AC TRACTION – MOTOR SET-UP EXAMPLE PG DRIVES TECHNOLOGY
Ensure the values of 1.4 Maximum Forward Speed and 1.5 Maximum Reverse Speed are lower
than the Motor Speed Maximum setting. If the actual motor speed is higher than this value, the
Sigmadrive is out of control and will trip with an ‘F30’ error.
1.2 Drive voltage set-up
The drive voltage set-up is linear from the Motor Speed Minimum value to the Motor Speed Boost value.
The parameters, 4.11 Drive Voltage Boost, 4.12 Drive Voltage Base and 4.13 Drive Voltage Maximum should be set to the rated
voltage shown on the label i.e. 34Vrms.
If the motor is rated at 34Vrms, the battery supply should be at least 48V (34Vrms * √2 = 48V). However, in practice, if the battery
is a little low and losses in the battery cable, motor cables and controller are taken into account, the actual voltage available
could be lower, perhaps around 30Vrms. Above the value of 4.6 Motor Speed Boost, the voltage can no longer be increased, as
there is no higher ‘rms’ voltage available from the battery supply. Therefore, the voltage levels at boost speed, base speed and
maximum speed are normally set the same.
The parameter 4.10 Drive Voltage Minimum should be set to about 10% of the rated motor voltage.
The final value of the parameter 4.9 Minimum Voltage will depend on the application. If this is set too high then there will be high
motor currents in neutral, which will heat up both the motor and controller. Initially, the value for this parameter should be set to
0.5Vrms enabling a minimum starting torque at zero speed.
Therefore, in this example the drive voltages should be programmed as follows.
• Minimum Voltage: 0.5Vrms
• Drive Voltage Minimum: 3.4Vrms
• Drive Voltage Boost: 30Vrms
• Drive Voltage Base: 30Vrms
• Drive Voltage Maximum: 30Vrms
1.3 Drive slip set-up
The drive slip can also be calculated from the motor label information. In this example, the rotor speed is 1280 rpm at nominal
power. First convert the rotor speed from rpm to Hz using the following rules.
There are 3 types of motors; 2 pole, 4 pole and 6 pole.
For 2 pole motors the rotor speed must be divided by 60.
For 4 pole motors the rotor speed must be divided by 30.
For 6 pole motors the rotor speed must be divided by 20.
Most motors, like the one in this example, are 4 pole. This gives a value of 42.66 Hz (1280 rpm / 30). Using this value the slip
setting from minimum speed to base speed can be calculated as 1.33Hz (44Hz – 42.66Hz). With this slip at base speed and
190A motor current we have an 8kW output. For acceleration and to climb a ramp we need more power than the 8kW. As the
base speed is already programmed to the maximum motor voltage available, 30Vrms, the only possibility to achieve the
required power is to increase the current, thereby increasing the slip. An ACT445M Sigmadrive can provide 320Arms motor
current (450A / √2).
The slip at Boost, Base and Maximum speed can now be calculated. In this example the Motor Speed Base point is at 44Hz.
Using the following formula, the value for maximum slip can be calculated.
Maximum current (320Arms) / Nominal current (190Arms) * Nominal slip (1.33Hz) = Maximum Slip (2.24Hz)
This slip setting, 2.24Hz is used for the parameters Drive Slip Boost, Drive Slip Base and Drive Slip Maximum. The parameter Drive
Slip Minimum is set to 70% of the Drive Slip Base value. The relationship between current and slip is not linear but this set-up is
usually a good starting point for a safe first test.
Therefore, in this example the settings would be as follows.
SK79646-01 68
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