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E300 Design Guide 231
Issue Number: 1
1: Non-salient
If the ratio Lq/Ld < 1.1 on no load then the injection mode cannot be used and this mode should be used instead. This mode does not provide the
same level of control as injection mode and has the following restrictions:
1. Speed control is possible, but not torque control.
2. Spinning start is not possible and the motor must start from standstill.
3. Below Motor Rated Speed (B07) / 10 it will not be possible to produce more than approximately 60 % to 70 % of rated torque.
4. There may be some movement of the motor shaft in either direction as the motor starts.
5. It is not possible to measure the motor inertia using auto-tuning with Motor Autotune (B11) = 4.
6. Normally the ramp rate should not be slower than 5 s/1000 rpm when operating in the region below Motor Rated Speed (B07) / 10.
7. This mode is not intended to control the motor for prolonged periods below Motor Rated Speed (B07) / 10, but is intended to allow the motor to
be started from standstill to run outside the low speed region.
8. This mode is not intended to allow motor reversals. If the direction does need to be reversed, the motor should be stopped and any oscillations
must die away, before the motor is restarted in the other direction.
Sensorless Mode Low Speed Current (C16) defines a current applied in the motor d axis to aid starting. The default value is suitable for most motors
with a load of up to 60% rated torque. However, in some applications this level may need to be adjusted.
Injection mode
For low speed sensorless operation with signal injection (Sensorless Low Speed Mode (C15) = 0) it is necessary to have a ratio of Lq/Ld = 1.1. Even
if a motor has a larger ratio on no load, this ratio normally reduces as the q axis current is increased from zero. Sensorless Mode Low Speed Current
(C16) should be set at a level that is lower than the point where the inductance ratio falls to 1.1. The value of this parameter is used to define the drive
current limits when signal injection is active and prevent loss of control of the motor.
Non-salient mode
For low speed sensorless operation for non-salient motors (Sensorless Low Speed Mode (C15) = 1) this defines a current applied in the d axis to aid
starting. For most motors and application requiring up to 60 % torque on starting the default value is suitable. However the level of current may need
to be increased to make the motor start.
When sensorless mode is active, the measured speed can include some ripple which increases as the drive passes into field weakening. A filter is
applied to the estimated speed and Sensorless Mode Filter (C17) defines the time constant. The default time constant is 4 ms, but this can be
extended to improve the filtering. This is particularly useful when using standard ramp or spinning start with a low friction high inertia load, and can
prevent over voltage trips when the drive has no braking resistor.
C16 Sensorless Mode Low Speed Current
Mode RFC-S
Minimum 0.0 Maximum 1000.0
Default 20.0 Units %
Type 16 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 1
Coding RW, RA
C17 Sensorless Mode Filter
Mode RFC-A, RFC-S
Minimum 0 Maximum 4
Default 0 Units
Type 8 Bit User Save Update Rate Background read
Display Format Standard Decimal Places 0
Coding RW, Txt
Value Text
04
18
216
332
464
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