Mode 1: V/F control for constant torque loads with Meiden Advanced Torque Control
This mode uses auto-tuning to give voltage vector control in open loop. The main features of this mode are:
a) Built-in PID controller eliminates the requirement -and cost -of a separate device.
b) Tripless operation.This safe and convenient feature is a combination of:

• the ability to dynamically extend ramp times during operation if the load is likely to demand too high a current or regenerate a higher current than the programmed limit;
• automatic limiting of the IGBT switching frequency if the heatsink temperature rises too high;
• the ability to limit current transients caused by shock loads;
• alarms and controlled shutdown in the event of a fault which is non- life threatening for the drive or motor.

Mode 2: V/F control for variable torque loads with Meiden Advanced Torque Control
This Mode uses auto-tuning to give voltage vector control in open loop with the added benefit that,because of a higher continuous current rating than in constant torque mode,an inverter of one size lower may be used in order to reduce the purchase cost.
Features include:
a) Special energy saving features for fans and pumps where V/F ratios are dynamically controlled to optimise the power usage.
b) The drive can auto-tune to two independent motors,so that one inverter can be used in applications such as pumping where a main and standby pump are fed by the same source.
c) Multi-pump control.This is a logic control system commonly used where two or more pumps maintain pressure in a system,one being variable speed and the others being brought in as required.

Mode 3: Sensorless Vector Control
There are many drives which claim to offer sensorless vector control but Meiden feel that this term is misused and describes a control system similar to Meiden's standard Advanced Torque Control.Meiden define true Sensorless Vector Control as Flux Vector Control without an encoder.

Closed loop vector control requires the use of an encoder so that shaft position can be used in order to calculate and control phase angle and shaft speed. Because of this,all settings within a closed loop environment relate to actual shaft rotation rather than output frequency.

Meiden have developed a method whereby the shaft rotation can be calculated by very closely monitoring the waveform and feedback at the three output phases of the drive.All of the settings within the VT230S in sensorless vector mode are therefore set using rotational speed and not output frequency.

In addition,Meiden incorporate two current loops to control magnetising current independently.Thus,the VT230S can perform almost as well as a closed loop system and uniquely provide torque at zero speed (see FIG.1).

'Motor Loss Braking'is a system which reduces motor efficiency during regenerative braking allowing some of the braking energy to be dissipated from the motor as heat,so reducing the size (or even eliminating)the brake resistor.

Mode 4: Closed Loop Vector Control
This advanced mode enables motor speed to be varied across a 1000:1 speed range,with 0.01%accuracy up to 6 times faster than conventional drives (30Hz response time).

In addition to outstanding torque performance,this mode contains a new feature whereby the loss of the encoder signal will cause the drive to automatically switch into Sensorless Vector mode.The drive then issues an alarm signal which can be used as an indication or as a shutdown signal.

Closed Loop Vector Control requires a Meiden V23-DN1 or V23-DN2 Encoder Feedback card.

Mode 5: PM Motor Control
This mode enables the use of ultra- efficient PM motors for energy conservation.Meiden PM motors are available in standard IEC frame sizes (rather than servo-type square frames) which are rated in kW and directly interchangeable with squirrel cage motors.This technology,where Meiden parent company Meidensha are at the leading edge,can offer energy savings of up to 15%compared with the use of standard motors (test results are illustrated overleaf).

In the UK,60%of the nation ’s electrical consumption is used by industrial electric motors.Meiden technology can assist countries reduce their CO 2 emissions in line with the targets set out in the Kyoto agreement.

(PM Motor Control requires a Meiden V23-DN3 Encoder Feedback card.)

Patent applied for

Meiden Soft Sound technology reduces the characteristic whine from inverter- driven motors AND eliminates the side- effects of conventional noise reduction methods —specifically that of raising the carrier frequency.

Soft Sound varies the carrier frequency in one of two fixed patterns,from a user-selected base frequency (between 2.1kHz and 5kHz).By keeping the carrier frequency range low,torque performance is notably better than a high-frequency carrier.

The high frequency induced problems of hot running,degrading of winding insulation,arcing across motor bearings, high leakage currents and interference are eliminated.

Encoder feedback cards
V23-DN1 12V A/B phase 60kHz;6V ingle phase 20kHz;12V DC 100mA supply output
V23-DN2 5V A/B phase differential 250kHz;5V DC 200mA supply output
V23-DN3 5V 6 phase (ABZUVW)250Hz for permanent magnet motors;5V DC200mA supply output

Communication cards
V23-PIO 16-bit parallel communications
V23-SLO RS232/485 serial communications
V23-SL6 Profibus interface slave station Relay interface
V23-RYO 4x ink/source input PS16-9; 2x contact output PS04-5
Brake resistor Internal for drives up to 7.5kW External for all drives

It has long been known that Permanent Magnet Motors offer efficiency advantages over standard 3-phase motors. By using a magnetised rotor,a proportion of the drive ’s energy is not wasted inducing a magnetic field.Because less energy is wasted,less heat is created and in many applications,there is no need for a cooling fan.

Meiden PM Motors are assembled in standard IEC-size frames for easy retro- fit and interchange with 3-phase motors, Specifying is made easier by rating each motor in kW (rather than Nm). The efficiency of Meiden PM Motors often enables a motor one size smaller to be specified.

In its standard form,with no option cards fitted,the Meiden VT230S is a highly specified and surprisingly economical drive.Standard features include a built-in PID controller,IP54 detachable keypad with Memory/Drive Cloning function; Meiden Soft Sound to reduce motor running noise;energy saving options; and power loss braking.

With option cards fitted,the basic drive operates at the leading edge with unprecedented smoothness and safety.Matched with Meiden PM Motors,VT230S represents the ultimate in motor and control technology.