IVT 09LR-N Service Manual page 20

Split type air to air heat pump

Table of Contents

12LRN

4. 120 energizing control (digital position detection control)

This control system detects the digital position detection signal and adjusts the rate of acceleration/deceleration accordingly.

The motor's induced voltage waveform is input to the comparator in the form of PWM-switched pulse waveform, and a position detection signal is

generated as a reference voltage equaling 1/2 of 280 VDC. However, since there is no induced voltage waveform when the PWM waveform is OFF,

the microcomputer performs internal processing so that detection is enabled only when it is ON. Based on the detected position signal, actual PWM

waveform output timing is determined. Since it does not use a filter circuit, the detection accuracy is high.

The microcomputer performs internal processing to cancel spike voltage during the regenerative process.

Furthermore, even if the induced voltage is low, position detection is still possible, thus allowing sensor-less operation at low rotation speed in the ini-

tial stage of operation. This reduces the starting current and improves the IPM reliability.

Spike voltage

(cancelled)

5. 180 Energizing Control

This is the control system to moderate the speed by the current phase difference for higher efficiency and lower noise of the compressor. The current

phase difference control is the control system paid attention to the interrelation between efficiency and phase gap generated by the applied voltage of

motor and current in the coil of motor as shown in the figure below.

This control is the V/F drive system independent of the location of rotor, detecting the phase difference between driving voltage phase and line current

phase flowing in motor coil, and controls the modulation rate data to get the phase difference at the best efficiency.

Terminal voltage waveform

Motor voltage

Motor current

Difference of current

Best timing

and voltage peak

Concept chart of the current phase difference control

Reference voltage

(1/2 of DC voltage)

Comparator output waveform

(Position signal waveform)