 3.

3

General Purpose w/ DB resistor

A braking resistor is necessary for this setting. The braking resistor and the drive work together for the Stall Prevention during deceleration function.

4

Overexcitation/High Flux 1

Enables Overexcitation/High Flux and enables a shorter deceleration time than when L3-04 = 0.

Note:

• If the overexcitation time is long and you decelerate frequently, the drive can detect oL1 [Motor Overload] faults. If the drive detects oL1, decrease the deceleration time or install a braking resistor to the drive.

• The deceleration time during Overexcitation Deceleration changes when the motor characteristics and machine inertia change. Adjust the n3-13 [OverexcitationBraking (OEB) Gain] and n3-23 [Overexcitation Braking Operation] levels. Refer to Overexcitation Deceleration for more information.

5

Overexcitation/High Flux 2

Enables Overexcitation/High Flux 2. This function decreases the possible deceleration time more than Overexcitation/High Flux.

The drive decreases motor speed and tries to keep the DC bus voltage at the L3-17 level.

If the drive detects oL1, decrease the values set in n3-13 and n3-21. If the drive detects ov, increase the values set in C1-02, C1-04, C1-06, and C1-08 [Deceleration Times].

Note:

• During Overexcitation/High Flux 2, the drive disables Hunting Prevention in V/f Control and also disables Speed Control that uses torque limit in OLV Control.

• Refer to Overexcitation Deceleration for more information.

7

Overexcitation/High Flux 3

If you set L3-04 = 7 [Overexcitation Braking 3], the overexcitation increases compared with 4 [Overexcitation/High Flux]. This can decrease the deceleration time.

Note:

When L3-04 = 7, the overexcitation current increases as compared with 4. Motor load becomes larger, and it can cause oL1 [Motor Overload]. When you can use L3-04 = 4 to operate the drive, set L3-04 = 4.