Acceleration And Deceleration Times (Pr. 7, Pr. 8); Electronic Thermal Overload Relay (Pr. 9) - Mitsubishi Electric FR-A800 Series Beginner's Manual

Parameter
6.2.5

Acceleration and deceleration times (Pr. 7, Pr. 8)

One of the big advantages of frequency inverters is that they can accelerate and slow down the con-
nected motor gradually. Electric motors connected directly to the mains power accelerate up to their
maximum speed very rapidly; this is often not desirable, particularly for machines with delicate me-
chanical parts.
Parameters 7 and 8 allow you to adjust the acceleration and deceleration times. The parameter value
defines the acceleration or deceleration period. This means that the speed change per unit of time
gets smaller as you increase the value.
Parameter 7 sets the acceleration time for the drive. The value defines the time in seconds in which the
drive will be accelerated up from 0 Hz to the frequency preset in parameter 20.
Parameter 8 sets the deceleration time, which is the time in seconds in which the drive will be slowed
down to 0 Hz from the frequency preset in parameter 20.
6.2.6

Electronic thermal overload relay (Pr. 9)

Mitsubishi's frequency inverters have an internal electronic thermal overload relay to protect the mo-
tor. The motor's frequency and current are monitored in relation to its rated current and if the values
rise too high the protection function is activated. This function serves primarily to protect the motor
against overheating during operation at low speeds and high torques. The reduced cooling function
of the motor's fan at low speeds and other factors are also taken into account.
Enter the motor's rated current in parameter 9. You can find this value on the motor's rating plate.
You can deactivate the thermal overload relay by setting parameter 9 to „0" (for example if you are us-
ing an external motor protection device or if multiple motors are connected to the inverter). Deacti-
vating the relay will not turn off the overload protection feature for the frequency inverter's own tran-
sistors.
Frequency Inverters - Beginner's Guide
Acceleration time Deceleration
(Pr. 7) time (Pr. 8)
The simple mode parameters in detail
6 - 5