690V 800KW-2000KW Frequency Converter for Oilfield Drilling Pumps

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* Torque and flux can be changed very fast by changing the references
* High efficiency & low losses - switching losses are minimized because the transistors are switched only when it is needed to keep torque and flux within their hysteresis bands
* The step response has no overshoot
* No dynamic coordinate transforms are needed, all calculations are done in stationary coordinate system
* No separate modulator is needed, the hysteresis control defines the switch control signals directly
* There are no PI current controllers. Thus no tuning of the control is required
* The switching frequency of the transistors is not constant. However, by controlling the width of the tolerance bands the
average switching frequency can be kept roughly at its reference value. This also keeps the current and torque ripple small.Thus the torque and current ripple are of the same magnitude as with vector controlled drives with the same switching frequency.
* Due to the hysteresis control the switching process is random by nature. Thus there are no peaks in the current spectrum. This further means that the audible noise of the machine is low
* The intermediate DC circuit's voltage variation is automatically taken into account in the algorithm (in voltage integration).Thus no problems exist due to dc voltage ripple (aliasing) or dc voltage transients
* Synchronization to rotating machine is straightforward due to the fast control; Just make the torque reference zero and start the inverter. The flux will be identified by the first current pulse
* Digital control equipment has to be very fast in order to be able to prevent the flux and torque from deviating far from the
tolerance bands. Typically the control algorithm has to be performed with 10 - 30 microseconds or shorter intervals. However, the amount of calculations required is small due to the simplicity of the algorithm
* The current measuring devices have to be high quality ones without noise because spikes in the measured signals easily cause erroneous control actions. Further complication is that no low-pass filtering can be used to remove noise because filtering causes delays in the resulting actual values that ruins the hysteresis control
* The stator voltage measurements should have as low offset error as possible in order to keep the flux estimation error down. For this reason the stator voltages are usually estimated from the measured DC intermediate circuit voltage and the transistor control signals
* In higher speeds the method is not sensitive to any motor parameters. However, at low speeds the error in stator resistance used in stator flux estimation becomes critical

Inverter motor type must be a three phase AC induction motor. Preferably, you should use an inverter-grade motor that has 800V insulation for 200V class inverters, or 1600V insulation for 400V class inverters. For motor size, in practice it is much better to find the right size motor for your application; then look for an inverter to match the motor.

The EPRI Power Industry Study by General Electric in 1985 offered the following causes based on 6,000 utility motor failures: 41% were bearing related, 37% were stator related, 10% were rotor related and 12% were other causes.

The EPRI Power Industry Study by General Electric in 1985 offered the following causes based on 6,000 utility motor failures: 41% were bearing related, 37% were stator related, 10% were rotor related and 12% were other causes.