Sensorless Control

Dynamics, simplicity, reliability: These fundamental goals of every drive system can be achieved with customized sensorless speed control. Celeroton provides various technologies in order to optimally cover your needs.

To enable field orientated control of permanent magnet synchronous motors (PMSM) and brushless DC motors (BLDC motors) the angle of the rotor magnetic field must be known. Usually Hall sensors or encoders are needed, but now with sensorless-technology from Celeroton these additional parts are now no-longer needed. This brings a lot of advantages. The number of cables and connectors can be reduced, which leads to significant advantages for compact motors used in e.g. spindles for micromachining or medical applications. The mechanical stability and rotor dynamics are also improved and, therefore, the maximum achievable speed is increased since there is no need for additional discs or magnets for the angle sensor. This results in a complete system with higher reliability.

Our converters provide sensorless speed control from standstill to 1 million rpm depending on the combinations of the applied control method - inductivity-based, observer method or zero crossing detection (ZCD) of the back-EMF (BEMF).

Which control method for which motor? There is no general answer to this question. On one hand the targeted speed range excludes some methods; on the other hand the selected modulation scheme of the converter and the control method both influence each other. At the end of the day, some motors match better with one or the other control methods and modulation schemes.

CC-75-500 This is why Celeroton individually adapts the sensorless speed control to your motor. We can offer you two different options to implement our sensorless technology, depending on your specifications and applications: Drive your motor directly with a Celeroton converter or you can integrate and license the sensorless technology directly into your electronics. With various technologies we are able to serve a very wide range of methods:



PAM (block communication) with sensorless speed control (ZCD)
FunctionalityRotor is accelerated open loop up to the synchronization speed, and above that
the rotational speed is controlled in sensorless mode
Minimum speedSynchronization speed (depending on motor type),
between 2,000 and 10,000 rpm
Maximum speed1 million rpm
Particular suitable for     Very high rotational speeds, low phase inductance
AdvantagesLower losses in converter and motor (with low inductances) than with PWM
DisadvantagesHigher rotor losses than with PWM in slotted motors with rotational speeds
below approx. 100,000 to 200,000 rpm
AvailabilityAll Celeroton converters


Six-step with sensorless control (LV-BEMF)
FunctionalityAllows for sensorless control from very low speeds. May easily be combined
with the ZCD-method
Minimum speed> 100 rpm
Maximum speedApprox. 100,000 rpm
Particular suitable for   Cost-efficient solution when designed for specific motors
AdvantagesLow hardware effort
DisadvantagesTorque reduction at higher speeds (if not combined with ZCD)
AvailabilityCustomized solution


PWM (sinusoidal commutation) with sensorless control (observer)
FunctionalityComparable to ZCD method
Minimum speedSynchronization speed (depending on motor) at approx. 4,000 rpm
Maximum speedApprox. 200,000 rpm
Particular suitable for  Speed range of 10,000 to 150,000 rpm and motors with higher phase
inductance (e.g. slotted motors)
AdvantagesLeads to lower motor losses than PAM or Six-step with the same motors
DisadvantagesMay lead to higher converter losses. Higher computing power required than
other sensorless methods
AvailabilityCC-75-500, CC-100-1000


PAM (block commutation) with sensorless control from standstill (SL2Z with interruption in torque)
FunctionalityMethod with short-term torque interruption under operation, allows for sensorless
speed control from standstill
Minimum speedStandstill
Maximum speedUsually used in combination with sensorless control (ZCD) resulting in a
maximum speed of 1 million rpm
Particular suitable for     Applications requiring full torque from standstill
AdvantagesFull torque from standstill
DisadvantagesTorque ripple, noise generation and interuption in torque
Motor has to meet specific requirements, especially concerning asymmetry in
inductance. Can be checked by Celeroton


PWM (sinusoidal commutation) with sensorless control from standstill (SL2Z without
interruption in torque)
FunctionalityAllows for sensorless speed control from standstill, PWM without interruption in
torque, higher angle resolution
Minimum speedStandstill
Maximum speedApprox. 100,000 rpm
Particular suitable for    Applications with full torque within a wide speed range from standstill up to high
rotational speeds
AdvantagesTorque ripple is low to non-existant, reliable and jerk-free also at lowest speeds
DisadvantagesAdditional output filter and analog electronics needed. Limits maximum
rotational speed
AvailabilityCustomized converters
Motor has to meet specific requirements


There are different possibilities to test your application with
our control methods. Purchase or rent a test converter, with
commissioning at Celeroton or directly at your facility.