General Requirements On Using; Rd Party Pmsm Motors With Sinamics Drives; Motor Run-Up; Explanation On Inductances Ld, Lq - Siemens SINAMICS G120X Commissioning Manual

2 General conditions of operation
2.3

General requirements on using 3

SINAMICS drives
General requirements on 3rd party motors and their operations are described in the document
SINAMICS S120 Requirements placed on third-party motors:
https://support.industry.siemens.com/cs/ww/en/view/109760445
Most important are:
•
Motor insulation system – check requirements regarding voltage stress. If needed use
dv/dt filter.
•
BEMF waveform – must be sinusoidal ideally up to 2% THD.
•
Low cogging torque – up to 4% peak-peak value compared to rated torque.
•
Rated motor voltage – this should be ideally ≤ 0.9 x inverter supply voltage otherwise
derating may apply.
•
Pulse frequency – depending on frame size and/or voltage rating the standard pulse
frequency of G120X inverters is either 4kHz or 2kHz. The motor must be of a suitable
design for this.
2.4

Motor run-up

During operation the rotor position is derived from known motor parameters and measured
quantities (voltage and current).
1. At every drive enable the initial rotor position is measured indirectly. This is called Pole
Position Identification (PolID). As default a sequence of voltage pulses is sent to the
motor phases, this results in a current increase which is evaluated to determine the pole
positions. This results in a short delay of approx. 200ms during which a "humming"
noise can be heard from motor.
2. The acceleration phase then follows with an injected current 10% more according to the
maximum expected load.
3. Once the speed reaches the value defined by p1755 (Motor model changeover speed
encoderless operation) the inverter operation switches to closed-loop mode providing
highly efficient motor control.
Note that motor operation in the open-loop phase is utilized only for transient conditions i.e. start
of acceleration or end of deceleration. The motor minimum operating speed (p1080) must
always be greater than Motor model changeover speed!
2.5

Explanation on inductances Ld, Lq

Ld – direct inductance and Lq – quadrature inductance. These motor parameters represent the
motor inductance when the rotor is positioned either in direct or in quadrature axis.
Direct axis is where the rotor magnetic axis is aligned with stator magnetic axis.
Quadrature axis is where the rotor magnetic axis is at an angle = (90°/pole-pair number) with
respect to the stator magnetic axis. That means 90° electrical.
Non equality between Ld and Lq indicates that a reluctance torque may be present in the motor.
This must be taken into account in the motor control to optimize efficient operation – MTPC
(Maximum Torque Per Current)
User experience shows the best results can be expected when the Ld, Lq difference is less than
20% like in case of SMPM.
G120X commissioning guide for permanent magnet motors PMSM
Entry-ID: 109780815, V1.0, 07/2020
rd
party PMSM motors with
6