MaxSpeed

General

Functional Description

The parameter represents the maximum motor rotational speed in RPM (revolutions per minute). The value of MaxSpeed depends on the motor type and the encoder used. The definition to determine the value of the MaxSpeed is the minimum of:

o90 % of the maximum permitted motor rotational speed

o90 % of the maximum permitted encoder rotational speed

othe rotational speed, which theoretically can be reached at a bus voltage of 780 Vdc even though the bus is limited by the nominal voltage of the drive

oIn Voltage/Frequency control mode for asynchronous motors, the controlled output frequency is limited to 599 Hz. The outcome of this is a limitation of the MaxSpeed, which is calculated as follows: MaxSpeed = 599 Hz * 60 / number of pole pairs.

By default the parameter MaxVel contains the velocity value of the rated speed (when UserMaxVel = 0).

A shutdown occurs when the limit speed is exceeded at 111.1 % of MaxVel.

If a motor has MaxSpeed < NominalSpeed (for example, because the encoder rotational speed is too low), then the motor cannot be operated with the rated speed. In this case, the default value of MaxVel [units/seconds] is the velocity of MaxSpeed [RPM].

NOTE:  If the rated speed is exceeded, then the motor picks up less current by increasing rotational speed. The amplitude of the current depends on the momentary voltage in the DC bus. The current is reduced until a further increasing of the speed is not possible anymore. Depending on the induced voltage of the motor used, it is possible that MaxSpeedLinear cannot be reached (the typical DC bus voltage on a 3-phase 400 V network is 560 V, even though MaxSpeedLinear requires up to 780 V). Verify that enough voltage/current is available for the speed requirements of your application (see Drive sizing with Motion Builder).

NOTE: The parameter value is transferred from the slave to the master via the parameter channel of the Sercos by every access. Typically, this takes about 10 ms. However, up to 1 s can be realized if large amounts of data are transferred on the parameter channel. If the Sercos bus is in phase 0 or 1, then a default value is indicated here. If the Sercos bus is in phase 3 or 4, then the parameter value is transferred and indicated. In the Sercos phase 2, the parameter can be read through the application.