AC servo / General Inverter (Drives) for Industry

In the application of AC servo and general inverter for industrial machinary, current sensors are used in following three places;
1. Power Factor Correction (PFC),
2. Vector control, and
3. Over current detection.

In this page, we would like to propose you our recommendation of AKM products in each place with its superiority.

1. Power Factor Correction (PFC)

Suppressing harmonics caused by switching

*PFC is a short-term of Power Factor Correction, which means a power factor improvement circuit.

After the establishment of harmonic current regulation, PFC is built in to suppress harmonic current generated in input current caused by switching power supply. 

Since isolation is needed between the primary and secondary side, shunt method (shunt resistor + isolation amplifier) and magnetic currrent sensor with core had been mainly used for current detection in the past.

AKM's current sensor (coreless current sensor) is galvanically isolated by SMT package, so that it can realize the minituarization of the system, the simplification of the circuit, and the reduction of the design man-hours with safety function.

(The structure of AKM package is designed to be optimal for isolation. Please click here for more information about "Creating a Safer System".)

Advantage of AKM products

  • High withstand voltage
  • Fast resonse
  • Good temprature characteristic

Our recommendation

Please refer to the "Selection Table".

2. Vector control

Improve motor efficiency and realise energy-saved and fine-gained torque control

AKM's coreless current sensor is small size and has characteristics of high pressure resistance, high accuracy and superior temprature characteristic. Therefore, it is more efficient than the shunt resistor+isolation amplifier/ADC, and it can achieve system minituarization while maintaing and improving its controllabirity.

In addition, the resitstance value of the primary conductor is small at 0.3m ohm, it is possible to suppress the heat generation and reduce the substrate size.

(Please click here for more information about "System Downsizing".)

Advantage of AKM products

  • High accuracy (Low sensitivity drift)
  • Fast response
  • High withstand volgate
  • Small size
  • Low-heat generation

Our recommendation

Please refer to the "Selection Table".

3. Over Current Detection

For the purpose of  improving safety system and overcurrent protection of switching devices

AKM's coreless current sensor is suitable for overcurrent detection because it is fast response and it can measure to larger curent compared to other companies.

You can use AKM's coreless current sensor in High side as you can see on the block diagram above because it is isolated inside the current sensor IC itself.

By using in High side, the ground fault of the phase current can be detected and the inverter can be protected from the ground fault caused by the disconnection by wrong wiring or aiging

In the configulation of shunt +isolation amplifier, the complexity of the circuit deign by the tempurature correction circuit and the increase of the numbers of parts have been serious problems.

However, if you use AKM's coreless current sensor, you can solve these problems because it can reduce design man-hours and realize total system minituarization by reducing the number of parts and deigning a simple circuit.

(Please click here for more information about "Redusing design man-hours".)

Advantage of AKM products

  • Fast response
  • High withstand voltage

Our recommendation

Please refer to the "Selection Table".

Selection Table

Bipolar /
Voltage *
Product Name Product Series
5.0 5.0 60 ± 5.3 to ± 180
Bipolar ≧ 8 800 CZ370x CZ37 Series
0 to 345.2 Unipolar CZ372x 
3.0 50 ± 11.6 to ± 166.6 Bipolar CZ3AGx CZ3A Series
3.3 3.3 ± 12.9 to ± 129.1 CZ3A0x
5.0 5.0 40 ± 33 to ± 60 ≧ 7.2 715 CZ381x CZ38 Series
5.0 5.0 20 ± 4.5 to ± 42 Bipolar
≧ 5 500 CQ330x CQ3 Series
3.3 3.3 ± 8.5 to ± 44 CQ320x
5.0 5.0 ± 10.7 to ± 42 AK310x AK31 Series

* Pollution Degree II with reinforced insulation

'Currentier' series are open-type current sensor ICs which have the world's smallest package, high accuracy, high S/N ratio, and the world's fastest response time.
With these advantages, we will offer the best current sensing solution to wide-ranging applications, such as inverter control, overcurrent detection, and electrical power detection.

* Currentier is a trademark of Asahi Kasei Microdevices Corporation.