7224RLY: Up to 52 Ap Current Source


For Protection Relay Production Testing and Commissioning

  • High compliance voltage allows the 7224RLY to drive electromechanical relays directly
  • Maintains phase accuracy for any load from a dead short to 2 ohms
  • Front panel indicators for rapid assessment of amplifier status
  • Protection circuitry protects from input overloads, improper output connection (including shorted and improper loads), over-temperature, over-current, and supply voltages that are too high or low

Key Performance Capabilities:

  • Up to 50 Ap (35A RMS) output power at 0.5 ohms
  • Up to 158 Vp output voltage
  • Standard transconductance of 20 ±0.2% from short to 1-ohm load
  • Residual noise of less than 2.5 mA peak, from 40 Hz to 600 Hz

The 7224RLYwas created to meet the demanding requirements of the power utility industry. Capable of outputting a 40 mSec pulse with up to 52 amperes peak current, the 7224RLY is powerful enough to put protection relays, fuses and other critical components through a full range of tests. The low noise floor, low distortion and minimal phase error of the 7224RLY make it the ideal amplifier for power grid modeling.


Pulse/Burst Specifications

Note: Testing performed in mid-level mode using 40 ms pulses with a 30% duty cycle.




1.0 ohms 5 minutes 60 Hz Sine 28A RMS / 40A peak
DC 20A peak
20 seconds 60 Hz Sine 30A RMS / 43A peak
DC 20A peak
0.2 seconds 60 Hz Sine 33A RMS / 47A peak
DC 30A peak



Current Output


Amplitude vs. Frequency at 1V input, 20A output,
amplifier transconductance set to 20:

Load Input Signal Transconductance
1 kHz 100 Hz
2 ohms Sine 19.9 20
1 ohm Sine 20 20
0.5 ohm Sine 20 20
Short* Sine 20 20

*Unimpeded wire.

Front & Back

7212 Front Panel



Controlled-Current Bandwidth (0.25-ohm load): DC to 10 kHz
Maximum Output Current (0.5-ohm load): 35A RMS (50 Ap)
Maximum Output Voltage: 158 Vp
Maximum Output Power:: Dependent on load and frequency
Load Constraint for Maximum Output: 0.5 ohms + 200 mH (Note: all loads from 8-ohm to short are stable with 2 mH in series)
Output Offset Current: Less than 10.0 mA DC peak
Standard Transconductance (from short to 1-ohm load): 20 ±0.2%
Common Mode Rejection Ratio (40 to 600 Hz): -58 dB minimum
Unit-to-Unit Phase Error (60 Hz): ±0.1 degrees
Residual Noise (40 to 600 Hz): Less than 2.5 mA peak
Input-to-Output Phase Delay: -0.2 degrees
Out Accuracy: Less than ±1%

Input Characteristics

Balanced with ground: Three terminal barrier block connector, 20k ohm differential
Unbalanced: BNC connector, 10k ohm single ended.
Max Input Voltage: ±10V, balanced or unbalanced
Common Mode Rejection: -58 dB with 5V input

Status Display, Control, I/O

Front Panel LED Displays indicate: Ready, Standby, Fault, Over Temp, Over Voltage, Overload
Soft Touch Switches for: Run, Stop, Reset
Gain Control, when enabled: Voltage gain adjustable from 20 to 0
On/Off Breaker
Back Panel Power Connection: 25 Amp IEC (with retention latch)
Signal Output: Three-position terminal strip (OUTPUT/COM/CHASSIS GROUND)
Signal Input: User Selectable BNC or Barrier Strip, Balanced or Unbalanced

Communication Capabilities

Current Monitor: 5A/V ± 1%; 2.5A/V ± 1% (differential configuration)
Reporting: System Fault, Over Temp, Over Voltage, Over Load
Remote Control via Interlock Connector: Force to Standby, Reset after a fault


Over/Under Voltage:
± 10% from specified supply voltage amplifier is forced to Standby
Over Current:
Breaker protection on both main power and low voltage supplies
Over Temperature:
Separate Output transistor, heat sink, and transformer temperature monitoring and protection

Physical Characteristics

The Amplifier is designed for stand- alone or rack-mounted operation. The Chassis is black aluminum with a powder coat finish. The unit occupies two EIA 19-inch-wide units.
Weight: 41 lbs (18.6 kg), Shipping 51 lbs (23.2 kg)
AC Power: Single phase, 120 VAC, 60 Hz, 10 Amp service; (220-240 VAC, 50-60 Hz, 10 Amp service model available)
Operating Temperature:
10°C to 50°C (50°F to 122°F), maximum output Power de-rated above 30°C (86°F).
Humidity: 70% or less, non-condensing
Cooling: Forced air cooling from front to back through removable filters.
Airflow: 180CFM
Dimensions (HxWxD): 3.5” x 19” x 22.75” (8.9 cm x 48.3 cm x 57.8 cm)


7224RLY Datasheet

Complete technical specifications

7224/7226 Operator's Manual

General Operation for 7212/7224/7224RLY and 7226 models

Operator's Manual Supplement

For 7224RLY amplifiers

SIM Pinouts and Functions

For 7212, 7224, 7224RLY, 7226, 7548, 7548RLY, 7794, 7796 and 7796RLY amplifiers

DXF Model for Chassis

For 7212, 7224, 7224RLY and 7226 amplifiers

STEP file for Chassis

For 7212, 7224, 7224RLY and 7226 amplifiers

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