Soken DAC-HRI-3N - 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-3 can measure resistances of the coil winding of a motor-driven inverter power supply (PWM) during applying voltage.

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 the temperature rise test of the motor. Comparing these 2 methods, the former one is easily influenced by environmental temperature. DAC-HRI-3, introducing the later method, can measure the resistance of the coil windings directly and obtain precise resistance values. Besides, DAC-HRI-3 can measure resistance without turning off the power, it enables you to have the true temperature of a whole driven motor coil efficiently.

Test Materials

• EV 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

Option Items

• Auto 3-Phase switching unit model DAC-SCB-3
• DC Cut Capacitor Box for 3 phase measurement (From 2A to 450A or more, please specify the test current)

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.

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

Connection diagram for DAC-HRI-3 and the capacitor box DAC-C23AXC7A-SC

(The diagram is when 7A is used)
Manually select the test phase (U-V, V-W or W-U) from the switch on the front of the capacitor box.

Connection diagram for DAC-HRI-3, DAC-SCB-3, and the capacitor box DAC-C45AXC7A-C

By using the 3-phase switching unit DAC-SCB-3 and software, continuous measurement is possible while automatically switching each phase (U-V, V-W, W-U) at optional interval time through PC.

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 the specimen.

• Capacitor: Electrolytic Capacitor
• Maximum-allowed-current value:
  • 470µF … 2A
  • 4,700µF … 7A
  • 47,000µF …23A
  • 330,000µF …45A

Model DAC-C23AXC7A (For 3 Phase 23A/7A)

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

About Hot-Line resistance measurement

The conventional temperature rise test of motors has to be turned off the power every time to measure the resistances. However, a coil cools rapidly and its resistance also changes promptly once turning off the power. In case a fan is equipped with a motor, the motor exterior is cooled by the fan, and there could be large differences with the actual temperature of the coil inside the motor. SOKEN Hot-Line resistance meters can measure resistance without turning off the power, and changes of resistance at the real time can be obtained. DAC-HRI-3 is an ideal meter to achieve the true temperature of a whole driven motor coil efficiently.

Why superimpose a DC component on the AC line

It is not impossible to derive effective resistance from AC components under the energized state, but the derivation is associated with difficulties related to load conditions or separation of iron loss. In addition, pertinent electrical regulations stipulate that copper wire resistance must be DC measured. For this reason, this Coil Resistance Meter adopts the approach of superimposing a DC component on the AC line. The magnitude of the DC current to be superimposed, however, is made negligible to the AC current.

Test Materials

• EV 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

Option Items

• Auto 3-Phase switching unit model DAC-SCB-3
• DC Cut Capacitor Box for 3 phase measurement (From 2A to 450A or more, please specify the test current)

Option Switching Box DAC-SCB-3 with Software for AUTO 3-phase measurement

• 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. 

Measuring Range

Resolution

Display

Accuracy

Input Impedance

Accessories

General

*Max 700V type is available as option. (Model DAC-HRI-3 Type 700)

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.