Soken DAC-HRI-3N TYPE 700 - Invertor Hot Line Coil Resistance Meter

**In response to requests for an expanded measuring ranges, DAC-HRI-3N series support the resistance range from 0 to 4000Ω. 
(DAC-HRI-3 series supported up to 2000Ω.)**

DAC-HRI-3N TYPE 700 can measure resistances of coil windings of a motor driven by inverter power supply (PWM) during applying voltage (Max AC 700V).

Generally, either the temperature measuring method which measures a partial temperature by using temperature sensor, or the resistance method which measures resistance and converts it by using temperature coefficient, is introduced to temperature rise test of motor. DAC-HRI-3 TYPE 700, introducing the resistance method, can measure resistance of the coil windings directly, and obtain precise resistance values without turning off the power. The HOT LINE Resistance meter enables you to have the true temperature of a whole driven motor coil simply and efficiently.

Test Materials

• EV Motor, HEV Motor
• Brushless Motor
• Compressor Motor for Air-Conditioner

Rerated Standard

• JIS C4203 Single Phase induction motors
• JEC 2137 Induction motor
• JEC 60034-1 Rotating electrical machines - Part 1: Rating and performance

Principals

A DC-blocking capacitor is inserted to prevent flow of the DC measuring current into the AC power source, and the energizing AC voltage is applied to the coil, Lx, of the tested motor. A DC current from the DC constant current circuit of the Coil Resistance Meter is superimposed on the coil, Lx, and the voltage drop across the Lx is measured. The DC component of the measured voltage drop is extracted by using a low pass filter (LPF), and then the coil resistance is calculated and displayed. Because the LPF is composed of circuit elements, a CPU-based digital filter is used to eliminate inverter noises.

Conversion to temperature

Usually, 1/α0 = 234.5, where α0 is the temperature coefficient at 0ºC, is used for the conversion to temperature as described in the following formula.

tc = Rt – Rt0 / Rt0 (234.5 + t0) + t0

∆t = tc-te

tc = Converted Temperature ( Tc )

∆t = Temperature Rise ( ∆T )

te = Ambiant Temperature ( Te )

Rt = Measured Electrical Resistance ( R )

Rt0 = Initial Resistance ( R0 )

t0 = Initial Temperature ( T0 )

 

Free-Software

Conversion to Temperature is possible by input the Initial Resistance value and initial Temperature value through PC by using a free-software. Measured values with time are saved and displayed in an Excel Sheet. 

DC Blocking Capacitors Box

DC Blocking Capacitor must be required for measurement under energized. An appropriate capacitor must be selected in accordance with the rated current of specimen.

Optional Capacitors for single phase, 3-phase, and large current specification etc, are also available.

Necessity of Hot-Line resistance measurement

During the temperature rise test of a coil, in particular, a coil of small-size equipment cools rapidly once de-energized, and so its resistance changes considerably. In other words, it is very difficult to accurately measure the coil resistance of a running motor. In the case of the coil of a motor that is equipped with a fan, the motor exterior is cooled by the fan, but the temperature of the coil inside the motor can be much higher. In this case, the motor temperature that is measured externally with, for example, a thermistor, can be much different from the temperature of the coil. The traditional “measurement of coil resistance after shutdown” is based on the assumption that the temperature rises and falls in accordance with natural logarithm, but the assumption often fails for products of complicated structure, and differences or errors are inevitable in inferring the coil resistance under the energized state from that under the de-energized state. Therefore, hot-line resistance measurement is an ideal method for correct measurement of coil resistances.

Connecting Diagram

Option Switching Box with Software for AUTO 3-phase measurement

Automatic 3-phase measurement is available with option Switching Box.

Auto Measuring Software (PC display image)

• Continuous Measurement to obtain Temperature Rise – Cooling Curve. 
• Automatic switchover of 3-phase (U-V, V-W, U-W).
• Data acquisition of 1 selected phase at minimum sampling time.
• Time Interval and a number of times of import data are configurable.
• Conversion to Temperature only by input the Initial Resistance value and initial Temperature value.

Connecting Example

Test Materials

• EV Motor, HEV Motor
• Brushless Motor
• Compressor Motor for Air-Conditioner

Rerated Standard

• JIS C4203 Single Phase induction motors
• JEC 2137 Induction motor
• JEC 60034-1 Rotating electrical machines - Part 1: Rating and performance

General

*For test Max 450V, model DAC-HRI-3 is available.

Measuring Range

Resolution

Display

Accuracy

Input Impedance

Dimensions

Do you have a Invertor Hot Line Coil Resistance Meter that needs to be calibrated?

We offer standard traceable calibration and ISO 17025 accredited calibration services.